Brody Myopathy

Mendelian MONDO:0010977 Pathograph 30 Show in embeddings browser

Brody myopathy is an autosomal recessive skeletal-muscle relaxation disorder caused by biallelic pathogenic ATP2A1 variants. Deficient SERCA1 abundance or calcium-transport function impairs calcium reuptake into the sarcoplasmic reticulum, particularly in fast-twitch muscle fibres. Exercise-induced stiffness and delayed relaxation usually begin in childhood, often affecting limbs and eyelids. Myotonic discharges are generally absent despite clinically evident contractures. Strength and bulk are usually preserved, but mild weakness, percussion myotonia and limited symptom progression are reported. Rhabdomyolysis and anesthesia-associated contractures warrant perioperative precautions; classic malignant hyperthermia susceptibility is not established for every patient. Experimental protein-rescue strategies apply to selected functionally competent mutant pumps and have not established clinical efficacy in humans.

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Inheritance

Autosomal recessive HP:0000007

Biallelic pathogenic ATP2A1 variants cause autosomal recessive Brody disease. Heterozygous relatives in reported families generally lack the Brody phenotype. When both parents carry one familial pathogenic allele, each pregnancy has the standard recessive recurrence risk of 25%; molecular phasing and family testing are important for counseling.

Autosomal recessive inheritance

Show evidence (2 references)

PMID:8841193 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"We have now associated Brody disease with the autosomal recessive inheritance of three ATP2A1 mutations in two families"

Founding human genetic evidence establishes recessive ATP2A1 causation.

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Heterozygous family members of patients (carriers) did not exhibit the Brody disease phenotype"

Family histories support unaffected carriers, although carrier phenotyping was not systematically collected.

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Mechanistic Hypotheses

Alternative calcium extrusion contributes to compensation

pmca_extrusion_compensation EMERGING

Evidence balance 1 support

Increased sarcolemmal calcium-pump expression and altered mitochondrial-marker distribution in one affected calf support alternative calcium handling as a candidate adaptation. Protein abundance does not directly measure flux or demonstrate rescue. This mechanism can coexist with SERCA2 adaptation.

Direct human functional confirmation remains lacking in the cited studies.

Pathograph links

Impaired Calcium Reuptake into the Sarcoplasmic Reticulum -> Compensatory Calcium Extrusion and Handling INDIRECT UNKNOWN INTERMEDIATES Alternative calcium-handling responses may compensate for the primary deficit; the contribution varies between models and patients.

Show evidence (1 reference)

PMID:26482047 SUPPORT INDIRECT PRIMARY RESULT Model Organism

"pathological muscles are characterized by a broad distribution of mitochondrial markers in all fiber types, not related to intrinsic features of double muscle phenotype and by an increased expression of sarcolemmal calcium extrusion pump."

One affected calf shows altered protein-marker expression; increased calcium flux and a causal rescue of severity were not directly demonstrated.

SERCA2 upregulation contributes to compensation in some patients

serca2_isoform_compensation EMERGING

Evidence balance 1 support 2 refute

One human index-patient biopsy showed increased SERCA2 abundance and expression in fast as well as slow fibres. Most other biopsies did not show increased SERCA2. The evidence supports a possible patient-dependent response, not a universal mechanism or an independently refuted observation.

Pathograph links

Show evidence (3 references)

PMID:25614869 SUPPORT INDIRECT PRIMARY RESULT Human Clinical

"Analyses of affected muscles showed the absence of SERCA1, but SERCA2 upregulation in slow and fast myofibers, suggesting a compensatory mechanism that partially restores the diminished Ca(2+) transport in Brody myopathy."

In one index-patient biopsy, increased SERCA2 abundance and ectopic staining support a candidate adaptation; restoration of flux was inferred.

PMID:32040565 REFUTE DIRECT PRIMARY RESULT Human Clinical

"The presence of the SERCA2 isoform was determined by immunohistochemistry in eight biopsies, with normal expression in seven patients and increased expression in one patient"

The cohort includes previously published cases and limits universality; it is not an independent failure to reproduce every original observation.

PMID:26482047 REFUTE INDIRECT PRIMARY RESULT Model Organism

"The reduced expression of SERCA1 is selective and not compensated by the SERCA2 isoform."

The affected calf did not show SERCA2 compensation; this does not rule out human patient-specific adaptation.

Discussions and Knowledge Gaps

Which calcium-handling adaptations preserve muscle function in humans with severe SERCA1 deficiency?

KNOWLEDGE GAP OPEN brody_compensation_mechanism

Attached to

pathophysiology#Compensatory Calcium Extrusion and Handling

One affected human biopsy showed increased SERCA2, whereas most tested biopsies did not. An affected calf showed increased PMCA expression and altered mitochondrial-marker distribution without SERCA2 compensation. These are expression-level observations rather than selective functional-rescue experiments. The candidate mechanisms need not compete exclusively and could vary by patient, fibre type or genetic background.

Proposed experiments

Calcium-handling protein profiling in genotyped Brody muscle

brody_compensation_profiling

Quantify SERCA2, PMCA and other candidate calcium-handling proteins in genotyped patient muscle, and measure calcium clearance with selective perturbations where feasible. Stratify by fibre type and residual SERCA1 function to distinguish expression changes from functional compensation.

Fibre-type-resolved single-nucleus RNA sequencing of Brody muscle

brody_single_nucleus_rnaseq

Compare fibre-type-resolved transcriptional programs in patient muscle and controls, followed by protein and calcium-flux validation. Transcript abundance alone would not establish a compensatory transport mechanism.

Show evidence (2 references)

PMID:32040565 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"Future research would be needed to test if similar compensatory mechanisms can be identified in patients with Brody disease."

The cohort identifies the remaining translational gap.

PMID:26482047 SUPPORT INDIRECT PRIMARY RESULT Model Organism

"Calcium removal mechanisms, operating in muscle fibers as compensatory response aimed at lowering excessive cytoplasmic calcium concentration caused by SERCA1 deficiency, could explain the difference in severity of clinical signs."

The bovine authors frame compensation as a proposed explanation rather than a proven cause.

Why is constitutive SERCA1 loss neonatally lethal in mice while human Brody disease usually permits long-term survival?

HUMAN MODEL MISMATCH OPEN brody_mouse_model_mismatch

Attached to

pathophysiology#Compensatory Calcium Extrusion and Handling pathophysiology#Reduced SERCA1 Density at the Sarcoplasmic Reticulum Membrane

The null mouse has severe diaphragm dysfunction, reduced transport and no detected compensatory expression changes. Human disease includes severe protein deficiency but usually a much milder clinical course. Species-specific diaphragm composition, residual function and alternative calcium-handling responses are plausible, nonexclusive contributors; none alone has been established as the explanation.

Proposed experiments

Hypomorphic Atp2a1 mouse allele series matched to human residual activity

brody_hypomorphic_mouse

Compare graded or conditional Atp2a1 loss with human residual protein and activity measurements, including diaphragm fibre composition and calcium clearance. This could distinguish neonatal complete-loss effects from variant- and species-dependent adaptation.

Show evidence (2 references)

PMID:12556521 SUPPORT DIRECT PRIMARY RESULT Model Organism

"SERCA1-null mice had progressive cyanosis and gasping respiration and succumbed from respiratory failure shortly after birth"

Direct evidence for the model-specific lethal phenotype.

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Onset begins in childhood and there was no or only mild progression of symptoms over time."

Human cohort contrast; does not establish that all patients lack respiratory involvement.

How specifically does reduced compound muscle calcium-ATPase activity identify ATP2A1-related Brody disease?

KNOWLEDGE GAP OPEN brody_assay_specificity

Attached to

biochemical#Sarcoplasmic reticulum calcium ATPase activity

The optimized assay separated four genetically confirmed patients from 28 healthy controls, but it includes SERCA1/SERCA2 and possible PMCA contributions. Other myopathies, muscle site, age, sex and disuse may alter results; clinical sensitivity and specificity require broader validation.

Show evidence (1 reference)

PMID:41938373 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Future research on SERCA activity in these subject groups is needed to determine the specificity of abnormal SERCA activity."

The study explicitly identifies the disease-specificity gap.

⚙

Pathophysiology

Biallelic ATP2A1 Loss of Function

Biallelic pathogenic variants reduce SERCA1 abundance, stability or intrinsic calcium-transport function. Truncating alleles, exon/gene deletions, splice changes, in-frame deletions and missense substitutions are reported. Mechanisms overlap and cannot be assigned solely from variant class; for example, a splice variant causes an in-frame exon skip.

ATP2A1 hgnc:811

SERCA1 calcium transport GO:0005388 ↓ DECREASED

Downstream

Proteasomal Degradation of Misfolded SERCA1 Selected missense variants increase proteasomal disposal of a catalytically competent pump.

Reduced SERCA1 Density at the Sarcoplasmic Reticulum Membrane Loss of expression or stability lowers pump abundance in patient muscle.

Intrinsic SERCA1 Calcium-Transport Defect Some substitutions directly impair calcium affinity and transport.

Show evidence (2 references)

PMID:8841193 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"We have now associated Brody disease with the autosomal recessive inheritance of three ATP2A1 mutations in two families"

Founding human genetic evidence establishes recessive ATP2A1 causation.

PMID:37332993 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"we observed the skipping of the whole Exon 4"

Blood RNA analysis supports the splice effect of c.324+1G>A; the resulting transcript preserves the reading frame.

Proteasomal Degradation of Misfolded SERCA1

Bovine R164H and G211V SERCA1 variants are prematurely ubiquitinated and degraded despite retaining catalytic activity. Mutant protein can reach ER/SR membranes; the evidence supports accelerated disposal, not an obligatory block before membrane insertion. The extent to which this route applies to individual human variants requires functional testing.

proteasome-mediated ubiquitin-dependent protein catabolic process GO:0043161 ↑ INCREASED

Experimental models

Heterologous bovine SERCA1 instability and corrector assays CELL LINE Tests ubiquitination and protein rescue after proteasome inhibition.

Downstream

Reduced SERCA1 Density at the Sarcoplasmic Reticulum Membrane Accelerated degradation decreases steady-state membrane pump abundance.

Show evidence (3 references)

PMID:36293223 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"After blocking the proteasome using a proteasome inhibitor, we found that the G211V mutant accumulates in cells at levels comparable to those of WT SERCA1."

Proteasome inhibition rescues abundance of a bovine disease allele; this is not evidence that every human missense allele follows this mechanism.

PMID:36293223 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"Co-localization using anti calreticulin antibodies, a well-known ER marker, confirmed that SERCA1 mutants are correctly targeted to ER"

Microscopy argues against an absolute pre-membrane trafficking block.

PMID:25288803 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"the mutation generates a protein most likely corrupted in proper folding but not in catalytic activity"

R164H experiments distinguish loss of abundance from loss of enzymatic competence.

Reduced SERCA1 Density at the Sarcoplasmic Reticulum Membrane

Reduced or absent SERCA1 protein is a common biochemical finding in tested patient muscle. A normal immunohistochemical stain does not exclude this deficit, and normal abundance would not exclude an intrinsic catalytic defect. SERCA1 is the dominant calcium pump in type II skeletal muscle fibres.

sarcoplasmic reticulum membrane GO:0033017

Experimental models

Heterologous bovine SERCA1 instability and corrector assays CELL LINE Corrector screening measures restoration of mutant protein abundance.

Bovine pseudomyotonia muscle explants OTHER Tests pharmacological restoration of protein abundance in diseased muscle tissue.

Animal models

Bovine congenital pseudomyotonia: Chianina and Romagnola ATP2A1 variants Cattle partially recapitulates Models low SERCA1 abundance in skeletal muscle, with variant- and species-specific limits.

Downstream

Impaired Calcium Reuptake into the Sarcoplasmic Reticulum Fewer functional pumps reduce the capacity for calcium reuptake.

Selective Type II Fibre Involvement The fast-twitch distribution of SERCA1 helps explain preferential type II pathology.

Show evidence (2 references)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"All immunoblot analyses demonstrated absent or severely decreased amounts of SERCA protein."

Human muscle analyses support reduced protein abundance in the tested patients; abundance and intrinsic function are distinct.

PMID:20142766 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Immunoblotting after high-resolution 2-dimensional gel electrophoresis showed a significant difference in the amount of SERCA1 protein between the patient and controls."

Human muscle protein analysis complements the calcium-ATPase assay.

Intrinsic SERCA1 Calcium-Transport Defect

The human p.Pro789Leu substitution markedly reduces calcium affinity and calcium transport in transfected HEK293 cells despite readily detectable expression. This route is distinct from premature degradation of an otherwise competent pump. Functional defects may coexist with reduced abundance in patient tissue.

P-type calcium transporter activity GO:0005388 ↓ DECREASED

Experimental models

HEK293 expression of human SERCA1 P789L and R819C CELL LINE Tests intrinsic transport impairment separately from protein abundance.

Animal models

accordion zebrafish, including atp2a1 tq206 S766F Zebrafish partially recapitulates S766F is a useful contrast to unstable, activity-retaining mutants; preserved expression and lack of corrector response are consistent with a functional defect.

Downstream

Impaired Calcium Reuptake into the Sarcoplasmic Reticulum Lower transport activity limits calcium reuptake even when mutant protein is present.

Show evidence (1 reference)

PMID:10914677 SUPPORT DIRECT PRIMARY RESULT In Vitro

"The Pro789 to Leu mutant was readily expressed in HEK-293 cells, but it demonstrated an almost complete loss of Ca2+ transport activity because of reduced Ca2+ affinity."

The human disease-associated substitution impairs intrinsic transport despite expression in a heterologous assay.

Impaired Calcium Reuptake into the Sarcoplasmic Reticulum

Impaired SERCA1-dependent transport slows return of contraction-associated calcium to the sarcoplasmic reticulum. Human muscle calcium-ATPase assays and mutant animal calcium imaging support this deficit. The assays do not establish normal calcium release or exclude all other secondary calcium-handling changes.

Alternative calcium extrusion contributes to compensation SERCA2 upregulation contributes to compensation in some patients

calcium ion import into sarcoplasmic reticulum GO:1990036 ↓ DECREASED

Animal models

Bovine congenital pseudomyotonia: Chianina and Romagnola ATP2A1 variants Cattle partially recapitulates Reduced calcium-ATPase activity in affected muscle models loss of reuptake capacity.

accordion zebrafish, including atp2a1 tq206 S766F Zebrafish partially recapitulates Recapitulates impaired calcium clearance after excitation, with species-specific behavioral and developmental readouts.

Atp2a1-null mouse Mouse partially recapitulates Recapitulates deficient calcium transport in diaphragm and skeletal muscle despite a much more severe clinical outcome.

Downstream

Prolonged Cytosolic Calcium Elevation Slower calcium removal prolongs the post-contraction cytosolic transient.

Compensatory Calcium Extrusion and Handling Alternative calcium-handling responses may compensate for the primary deficit; the contribution varies between models and patients.

Show evidence (2 references)

PMID:15469975 SUPPORT INDIRECT PRIMARY RESULT Model Organism

"In vivo imaging of muscle Ca2+ transients revealed that cytosolic Ca2+ decay was significantly slower in acc muscle."

Direct calcium imaging in an atp2a1 zebrafish mutant supports impaired post-contraction clearance.

PMID:41938373 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"We were able to provide new reference values and demonstrate marked decreased SERCA activity in Brody disease muscle samples"

An optimized compound calcium-ATPase assay found low activity in four genetically confirmed patients.

Prolonged Cytosolic Calcium Elevation

Prolonged cytosolic calcium elevation sustains activation of the contractile machinery after the electrical stimulus has ended. Calcium-transient prolongation is directly observed in mutant zebrafish; this supports the human relaxation mechanism without proving that every clinical complication has the same immediate cause.

intracellular calcium ion homeostasis GO:0006874 ↕ DYSREGULATED

Downstream

Electrically Silent Muscle Contracture Delayed calcium clearance prolongs muscle contraction after excitation.

Show evidence (2 references)

PMID:15469975 SUPPORT INDIRECT PRIMARY RESULT Model Organism

"In vivo imaging of muscle Ca2+ transients revealed that cytosolic Ca2+ decay was significantly slower in acc muscle."

Direct calcium imaging in an atp2a1 zebrafish mutant supports impaired post-contraction clearance.

PMID:25614869 SUPPORT INDIRECT BACKGROUND Human Clinical

"The “off” signal, that induces muscle relaxation, is the pumping of Ca2+ from the myoplasm back into the SR"

Physiological background explains how impaired reuptake delays relaxation.

Electrically Silent Muscle Contracture

Contractures after voluntary contraction can persist without myotonic discharges on EMG. This describes the abnormal contraction episode, not absence of all physiological motor-unit activity. Silent contractures are elicited in a subset of tested patients and are not specific to Brody disease alone.

relaxation of muscle GO:0090075 ↓ DECREASED

Downstream

Exercise-induced muscle stiffness Sustained contraction is experienced as exertional stiffness.

Delayed muscle relaxation Persistent contraction produces the examination sign.

Rhabdomyolysis Severe sustained contraction can be associated with muscle breakdown, especially during exertion or perioperative events.

Difficulty running Sustained contraction limits coordinated movement and produces this functional symptom.

Gait disturbance Failure to relax muscles disrupts the walking and running pattern.

Muscle cramps Painful sustained contractures are experienced as muscle cramps at rest or during exercise.

Show evidence (2 references)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"EMG can reveal silent contractures defined as prolonged involuntary muscle contractions (following voluntary phasic contractions) without electrical activity detected on EMG"

Defines the contraction readout without myotonic electrical discharges.

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"None of the patients had myotonic discharges on EMG (n = 30). Silent contractures were present in 18/28 patients"

The cohort distinguishes a consistent negative electrical finding from an incompletely detected positive contracture.

Selective Type II Fibre Involvement

SERCA1 expression in fast-twitch fibres accounts for preferential involvement of type II skeletal muscle and vulnerability during rapid repetitive activity. Biopsy often shows type II atrophy with internal nuclei and fibre-size variability; occasional type I changes mean that slow fibres are not absolutely spared morphologically.

type II muscle cell CL:0002212

Downstream

Type 2 muscle fiber atrophy Preferential fast-fibre involvement is reflected in biopsy morphology.

Delayed eyelid relaxation The high fast-fibre content of orbicularis oculi is a proposed explanation for eyelid involvement.

Show evidence (2 references)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Atrophy of type II fibres was seen in 76% (13/17) of patients, of which two also demonstrated type I atrophy."

Biopsy findings establish predominant, but not exclusive, type II involvement.

PMID:32040565 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"Delayed muscle relaxation occurred especially after explosive, short and repetitive contractions, which is explained by the selective type II muscle fibre involvement."

The clinical pattern is consistent with the physiological distribution of SERCA1.

Compensatory Calcium Extrusion and Handling

Mechanism confidence: Hypothetical

Compensatory calcium handling is a candidate explanation for relatively preserved function despite severe SERCA1 loss. Increased PMCA protein and altered mitochondrial-marker distribution occur in a bovine case; ectopic SERCA2 expression occurs in one human biopsy. These observations do not establish the magnitude of calcium flux, prove that adaptation causes the mild course, or require the mechanisms to be mutually exclusive.

calcium ion transmembrane transport GO:0070588 ↑ INCREASED

Animal models

Dutch Improved Red and White calf with ATP2A1 R559C Cattle partially recapitulates Provides expression-level clues to compensatory calcium handling, not direct proof of increased extrusion flux.

Atp2a1-null mouse Mouse fails to recapitulate The assayed compensatory changes were not detected in this lethal neonatal model.

Show evidence (2 references)

PMID:26482047 SUPPORT INDIRECT PRIMARY RESULT Model Organism

One affected calf shows altered protein-marker expression; increased calcium flux and a causal rescue of severity were not directly demonstrated.

PMID:25614869 SUPPORT INDIRECT PRIMARY RESULT Human Clinical

In one index-patient biopsy, increased SERCA2 abundance and ectopic staining support a candidate adaptation; restoration of flux was inferred.

✶

Histopathology

Type II fibre atrophy and fibre-size variability

Mild myopathic changes commonly include preferential type II atrophy, fibre-size variability and increased internal nuclei. Findings are supportive and nonspecific; type I changes also occur. Clinical bulk can remain normal.

Show evidence (1 reference)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Systematic re-evaluation of the biopsy reports showed fibre type II atrophy, increased fibre size variability, and an increased number of internal nuclei."

Summarizes the systematic biopsy review.

Sarcoplasmic reticulum remodeling

One patient biopsy showed dilated lateral cisternae and proliferating tubular SR elements. This ultrastructural observation should not be used alone as evidence for decreased protein expression.

Show evidence (1 reference)

PMID:20142766 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Ultrastructural examination revealed dilatation of lateral cisternae and proliferation of tubular elements of the sarcoplasmic reticulum."

Direct human ultrastructural result.

Usually limited myonecrosis

Discrete necrosis occurred in one reviewed biopsy, with degeneration in two additional specimens. Extensive necrosis is not the typical baseline pattern, but acute rhabdomyolysis and more severe bovine muscle injury are documented.

Show evidence (1 reference)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Discrete necrosis was found in only one biopsy (Patient L18). The same biopsy also showed sparse regeneration, and two other biopsies showed degeneration"

Qualifies the usual absence rather than claiming muscle injury never occurs.

⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.

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Phenotypes

Metabolism 1

Elevated circulating creatine kinase activity FREQUENT HP:0003236

Show evidence (1 reference)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Creatine kinase was considered normal in 12/24 patients and slightly to moderately elevated in 12/24 patients"

Cohort denominator supports the frequency band and distinguishes resting values from acute muscle injury.

Musculoskeletal 11

Exercise-induced muscle stiffness VERY_FREQUENT HP:0008967

Onset: CHILDHOOD

Show evidence (3 references)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Exercise-induced muscle stiffness was reported in all patients"

Core finding in this selected 40-patient cohort.

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Almost all patients reported onset of symptoms in childhood (38/40)."

Supports typical childhood onset without excluding later onset.

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"The majority of patients mentioned an increase of symptoms upon exposure to cold temperatures (25/36)."

Records an environmental symptom modifier, not a cause of disease.

Rhabdomyolysis HP:0003201

Sequelae: Elevated circulating creatine kinase activity

Show evidence (3 references)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"He also experienced two episodes of rhabdomyolysis following exercise at ages 19 and 22 with creatine kinase levels up to 221 600 IU/l and 100 000 IU/l, respectively."

Full-text recurrent exertional injury in one patient.

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"One other patient (Patient N15) experienced an episode of exertional rhabdomyolysis."

A second patient establishes that the finding predates the recent report.

PMID:41926432 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Patient is a 19-year-old woman presenting with exercise-induced rhabdomyolysis."

Recent clinical case; the abstract does not provide the complete biallelic genotype.

Proximal muscle weakness OCCASIONAL HP:0003701

Show evidence (2 references)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"mild proximal muscle weakness in 3/35 patients"

Objective weakness is reported and should not be encoded as universally absent.

PMID:38125752 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"mild progressive proximal muscle weakness in the lower extremities"

Individual adult observation in a reported homozygous ATP2A1 case; not a population prognosis.

Percussion myotonia OCCASIONAL HP:0010548

Show evidence (1 reference)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Percussion myotonia was reported in 4/34 patients"

Directly contradicts a blanket exclusion of the clinical sign.

Muscle cramps FREQUENT Muscle spasm HP:0003394

Show evidence (1 reference)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Patients variably reported muscle cramps (defined as involuntary and painful sustained muscle contractures) at rest or during exercise (18/34)."

Reports the authors’ definition and combined rest/exercise denominator.

Skeletal muscle hypertrophy OCCASIONAL HP:0003712

Show evidence (1 reference)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Several patients were described as having an athletic appearance (20/30) and/or as having hypertrophic muscles (10/34)."

Uses the hypertrophy-specific denominator rather than applying the athletic-build frequency to muscle hypertrophy.

Difficulty running HP:0009046

Show evidence (1 reference)

PMID:38373275 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"All presented with exercise-induced delayed relaxation, reported as difficulty running and performing sports."

Core functional presentation in the pediatric cohort.

Frequent falls HP:0002359

Show evidence (1 reference)

PMID:37332993 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Both the probands display difficulty in climbing stairs and running, frequent falls, delayed muscle relaxation after exertion."

Case-level clinical support from two genetically investigated siblings.

Type 2 muscle fiber atrophy FREQUENT HP:0003554

Show evidence (1 reference)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Atrophy of type II fibres was seen in 76% (13/17) of patients, of which two also demonstrated type I atrophy."

Biopsy-selected cohort proportion; not generalized clinical muscle wasting.

Increased variability in muscle fiber diameter VERY_FREQUENT HP:0003557

Show evidence (1 reference)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Variability of muscle fibre size was markedly increased in 92% (11/12) of samples."

Specimen-based denominator supports the morphology finding.

Centrally nucleated skeletal muscle fibers HP:0003687

Show evidence (1 reference)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Nuclear centralization and nuclear clumping was sporadically seen in the second biopsy"

Direct support for the more specific morphology; avoids conflating all internal with central nuclei.

Nervous System 1

Gait disturbance HP:0001288

Show evidence (1 reference)

PMID:38373275 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"However, the walking and running patterns were abnormal."

Direct pediatric observation; not evidence of a primary central nervous system disorder.

Constitutional 1

Myalgia FREQUENT HP:0003326

Show evidence (2 references)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Myalgia was commonly reported (20/34) and usually had a generalized distribution."

Direct cohort result supports the frequency band.

PMID:37332993 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"two siblings presenting childhood-onset exercise-induced muscle stiffness without pain"

Documents that pain is not obligatory.

Other 5

Delayed muscle relaxation FREQUENT

Show evidence (1 reference)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Delayed relaxation following repetitive contractions or sustained contraction was observed in 22/33 and 27/34 patients, respectively."

Separate tested denominators support the two examination maneuvers.

Malignant hyperthermia-like episodes

Left without a malignant-hyperthermia ontology binding because the cited study does not establish that diagnosis for all reported events. Perioperative precautions remain appropriate.

Show evidence (2 references)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Four patients had episodes resembling malignant hyperthermia."

The authors use a resemblance qualifier, not confirmation of four classic MH crises.

PMID:32040565 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"The MH-like episodes in Brody disease were most likely anaesthesia- or exercise-induced rhabdomyolysis without signs of hypermetabolism"

The full discussion qualifies the abstract and distinguishes these reactions from classic hypermetabolic MH.

Generally preserved muscle strength and bulk

Show evidence (2 references)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Physical examination revealed no muscle atrophy in any of the patients (0/33) and mild proximal muscle weakness in 3/35 patients"

Separates absent clinical atrophy from a documented minority with weakness.

PMID:38373275 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Muscle strength and mass was normal, and several children even had an athletic appearance."

The pediatric series supports preserved strength and mass in its nine children.

Absence of myotonic discharges

Show evidence (1 reference)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"None of the patients had myotonic discharges on EMG (n = 30). Silent contractures were present in 18/28 patients"

Distinguishes absent myotonic discharges from incompletely elicited contractures.

Delayed eyelid relaxation FREQUENT

Show evidence (2 references)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"The muscle groups predominantly affected were lower limbs (38/38), upper limbs (33/38), and eyelids (24/38)."

Reported eyelid involvement in 24/38 cohort patients.

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Delayed relaxation specifically of the eyelids was seen after repetitive eyelid-closure in 19/31 patients and after sustained forceful eyelid-closure in 17/29 patients."

Separate examination maneuvers and tested denominators; both support delayed eyelid relaxation.

🧬

Genetic Associations

ATP2A1

Gene: ATP2A1 hgnc:811 relationship_type: CAUSATIVE

Autosomal recessive

Show evidence (4 references)

PMID:8841193 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"We have now associated Brody disease with the autosomal recessive inheritance of three ATP2A1 mutations in two families"

Founding human genetic evidence establishes recessive ATP2A1 causation.

PMID:10914677 SUPPORT DIRECT PRIMARY RESULT In Vitro

"The Pro789 to Leu mutant was readily expressed in HEK-293 cells, but it demonstrated an almost complete loss of Ca2+ transport activity because of reduced Ca2+ affinity."

The human disease-associated substitution impairs intrinsic transport despite expression in a heterologous assay.

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"DNA alterations at the ATP2A1 gene locus represent the whole spectrum of mutation types: whole gene deletion, single exon deletion, splice site mutations, small exonic frameshift deletions or insertions, missense substitutions, and in-frame small deletions"

The patient series establishes the observed variant spectrum.

+ 1 more reference

💊

Medical Actions

Trigger-Free Anaesthesia and Perioperative Monitoring

Action: Therapeutic Procedure NCIT:C49236

Platform: Other

Plan anesthesia with specialist precautions because of reported anesthesia-associated rigidity, rhabdomyolysis and MH-like reactions. The cohort recommends avoiding succinylcholine and inhalational agents and monitoring vital signs including core temperature. This management recommendation does not establish a quantified risk of classic malignant hyperthermia or prove a reduction in mortality.

Show evidence (1 reference)

PMID:32040565 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"avoid administration of succinylcholine and inhalational agents, and monitor vital functions including core temperature"

The cohort recommends perioperative precautions despite uncertainty about classic MH susceptibility.

Symptomatic Pharmacotherapy

Action: Pharmacotherapy NCIT:C15986

Platform: Small molecule

Symptomatic drugs often provide limited benefit or unacceptable adverse effects. In the 2020 cohort, mexiletine improved symptoms in one of two exposed patients but was stopped because of side effects; carbamazepine, ibuprofen, nifedipine and other tried agents did not provide sustained benefit. Drug selection and monitoring require individual clinical assessment.

Show evidence (2 references)

PMID:32040565 REFUTE DIRECT PRIMARY RESULT Human Clinical

"Symptomatic treatment was mostly ineffective or produced unacceptable side effects."

Overall cohort experience limits claims of general symptomatic efficacy.

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Mexiletine improved symptoms in one patient but was similarly stopped because of side effects."

Captures a transient individual response and its tolerability limit.

Dantrolene

Action: Pharmacotherapy NCIT:C15986

Agent: dantrolene CHEBI:4317

Platform: Small molecule

Dantrolene reduces skeletal-muscle calcium release and is used off label for symptoms in selected patients. Five exposed patients in the 2020 series had no reported benefit, whereas a 2026 single case reported marked improvement. These uncontrolled observations indicate variable response, not established efficacy or an explained genotype-specific difference.

Mechanism Target:

MODULATES Prolonged Cytosolic Calcium Elevation — Reducing calcium release may lower the load that deficient SERCA1 cannot promptly clear.

Show evidence (1 reference)

PMID:32040565 SUPPORT INDIRECT REVIEW SYNTHESIS Human Clinical

"Verapamil and dantrolene, drugs that limit the Ca2+ release from the sarcoplasmic reticulum"

Mechanistic rationale discussed by the cohort authors, not direct calcium measurements in the responding case.

Show evidence (2 references)

PMID:41926432 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Treatment with dantrolene sodium resulted in marked clinical improvement."

Single uncontrolled Brody-labeled clinical case; this supports an individual response, not established general efficacy.

PMID:32040565 REFUTE DIRECT PRIMARY RESULT Human Clinical

"dantrolene (n = 5) ... The other medications showed no effect"

The full treatment paragraph identifies dantrolene among agents without observed benefit, in contrast to verapamil and mexiletine.

Verapamil

Action: Pharmacotherapy NCIT:C15986

Agent: verapamil CHEBI:9948

Platform: Small molecule

In the 2020 retrospective series, three of nine exposed patients improved, but two stopped because of adverse effects. One patient received successful long-term treatment. This supports possible individualized symptomatic benefit rather than predictable efficacy.

Mechanism Target:

MODULATES Prolonged Cytosolic Calcium Elevation — The proposed symptomatic approach reduces calcium release rather than restoring SERCA1 expression.

Show evidence (1 reference)

PMID:32040565 SUPPORT INDIRECT REVIEW SYNTHESIS Human Clinical

"Verapamil and dantrolene, drugs that limit the Ca2+ release from the sarcoplasmic reticulum"

Mechanistic rationale for reducing cytosolic calcium burden.

Show evidence (2 references)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Verapamil improved symptoms in three patients but was stopped in two of them because of side effects."

Three of nine exposed patients reported benefit; only one continued successfully long term.

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"only 1 of 18 treated patients received long-term successful treatment (Patient N15; verapamil)."

Distinguishes long-term success from short-lived response across the treated cohort.

CFTR Correctors (Investigational)

Action: Pharmacotherapy NCIT:C15986

Agent: C17 CFTR corrector

Platform: Small molecule

C17, C4 and C9 increase abundance of selected bovine SERCA1 mutants in heterologous cells. Local C17 injections in two affected calves increased SR-associated SERCA1 and calcium-ATPase activity; whole-animal functional recovery and systemic safety were not established. C17 failed to improve key morphological and locomotor outcomes in the S766F accordion zebrafish model, which has a different molecular defect. Lumacaftor and tezacaftor were relatively ineffective in the tested cell assay. Human therapeutic benefit remains unproven.

Mechanism Target:

MODULATES Proteasomal Degradation of Misfolded SERCA1 — The strategy preserves abundance of selected unstable but catalytically competent pumps; its precise molecular mechanism is not fully established.

Show evidence (1 reference)

PMID:41206505 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"the incubation with CFTR correctors C17, C4 and C9, induced an increase in the expression level of SERCA1 mutant almost equivalent to that of MG132-treated cells"

Expression rescue in transfected cells; not proof of direct proteasome inhibition.

Show evidence (3 references)

PMID:41206505 SUPPORT INDIRECT PRIMARY RESULT Model Organism

"The functional assay indicated that SR-enriched membrane fraction obtained from C17 treated muscle fibers displayed in parallel an increase in maximal Ca2+-ATPase activity"

Biochemical improvement after local intramuscular treatment in two affected calves; not demonstrated systemic or clinical efficacy in humans.

PMID:39273176 REFUTE INDIRECT PRIMARY RESULT Model Organism

"the Tq206−/− embryos treated with C17 (orange color) did not exhibit any significant differences after treatment, neither in terms of body length (Figure 5A) or tail curvature angles (Figure 5B)."

The S766F homozygous zebrafish model did not show morphological rescue; locomotor rescue was also not significant.

PMID:41206505 REFUTE INDIRECT PRIMARY RESULT In Vitro

"Other tested CFTR correctors including VX809 ... VX661 ... and the molecule glafenine, were less effective or almost totally ineffective in rescuing R164H mutant SERCA1."

Approved cystic-fibrosis drugs cannot be assumed to reproduce the experimental C17 result.

Proteasome Inhibition (Experimental Proof of Mechanism)

Action: Pharmacotherapy NCIT:C15986

Agent: MG132 CHEBI:75142

Platform: Small molecule

MG132 restores mutant SERCA1 abundance and function in cellular and bovine muscle-explant experiments involving selected destabilized variants. This establishes a degradation mechanism and a rescue assay; there is no demonstrated clinical benefit or safe systemic regimen for Brody patients.

Mechanism Target:

INHIBITS Proteasomal Degradation of Misfolded SERCA1 — Blocking the proteasome prevents premature mutant-protein disposal.

Show evidence (1 reference)

PMID:25288803 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"The treatment with MG132, an inhibitor of ubiquitin proteasome system, rescues the expression level and membrane localization of the SERCA1 mutant in a heterologous cellular model."

Proof of mechanism for bovine R164H in cells; not a treatment recommendation for patients.

Show evidence (2 references)

PMID:25288803 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"The treatment with MG132, an inhibitor of ubiquitin proteasome system, rescues the expression level and membrane localization of the SERCA1 mutant in a heterologous cellular model."

Proof of mechanism for bovine R164H in cells; not a treatment recommendation for patients.

PMID:36293223 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"incubation of G211V-transfected cells with proteasome inhibitor MG132 led to a significant increase in microsomal Ca2+ ATPase activity"

Biochemical rescue complements increased protein abundance.

Activity Pacing and Trigger Management

Action: Therapeutic Procedure NCIT:C49236

Platform: Behavioral / lifestyle

Adjust rapid repetitive activity to individual tolerance and use rest breaks to relieve stiffness. Cold exposure can worsen symptoms, so temperature and activity adjustments may help symptom avoidance. This is pragmatic supportive management; the cited evidence does not establish a standardized physical-therapy or warm-up protocol.

Show evidence (2 references)

PMID:25614869 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"Brody disease has a mild presentation when muscular activity is paced at tolerable levels, but becomes acute with rapid, repetitive exercise."

Clinical discussion supports pacing as a practical response to the exertional phenotype.

PMID:32040565 SUPPORT INDIRECT PRIMARY RESULT Human Clinical

"The majority of patients mentioned an increase of symptoms upon exposure to cold temperatures (25/36)."

Observed trigger provides an indirect rationale for temperature management.

Genetic Counselling

Action: Genetic Counseling NCIT:C15240

Platform: Behavioral / lifestyle

Discuss autosomal recessive inheritance, confirm the familial variants and their phase, and offer appropriate family testing. For two carrier parents, the usual recurrence risk is 25% per pregnancy. Identifying affected relatives also allows communication of perioperative precautions; heterozygous carrier status alone is not equivalent to the affected phenotype.

Show evidence (2 references)

PMID:37332993 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"The bi-allelic inheritance was verified by Sanger sequencing in the unaffected parents."

Family segregation provides direct evidence for recessive counseling.

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Heterozygous family members of patients (carriers) did not exhibit the Brody disease phenotype"

Observed carrier status supports distinguishing carriers from affected relatives; this was not systematically assessed.

🔬

Biochemical Markers

Sarcoplasmic reticulum calcium ATPase activity (DECREASED)

Reference Ranges

≥ 36.6 mU/mg (Study-specific frozen quadriceps samples from 28 healthy controls; optimized molybdate-Fe(II) phosphate assay)

Lower limit calculated as control mean minus two standard deviations; mU per mg total protein. Not a universal clinical cutoff. No upper reference limit was established. Patient samples included two quadriceps and two deltoid biopsies; age, sex, muscle site and other myopathies require further validation.

Show evidence (1 reference)

PMID:41938373 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"resulting in an overall lower limit of normal of 36.6 mU/mgP (mean – 2xSD)."

Source-defined one-sided lower reference limit, not an inferred interval from the patient mean.

Show evidence (2 references)

PMID:41938373 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Brody disease muscle samples (30.0 ± 4.2 mU/mg protein) compared to controls (86.7 ± 25.1 mU/mg protein)"

Quantitative values from the specified assay and small clinical sample.

PMID:41938373 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"with the measurement of compound SERCA activity there is no differentiation between SERCA1 and SERCA2 activity."

Explicit analytical specificity limit.

SERCA1 protein abundance (DECREASED)

Show evidence (2 references)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"All immunoblot analyses demonstrated absent or severely decreased amounts of SERCA protein."

Patient protein-abundance result.

PMID:41938373 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"western blots provide information on SERCA1 protein content but not on its function and vice versa for the SERCA activity assay."

Explains why abundance does not replace a functional assay.

🔬

Diagnosis

Clinical provocation and electromyography

Examine relaxation after repeated rapid contractions and sustained hand grip or eyelid closure. Absence of myotonic discharges with clinically evident delayed relaxation suggests Brody disease. Silent contractures may need active provocation and are not always elicited; normal routine EMG does not exclude the diagnosis.

Show evidence (1 reference)

PMID:32040565 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"when EMG shows no myotonic discharges in patients clinically suspected of having a myotonic disorder, provocation of possible silent contractures is recommended by performing rapid contractions during EMG."

Clinical testing recommendation from the cohort.

ATP2A1 sequencing with deletion analysis when indicated

Sequence ATP2A1 directly or use an appropriate myopathy panel/exome approach. Ensure exon and gene copy-number changes are assessed, particularly when clinical and functional evidence is convincing but only one pathogenic allele is found. The pediatric series recommends including ATP2A1 in congenital-myopathy, developmental/movement-disorder and muscle-channelopathy panels.

Show evidence (3 references)

PMID:32040565 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"we recommend direct sequencing of the ATP2A1 gene or next generation sequencing with a myopathy panel"

Recommended molecular confirmation.

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"This led to the discovery of an additional large-scale deletion of exon 9, confirming Brody disease as the diagnosis."

An unresolved second allele was found after further analysis prompted by biochemical deficiency.

PMID:38373275 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"We propose that ATP2A1 should be added to gene panels for congenital myopathies, developmental and movement disorders, and muscle channelopathies."

Expands pediatric diagnostic recognition without redefining Brody disease as a primary neurodevelopmental disorder.

Complementary SERCA activity and protein assays

Muscle calcium-ATPase measurement and SERCA1 western blot can support interpretation of uncertain ATP2A1 variants. The 2026 optimized assay provides laboratory-specific quantitative data. Reduced compound activity is not a stand-alone proof of variant pathogenicity or Brody disease because other myopathies and assay contributors can alter it.

Show evidence (2 references)

PMID:41938373 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"For ATP2A1 variants of uncertain significance, decreased SERCA activity can provide supportive evidence for the diagnosis of Brody disease"

Defines supportive clinical use rather than automatic reclassification.

PMID:41938373 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"it is possible that SERCA activity is also abnormal in other (calcium related) myopathies"

Disease-specificity limitation from the assay study.

SERCA1 immunohistochemistry limitations

Normal or near-normal immunostaining does not exclude reduced protein content or dysfunctional SERCA1. Western blot and functional assessment can be abnormal when staining appears preserved.

Show evidence (2 references)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"SERCA1 staining revealed a severe reduction in six patients (6/12) and was normal in the other patients (6/12)"

Observed false reassurance from staining alone.

PMID:23911890 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"SERCA1 reactivity was observed in type 2 muscle fibers of patients with and without ATP2A1 mutations and staining intensity was similar in patients and controls."

Independent study supports limited discriminatory value.

📈

Progression

Long-term course

Most patients have a relatively stable course, but strict lifelong nonprogression is not established. In the international cohort, 27 patients had follow-up averaging 9.3 years and three had more limited information. Seven of these 30 reported increased symptoms, while physicians observed no new weakness or atrophy. Retrospective ascertainment and the relatively young cohort limit conclusions about late adulthood.

Show evidence (2 references)

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Of these 30 patients, seven patients reported that symptoms had increased (23%)."

The denominator combines 27 patients with follow-up and three with limited progression information.

PMID:32040565 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"No development of weakness or atrophy was seen by physicians during follow-up physical examination."

Reported symptom progression was not accompanied by newly observed weakness or atrophy in this cohort.

📊

Prevalence

Worldwide

Unknown Ultra Rare

Exact prevalence is unknown. Published cohort sizes and literature counts are ascertainment summaries and should not be divided by the world population or treated as a measured incidence.

Show evidence (1 reference)

url:https://medlineplus.gov/genetics/condition/brody-myopathy/ SUPPORT DIRECT REVIEW SYNTHESIS Other

"Brody myopathy is a rare condition, although its exact prevalence is unknown."

Authoritative clinical summary does not supply a measured prevalence estimate.

🔀

Differential Diagnoses

Conditions with similar clinical presentations that must be differentiated from Brody Myopathy:

Brody syndrome without identified ATP2A1 variants

Overlapping Features Historically describes delayed relaxation and reduced SERCA activity without identified ATP2A1 variants. The 17-patient study found greater myalgia and daily-life impact than in gene-confirmed disease. This is not a genetically resolved subtype, and incomplete genetic testing or another cause of reduced activity must be considered.

Show evidence (2 references)

PMID:22704959 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"a distinction between Brody disease (with ATP2A1 mutations) and Brody syndrome (without ATP2A1 mutations) was proposed."

Defines the scope boundary.

PMID:22704959 SUPPORT DIRECT PRIMARY RESULT Human Clinical

"Patients with Brody syndrome more often report myalgia and experience a considerable impact on daily life."

Clinical comparison in the historical syndrome study.

Myotonia congenita and paramyotonia congenita

Overlapping Features These channelopathies commonly produce myotonic discharges, unlike the typical Brody pattern of electrically silent contractures. Clinical percussion myotonia alone does not settle the distinction.

Show evidence (1 reference)

PMID:32040565 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"myotonic disorders will typically demonstrate myotonic discharges at myography that are not seen in Brody disease"

Comparative diagnostic guidance; the qualifier typically avoids a universal statement about every myotonic presentation.

McArdle disease

Overlapping Features Can also produce silent contractures. A second-wind phenomenon, persistently high creatine kinase and recurrent exercise-associated rhabdomyolysis favor McArdle disease, although rhabdomyolysis can also occur in Brody disease.

Show evidence (2 references)

PMID:32040565 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"Silent contractures can also be found in McArdle disease (glycogen storage disease type V)."

Electrical silence is not uniquely diagnostic of Brody disease.

PMID:32040565 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"McArdle disease typically presents with a second wind phenomenon, permanently high creatine kinase levels and episodes of rhabdomyolysis"

The broader phenotype helps distinguish the disorders.

Rippling muscle disease

Overlapping Features Mechanically induced visible rippling or muscle mounding can also be electrically silent. Hereditary and immune-mediated forms differ from the ATP2A1-related relaxation defect.

Show evidence (1 reference)

PMID:42124386 SUPPORT DIRECT REVIEW SYNTHESIS Human Clinical

"Rippling muscle disease (RMD) and Brody disease are extremely rare nonprogressive myopathies associated with electrical silence on needle EMG during muscle stiffness and delayed muscle relaxation"

The clinical review supports overlap in electrical silence; disease mechanisms and provocation patterns differ.

🧫

Experimental Models

HEK293 expression of human SERCA1 P789L and R819C CELL_LINE

P789L was readily expressed but lost most calcium transport because of reduced calcium affinity. R819C retained near-normal transport and was not supported as causative in the reported family. This assay separates expression from function; heterologous cells do not reproduce mature fast-twitch muscle physiology.

Organism

Homo sapiens NCBITaxon:9606

Cell source

Heterologous HEK293 cells expressing human wild-type or mutant SERCA1

Publication

PMID:10914677

Pathograph links

Intrinsic SERCA1 Calcium-Transport Defect perturbs fidelity: moderate Tests intrinsic transport impairment separately from protein abundance.

Show evidence (1 reference)

PMID:10914677 SUPPORT DIRECT PRIMARY RESULT In Vitro

"The Pro789 to Leu mutant was readily expressed in HEK-293 cells, but it demonstrated an almost complete loss of Ca2+ transport activity because of reduced Ca2+ affinity."

Direct functional assay of a human disease-associated allele.

Heterologous bovine SERCA1 instability and corrector assays CELL_LINE

Transfected-cell assays measure mutant abundance, ER localization, ubiquitination, calcium transients and microsomal ATPase activity. G211V reduces abundance whereas G286V is largely benign. Proteasome inhibition and selected CFTR correctors rescue unstable variants. Host-cell species does not make these human pathogenic-variant experiments.

Organism

Homo sapiens NCBITaxon:9606

Cell source

HEK293 or HeLa host cells expressing rabbit SERCA1 with R164H or bovine SERCA1 with G211V/G286V substitutions

Publication

PMID:36293223

Pathograph links

Proteasomal Degradation of Misfolded SERCA1 perturbs fidelity: moderate Tests ubiquitination and protein rescue after proteasome inhibition.

Show evidence (1 reference)

PMID:36293223 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"Inhibition of the UPS with MG132 led to an increase in the recovery of the polyubiquitinated G211V mutant"

Direct biochemical evidence for altered protein disposal in the transfected-cell system.

Reduced SERCA1 Density at the Sarcoplasmic Reticulum Membrane perturbs fidelity: moderate Corrector screening measures restoration of mutant protein abundance.

Show evidence (1 reference)

PMID:41206505 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"the incubation with CFTR correctors C17, C4 and C9, induced an increase in the expression level of SERCA1 mutant almost equivalent to that of MG132-treated cells"

Expression-level rescue does not alone establish clinical efficacy.

Bovine pseudomyotonia muscle explants OTHER

Muscle explants preserve differentiated diseased tissue for MG132 or corrector exposure. C17 and C4 increased mutant SERCA1 in SR-enriched fractions. Ex vivo response avoids whole-animal pharmacokinetics and therefore cannot establish systemic safety or functional benefit.

Organism

Bos taurus NCBITaxon:9913

Cell source

Fresh adult skeletal-muscle fibre bundles from affected cattle

Publication

PMID:41206505

Pathograph links

Reduced SERCA1 Density at the Sarcoplasmic Reticulum Membrane perturbs fidelity: moderate Tests pharmacological restoration of protein abundance in diseased muscle tissue.

Show evidence (1 reference)

PMID:41206505 SUPPORT INDIRECT PRIMARY RESULT In Vitro

"the treatment with C17 or C4 correctors efficiently increased SERCA1 mutant expression"

Explant immunoblot readout supports protein rescue.

Normal human primary muscle cultures for SERCA1 isoform characterization PRIMARY_CELL_CULTURE

Normal human cultured fibres predominantly express the neonatal SERCA1b isoform. This is an assay-development comparator rather than a demonstrated patient-derived Brody model, and isoform maturation must be considered when modeling adult SERCA1a disease.

Organism

Homo sapiens NCBITaxon:9606

Cell source

Primary cultures of normal human muscle; infant muscle examined for comparison

Publication

PMID:23911890

Show evidence (1 reference)

PMID:23911890 SUPPORT DIRECT PRIMARY RESULT In Vitro

"We found that SERCA1b, the SERCA1 neonatal form, is the main protein isoform expressed in cultured human muscle fibers and infant muscle."

Direct isoform result; the cultured cells were from normal human muscle.

🐁

Animal Models

Bovine congenital pseudomyotonia: Chianina and Romagnola ATP2A1 variants

Naturally occurring recessive disease produces exercise-induced stiffness, delayed relaxation and reduced SERCA1 abundance/activity. Functional separation of the Romagnola cis variants identifies G211V as pathogenic and G286V as largely benign. Local C17 treatment in two compound-heterozygous calves improved muscle biochemical endpoints, but systemic clinical efficacy was not established.

Species

Cattle

Genotype

R164H homozygosity; G211V/G286V cis allele homozygosity or compound heterozygosity with R164H

Publication

PMID:18786632

Pathograph links

Reduced SERCA1 Density at the Sarcoplasmic Reticulum Membrane partially recapitulates fidelity: moderate Models low SERCA1 abundance in skeletal muscle, with variant- and species-specific limits.

Show evidence (1 reference)

PMID:23046865 SUPPORT DIRECT PRIMARY RESULT Model Organism

"the amount of SERCA1 protein was decreased in the pathological samples with respect to control samples"

Whole-animal disease specimens show reduced abundance; this is not direct evidence of the same molecular route in every human variant.

Impaired Calcium Reuptake into the Sarcoplasmic Reticulum partially recapitulates fidelity: moderate Reduced calcium-ATPase activity in affected muscle models loss of reuptake capacity.

Show evidence (1 reference)

PMID:18786632 SUPPORT DIRECT PRIMARY RESULT Model Organism

"SERCA1 activity in affected animals was decreased by about 70%"

Founding Chianina study provides a functional muscle readout.

The 2012 abstract contains inconsistent amino-acid nomenclature; R164H and the distinction between G211V and G286V follow the corrected body text and the 2022 functional study. Degeneration can be more marked than in typical human biopsies.

Dutch Improved Red and White calf with ATP2A1 R559C

A naturally affected calf had exercise-induced stiffness and low SERCA1 activity. The same variant is associated with a more severe respiratory course in Belgian Blue cattle, indicating context-dependent expression. Increased PMCA and broadly distributed mitochondrial markers were observed without SERCA2 compensation.

Species

Cattle

Genotype

ATP2A1 p.Arg559Cys

Publication

PMID:20547455

Pathograph links

Compensatory Calcium Extrusion and Handling partially recapitulates fidelity: low Provides expression-level clues to compensatory calcium handling, not direct proof of increased extrusion flux.

Show evidence (1 reference)

PMID:26482047 SUPPORT DIRECT PRIMARY RESULT Model Organism

"an increased expression of sarcolemmal calcium extrusion pump"

Protein expression supports the candidate adaptation; no selective intervention establishes causal rescue.

accordion zebrafish, including atp2a1 tq206 S766F

Mutants show prolonged calcium transients and simultaneous bilateral trunk contraction. The tq206 S766F homozygote has severe larval abnormalities and early lethality, unlike the usually mild human course. C17 did not significantly rescue key morphological or locomotor endpoints in the 2024 experiment. Heterozygotes had largely preserved larval locomotion, although adult histology showed abnormalities.

Species

Zebrafish

Genotype

atp2a1 accordion alleles; tq206 S766F homozygotes and heterozygotes

Publication

PMID:15469975

Pathograph links

Impaired Calcium Reuptake into the Sarcoplasmic Reticulum partially recapitulates fidelity: moderate Recapitulates impaired calcium clearance after excitation, with species-specific behavioral and developmental readouts.

Show evidence (1 reference)

PMID:15469975 SUPPORT DIRECT PRIMARY RESULT Model Organism

"In vivo imaging of muscle Ca2+ transients revealed that cytosolic Ca2+ decay was significantly slower in acc muscle."

Direct in-vivo calcium-transient measurement.

Intrinsic SERCA1 Calcium-Transport Defect partially recapitulates fidelity: moderate S766F is a useful contrast to unstable, activity-retaining mutants; preserved expression and lack of corrector response are consistent with a functional defect.

Show evidence (1 reference)

PMID:39273176 SUPPORT DIRECT PRIMARY RESULT Model Organism

"Administration of the CFTR C17 corrector to Tq206−/− siblings exhibited no difference or improvement in morphological traits and swimming performance."

Negative rescue in the S766F model constrains the therapeutic generalization.

The 2024 study inferred impaired intrinsic S766F function from phenotype, expression and structural context; it did not directly establish the same calcium-affinity defect measured for human P789L. Embryonic/larval severity and early death limit modeling of human natural history.

Atp2a1-null mouse

Constitutive SERCA1 loss produces marked reduction in calcium transport, neonatal diaphragm dysfunction and death shortly after birth. The model captures severe loss of pump function but not the usually survivable human course. Diaphragm fibre composition, species-specific adaptation and residual allele activity may contribute to the mismatch.

Species

Mouse

Genotype

Atp2a1 homozygous null

Publication

PMID:12556521

Pathograph links

Impaired Calcium Reuptake into the Sarcoplasmic Reticulum partially recapitulates fidelity: moderate Recapitulates deficient calcium transport in diaphragm and skeletal muscle despite a much more severe clinical outcome.

Show evidence (1 reference)

PMID:12556521 SUPPORT DIRECT PRIMARY RESULT Model Organism

"The V(max) of Ca(2+) transport activity in mutant diaphragm and skeletal muscle was reduced by 80% compared with wild-type muscle"

Direct functional consequence of the engineered null.

Compensatory Calcium Extrusion and Handling fails to recapitulate fidelity: low The assayed compensatory changes were not detected in this lethal neonatal model.

Limitations: Comparison is with proposed human adaptation, whose functional magnitude remains uncertain. Constitutive complete loss, neonatal respiratory demand and species-specific muscle composition all limit inference.

Show evidence (1 reference)

PMID:12556521 SUPPORT DIRECT PRIMARY RESULT Model Organism

"No compensatory responses were detected in analysis of mRNAs encoding other Ca(2+) handling proteins or of protein levels."

Negative expression-level result in newborn mice; it does not prove all possible compensatory flux is absent.

{ }

Source YAML

click to show

name: Brody Myopathy
creation_date: "2026-08-16T00:00:00Z"
description: >-
  Brody myopathy is an autosomal recessive skeletal-muscle relaxation disorder caused by biallelic pathogenic
  ATP2A1 variants. Deficient SERCA1 abundance or calcium-transport function impairs calcium reuptake into the
  sarcoplasmic reticulum, particularly in fast-twitch muscle fibres. Exercise-induced stiffness and delayed
  relaxation usually begin in childhood, often affecting limbs and eyelids. Myotonic discharges are generally
  absent despite clinically evident contractures. Strength and bulk are usually preserved, but mild weakness,
  percussion myotonia and limited symptom progression are reported. Rhabdomyolysis and anesthesia-associated
  contractures warrant perioperative precautions; classic malignant hyperthermia susceptibility is not established
  for every patient. Experimental protein-rescue strategies apply to selected functionally competent mutant
  pumps and have not established clinical efficacy in humans.
category: Mendelian
disease_term:
  preferred_term: Brody Myopathy
  term:
    id: MONDO:0010977
    label: Brody myopathy
synonyms:
- Brody disease
- SERCA1 deficiency
- ATP2A1-related myopathy
- Sarcoplasmic reticulum calcium ATPase deficiency
notes: >-
  This entry covers ATP2A1-related Brody disease. The historically defined Brody syndrome describes a similar
  clinical and biochemical phenotype without identified ATP2A1 variants and is retained as a differential diagnosis.
  Clinical proportions below describe selected cohorts with variable denominators, not population frequencies.
  The 2020 international cohort included 40 patients from 28 families, with retrospective follow-up in a subset;
  childhood presentations are further characterized in a 2024 series of nine children. No reproducible genotype–phenotype
  severity correlation or disease-modifying treatment is established.
pathophysiology:
- name: Biallelic ATP2A1 Loss of Function
  biological_scale: MOLECULAR
  description: Biallelic pathogenic variants reduce SERCA1 abundance, stability or intrinsic calcium-transport function. Truncating alleles, exon/gene deletions, splice changes, in-frame deletions and missense substitutions are reported. Mechanisms overlap and cannot be assigned solely from variant class; for example, a splice variant causes an in-frame exon skip.
  evidence:
  - &id008
    reference: PMID:8841193
    reference_title: "Mutations in the gene-encoding SERCA1, the fast-twitch skeletal muscle sarcoplasmic reticulum Ca2+ ATPase, are associated with Brody disease."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: We have now associated Brody disease with the autosomal recessive inheritance of three ATP2A1 mutations in two families
    explanation: Founding human genetic evidence establishes recessive ATP2A1 causation.
  - reference: PMID:37332993
    reference_title: "Case report: Clinical and molecular characterization of two siblings affected by Brody myopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: we observed the skipping of the whole Exon 4
    explanation: Blood RNA analysis supports the splice effect of c.324+1G>A; the resulting transcript preserves the reading frame.
  gene:
    preferred_term: ATP2A1
    term:
      id: hgnc:811
      label: ATP2A1
  molecular_functions:
  - preferred_term: SERCA1 calcium transport
    term:
      id: GO:0005388
      label: P-type calcium transporter activity
    modifier: DECREASED
  downstream:
  - target: Proteasomal Degradation of Misfolded SERCA1
    description: Selected missense variants increase proteasomal disposal of a catalytically competent pump.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - &id001
      reference: PMID:36293223
      reference_title: Differential Analysis of Gly211Val and Gly286Val Mutations Affecting Sarco(endo)plasmic Reticulum Ca(2+)-ATPase (SERCA1) in Congenital Pseudomyotonia Romagnola Cattle.
      supports: SUPPORT
      evidence_source: IN_VITRO
      directness: INDIRECT
      quote_role: PRIMARY_RESULT
      snippet: After blocking the proteasome using a proteasome inhibitor, we found that the G211V mutant accumulates in cells at levels comparable to those of WT SERCA1.
      explanation: Proteasome inhibition rescues abundance of a bovine disease allele; this is not evidence that every human missense allele follows this mechanism.
  - target: Reduced SERCA1 Density at the Sarcoplasmic Reticulum Membrane
    description: Loss of expression or stability lowers pump abundance in patient muscle.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - &id002
      reference: PMID:32040565
      reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: All immunoblot analyses demonstrated absent or severely decreased amounts of SERCA protein.
      explanation: Human muscle analyses support reduced protein abundance in the tested patients; abundance and intrinsic function are distinct.
  - target: Intrinsic SERCA1 Calcium-Transport Defect
    description: Some substitutions directly impair calcium affinity and transport.
    causal_link_type: DIRECT
    evidence:
    - &id003
      reference: PMID:10914677
      reference_title: The mutation of Pro789 to Leu reduces the activity of the fast-twitch skeletal muscle sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA1) and is associated with Brody disease.
      supports: SUPPORT
      evidence_source: IN_VITRO
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: The Pro789 to Leu mutant was readily expressed in HEK-293 cells, but it demonstrated an almost complete loss of Ca2+ transport activity because of reduced Ca2+ affinity.
      explanation: The human disease-associated substitution impairs intrinsic transport despite expression in a heterologous assay.
- name: Proteasomal Degradation of Misfolded SERCA1
  biological_scale: MOLECULAR
  description: Bovine R164H and G211V SERCA1 variants are prematurely ubiquitinated and degraded despite retaining catalytic activity. Mutant protein can reach ER/SR membranes; the evidence supports accelerated disposal, not an obligatory block before membrane insertion. The extent to which this route applies to individual human variants requires functional testing.
  evidence:
  - *id001
  - reference: PMID:36293223
    reference_title: Differential Analysis of Gly211Val and Gly286Val Mutations Affecting Sarco(endo)plasmic Reticulum Ca(2+)-ATPase (SERCA1) in Congenital Pseudomyotonia Romagnola Cattle.
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    quote_role: PRIMARY_RESULT
    snippet: Co-localization using anti calreticulin antibodies, a well-known ER marker, confirmed that SERCA1 mutants are correctly targeted to ER
    explanation: Microscopy argues against an absolute pre-membrane trafficking block.
  - reference: PMID:25288803
    reference_title: Inhibition of ubiquitin proteasome system rescues the defective sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA1) protein causing Chianina cattle pseudomyotonia.
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    quote_role: PRIMARY_RESULT
    snippet: the mutation generates a protein most likely corrupted in proper folding but not in catalytic activity
    explanation: R164H experiments distinguish loss of abundance from loss of enzymatic competence.
  biological_processes:
  - preferred_term: proteasome-mediated ubiquitin-dependent protein catabolic process
    term:
      id: GO:0043161
      label: proteasome-mediated ubiquitin-dependent protein catabolic process
    modifier: INCREASED
  downstream:
  - target: Reduced SERCA1 Density at the Sarcoplasmic Reticulum Membrane
    description: Accelerated degradation decreases steady-state membrane pump abundance.
    causal_link_type: DIRECT
    evidence:
    - *id001
- name: Reduced SERCA1 Density at the Sarcoplasmic Reticulum Membrane
  biological_scale: MOLECULAR
  description: Reduced or absent SERCA1 protein is a common biochemical finding in tested patient muscle. A normal immunohistochemical stain does not exclude this deficit, and normal abundance would not exclude an intrinsic catalytic defect. SERCA1 is the dominant calcium pump in type II skeletal muscle fibres.
  evidence:
  - *id002
  - reference: PMID:20142766
    reference_title: "Brody disease: insights into biochemical features of SERCA1 and identification of a novel mutation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Immunoblotting after high-resolution 2-dimensional gel electrophoresis showed a significant difference in the amount of SERCA1 protein between the patient and controls.
    explanation: Human muscle protein analysis complements the calcium-ATPase assay.
  cellular_components:
  - preferred_term: sarcoplasmic reticulum membrane
    term:
      id: GO:0033017
      label: sarcoplasmic reticulum membrane
  downstream:
  - target: Impaired Calcium Reuptake into the Sarcoplasmic Reticulum
    description: Fewer functional pumps reduce the capacity for calcium reuptake.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:32040565
      reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: Sarcoplasmic/endoplasmic reticulum Ca2+ ATPase (SERCA) activity was reduced and western blot analysis showed decreased or absent SERCA1 protein.
      explanation: Paired functional and protein findings in human muscle.
  - target: Selective Type II Fibre Involvement
    description: The fast-twitch distribution of SERCA1 helps explain preferential type II pathology.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - &id005
      reference: PMID:32040565
      reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: Atrophy of type II fibres was seen in 76% (13/17) of patients, of which two also demonstrated type I atrophy.
      explanation: Biopsy findings establish predominant, but not exclusive, type II involvement.
- name: Intrinsic SERCA1 Calcium-Transport Defect
  biological_scale: MOLECULAR
  description: The human p.Pro789Leu substitution markedly reduces calcium affinity and calcium transport in transfected HEK293 cells despite readily detectable expression. This route is distinct from premature degradation of an otherwise competent pump. Functional defects may coexist with reduced abundance in patient tissue.
  evidence:
  - *id003
  molecular_functions:
  - preferred_term: P-type calcium transporter activity
    term:
      id: GO:0005388
      label: P-type calcium transporter activity
    modifier: DECREASED
  downstream:
  - target: Impaired Calcium Reuptake into the Sarcoplasmic Reticulum
    description: Lower transport activity limits calcium reuptake even when mutant protein is present.
    causal_link_type: DIRECT
    evidence:
    - *id003
- name: Impaired Calcium Reuptake into the Sarcoplasmic Reticulum
  biological_scale: CELLULAR
  description: Impaired SERCA1-dependent transport slows return of contraction-associated calcium to the sarcoplasmic reticulum. Human muscle calcium-ATPase assays and mutant animal calcium imaging support this deficit. The assays do not establish normal calcium release or exclude all other secondary calcium-handling changes.
  evidence:
  - &id004
    reference: PMID:15469975
    reference_title: "accordion, a zebrafish behavioral mutant, has a muscle relaxation defect due to a mutation in the ATPase Ca2+ pump SERCA1."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    quote_role: PRIMARY_RESULT
    snippet: In vivo imaging of muscle Ca2+ transients revealed that cytosolic Ca2+ decay was significantly slower in acc muscle.
    explanation: Direct calcium imaging in an atp2a1 zebrafish mutant supports impaired post-contraction clearance.
  - reference: PMID:41938373
    reference_title: Sarco/endoplasmatic reticulum calcium ATPase activity in healthy muscle and Brody disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: We were able to provide new reference values and demonstrate marked decreased SERCA activity in Brody disease muscle samples
    explanation: An optimized compound calcium-ATPase assay found low activity in four genetically confirmed patients.
  biological_processes:
  - preferred_term: calcium ion import into sarcoplasmic reticulum
    term:
      id: GO:1990036
      label: calcium ion import into sarcoplasmic reticulum
    modifier: DECREASED
  downstream:
  - target: Prolonged Cytosolic Calcium Elevation
    description: Slower calcium removal prolongs the post-contraction cytosolic transient.
    causal_link_type: DIRECT
    evidence:
    - *id004
  - target: Compensatory Calcium Extrusion and Handling
    description: Alternative calcium-handling responses may compensate for the primary deficit; the contribution varies between models and patients.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - &id006
      reference: PMID:26482047
      reference_title: Fast-twitch skeletal muscle fiber adaptation to SERCA1 deficiency in a Dutch Improved Red and White calf pseudomyotonia case.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: INDIRECT
      quote_role: PRIMARY_RESULT
      snippet: pathological muscles are characterized by a broad distribution of mitochondrial markers in all fiber types, not related to intrinsic features of double muscle phenotype and by an increased expression of sarcolemmal calcium extrusion pump.
      explanation: One affected calf shows altered protein-marker expression; increased calcium flux and a causal rescue of severity were not directly demonstrated.
    - &id007
      reference: PMID:25614869
      reference_title: Exome analysis identifies Brody myopathy in a family diagnosed with malignant hyperthermia susceptibility.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      directness: INDIRECT
      quote_role: PRIMARY_RESULT
      snippet: Analyses of affected muscles showed the absence of SERCA1, but SERCA2 upregulation in slow and fast myofibers, suggesting a compensatory mechanism that partially restores the diminished Ca(2+) transport in Brody myopathy.
      explanation: In one index-patient biopsy, increased SERCA2 abundance and ectopic staining support a candidate adaptation; restoration of flux was inferred.
    hypothesis_groups:
    - pmca_extrusion_compensation
    - serca2_isoform_compensation
- name: Prolonged Cytosolic Calcium Elevation
  biological_scale: CELLULAR
  description: Prolonged cytosolic calcium elevation sustains activation of the contractile machinery after the electrical stimulus has ended. Calcium-transient prolongation is directly observed in mutant zebrafish; this supports the human relaxation mechanism without proving that every clinical complication has the same immediate cause.
  evidence:
  - *id004
  - reference: PMID:25614869
    reference_title: Exome analysis identifies Brody myopathy in a family diagnosed with malignant hyperthermia susceptibility.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    quote_role: BACKGROUND
    snippet: The “off” signal, that induces muscle relaxation, is the pumping of Ca2+ from the myoplasm back into the SR
    explanation: Physiological background explains how impaired reuptake delays relaxation.
  biological_processes:
  - preferred_term: intracellular calcium ion homeostasis
    term:
      id: GO:0006874
      label: intracellular calcium ion homeostasis
    modifier: DYSREGULATED
  downstream:
  - target: Electrically Silent Muscle Contracture
    description: Delayed calcium clearance prolongs muscle contraction after excitation.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:15581877
      reference_title: A mutation in serca underlies motility dysfunction in accordion zebrafish.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: INDIRECT
      quote_role: PRIMARY_RESULT
      snippet: imaging of skeletal muscle of larval acc reveals greatly prolonged calcium transients and associated contractions in response to depolarization.
      explanation: Paired calcium and contraction readouts support the causal connection.
- name: Electrically Silent Muscle Contracture
  biological_scale: TISSUE
  description: Contractures after voluntary contraction can persist without myotonic discharges on EMG. This describes the abnormal contraction episode, not absence of all physiological motor-unit activity. Silent contractures are elicited in a subset of tested patients and are not specific to Brody disease alone.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: EMG can reveal silent contractures defined as prolonged involuntary muscle contractions (following voluntary phasic contractions) without electrical activity detected on EMG
    explanation: Defines the contraction readout without myotonic electrical discharges.
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: None of the patients had myotonic discharges on EMG (n = 30). Silent contractures were present in 18/28 patients
    explanation: The cohort distinguishes a consistent negative electrical finding from an incompletely detected positive contracture.
  biological_processes:
  - preferred_term: relaxation of muscle
    term:
      id: GO:0090075
      label: relaxation of muscle
    modifier: DECREASED
  downstream:
  - target: Exercise-induced muscle stiffness
    description: Sustained contraction is experienced as exertional stiffness.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:32040565
      reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: Exercise-induced muscle stiffness was reported in all patients
      explanation: Core clinical manifestation in the 40-patient cohort.
  - target: Delayed muscle relaxation
    description: Persistent contraction produces the examination sign.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:32040565
      reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: The key finding at physical examination was delayed relaxation after repetitive contractions.
      explanation: Characteristic clinical relaxation defect.
  - target: Rhabdomyolysis
    description: Severe sustained contraction can be associated with muscle breakdown, especially during exertion or perioperative events.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:32040565
      reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: He also experienced two episodes of rhabdomyolysis following exercise
      explanation: The cohort documents exercise-associated muscle injury; the exact intermediates are not established.
  - target: Difficulty running
    description: Sustained contraction limits coordinated movement and produces this functional symptom.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:38373275
      reference_title: "Brody Disease, an Early-Onset Myopathy With Delayed Relaxation and Abnormal Gait: A Case Series of 9 Children."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: All presented with exercise-induced delayed relaxation, reported as difficulty running and performing sports.
      explanation: Core functional presentation in the pediatric cohort.
  - target: Gait disturbance
    description: Failure to relax muscles disrupts the walking and running pattern.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:38373275
      reference_title: "Brody Disease, an Early-Onset Myopathy With Delayed Relaxation and Abnormal Gait: A Case Series of 9 Children."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: However, the walking and running patterns were abnormal.
      explanation: Direct pediatric observation; not evidence of a primary central nervous system disorder.
  - target: Muscle cramps
    description: Painful sustained contractures are experienced as muscle cramps at rest or during exercise.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:32040565
      reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: Patients variably reported muscle cramps (defined as involuntary and painful sustained muscle contractures) at rest or during exercise (18/34).
      explanation: Reports the authors’ definition and combined rest/exercise denominator.
- name: Selective Type II Fibre Involvement
  biological_scale: TISSUE
  description: SERCA1 expression in fast-twitch fibres accounts for preferential involvement of type II skeletal muscle and vulnerability during rapid repetitive activity. Biopsy often shows type II atrophy with internal nuclei and fibre-size variability; occasional type I changes mean that slow fibres are not absolutely spared morphologically.
  evidence:
  - *id005
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
    snippet: Delayed muscle relaxation occurred especially after explosive, short and repetitive contractions, which is explained by the selective type II muscle fibre involvement.
    explanation: The clinical pattern is consistent with the physiological distribution of SERCA1.
  cell_types:
  - preferred_term: type II muscle cell
    term:
      id: CL:0002212
      label: type II muscle cell
  downstream:
  - target: Type 2 muscle fiber atrophy
    description: Preferential fast-fibre involvement is reflected in biopsy morphology.
    causal_link_type: DIRECT
    evidence:
    - *id005
  - target: Delayed eyelid relaxation
    description: The high fast-fibre content of orbicularis oculi is a proposed explanation for eyelid involvement.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:32040565
      reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      directness: INDIRECT
      quote_role: PRIMARY_RESULT
      snippet: Eyelid involvement is most likely the result of the high percentage of type II muscle fibres in orbicularis oculi muscle
      explanation: The cohort authors propose fibre-type composition as the reason for eyelid involvement; the mechanism was not experimentally isolated in patients.
- name: Compensatory Calcium Extrusion and Handling
  biological_scale: CELLULAR
  description: Compensatory calcium handling is a candidate explanation for relatively preserved function despite severe SERCA1 loss. Increased PMCA protein and altered mitochondrial-marker distribution occur in a bovine case; ectopic SERCA2 expression occurs in one human biopsy. These observations do not establish the magnitude of calcium flux, prove that adaptation causes the mild course, or require the mechanisms to be mutually exclusive.
  evidence:
  - *id006
  - *id007
  mechanism_confidence: HYPOTHETICAL
  biological_processes:
  - preferred_term: calcium ion transmembrane transport
    term:
      id: GO:0070588
      label: calcium ion transmembrane transport
    modifier: INCREASED
mechanistic_hypotheses:
- hypothesis_group_id: pmca_extrusion_compensation
  hypothesis_label: Alternative calcium extrusion contributes to compensation
  status: EMERGING
  description: Increased sarcolemmal calcium-pump expression and altered mitochondrial-marker distribution in one affected calf support alternative calcium handling as a candidate adaptation. Protein abundance does not directly measure flux or demonstrate rescue. This mechanism can coexist with SERCA2 adaptation.
  evidence:
  - *id006
  notes: Direct human functional confirmation remains lacking in the cited studies.
- hypothesis_group_id: serca2_isoform_compensation
  hypothesis_label: SERCA2 upregulation contributes to compensation in some patients
  status: EMERGING
  description: One human index-patient biopsy showed increased SERCA2 abundance and expression in fast as well as slow fibres. Most other biopsies did not show increased SERCA2. The evidence supports a possible patient-dependent response, not a universal mechanism or an independently refuted observation.
  evidence:
  - *id007
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: The presence of the SERCA2 isoform was determined by immunohistochemistry in eight biopsies, with normal expression in seven patients and increased expression in one patient
    explanation: The cohort includes previously published cases and limits universality; it is not an independent failure to reproduce every original observation.
  - reference: PMID:26482047
    reference_title: Fast-twitch skeletal muscle fiber adaptation to SERCA1 deficiency in a Dutch Improved Red and White calf pseudomyotonia case.
    supports: REFUTE
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    quote_role: PRIMARY_RESULT
    snippet: The reduced expression of SERCA1 is selective and not compensated by the SERCA2 isoform.
    explanation: The affected calf did not show SERCA2 compensation; this does not rule out human patient-specific adaptation.
phenotypes:
- name: Exercise-induced muscle stiffness
  category: Neuromuscular
  description: Reported in all 40 patients in the international cohort. Symptoms often begin during rapid or repetitive activity and affect lower limbs, upper limbs and eyelids. Cold worsened symptoms in 25/36 evaluated patients. Childhood onset is typical, but later onset and mild progression occur.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Exercise-induced muscle stiffness was reported in all patients
    explanation: Core finding in this selected 40-patient cohort.
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Almost all patients reported onset of symptoms in childhood (38/40).
    explanation: Supports typical childhood onset without excluding later onset.
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: The majority of patients mentioned an increase of symptoms upon exposure to cold temperatures (25/36).
    explanation: Records an environmental symptom modifier, not a cause of disease.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Exercise-induced muscle stiffness
    term:
      id: HP:0008967
      label: Exercise-induced muscle stiffness
    onset:
      onset_category: CHILDHOOD
      notes: 'Typical rather than universal: 38/40 cohort patients recalled childhood onset.'
- name: Delayed muscle relaxation
  category: Neuromuscular
  description: Delayed relaxation after repeated or sustained voluntary contractions is the characteristic examination sign. It can involve the eyelids as well as limb muscles. Clinical relaxation delay does not imply electrical myotonia, and a routine EMG may fail to elicit silent contractures.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Delayed relaxation following repetitive contractions or sustained contraction was observed in 22/33 and 27/34 patients, respectively.
    explanation: Separate tested denominators support the two examination maneuvers.
  frequency: FREQUENT
- name: Malignant hyperthermia-like episodes
  category: Anaesthetic
  description: The cohort abstract groups four patients under MH-like events, but the full text distinguishes two anesthesia-associated reactions, an exertional rhabdomyolysis case and unexplained hyperthermia. These observations do not establish a 10% risk of classic malignant hyperthermia or an anesthesia-event rate. Positive contracture tests can reflect abnormal calcium handling without proving classic MH susceptibility.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Four patients had episodes resembling malignant hyperthermia.
    explanation: The authors use a resemblance qualifier, not confirmation of four classic MH crises.
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
    snippet: The MH-like episodes in Brody disease were most likely anaesthesia- or exercise-induced rhabdomyolysis without signs of hypermetabolism
    explanation: The full discussion qualifies the abstract and distinguishes these reactions from classic hypermetabolic MH.
  notes: Left without a malignant-hyperthermia ontology binding because the cited study does not establish that diagnosis for all reported events. Perioperative precautions remain appropriate.
- name: Rhabdomyolysis
  category: Neuromuscular
  description: Muscle breakdown can occur after exercise or during anesthesia-associated contracture. It is an uncommon reported complication, and its population frequency is unknown. The 2020 cohort already included exertional cases; the 2026 case report adds another clinical presentation.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: He also experienced two episodes of rhabdomyolysis following exercise at ages 19 and 22 with creatine kinase levels up to 221 600 IU/l and 100 000 IU/l, respectively.
    explanation: Full-text recurrent exertional injury in one patient.
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: One other patient (Patient N15) experienced an episode of exertional rhabdomyolysis.
    explanation: A second patient establishes that the finding predates the recent report.
  - reference: PMID:41926432
    reference_title: "Rare Brody myopathy: A case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Patient is a 19-year-old woman presenting with exercise-induced rhabdomyolysis.
    explanation: Recent clinical case; the abstract does not provide the complete biallelic genotype.
  phenotype_term:
    preferred_term: Rhabdomyolysis
    term:
      id: HP:0003201
      label: Rhabdomyolysis
  sequelae:
  - target: Elevated circulating creatine kinase activity
    description: Muscle breakdown releases creatine kinase into the circulation.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:32040565
      reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: He also experienced two episodes of rhabdomyolysis following exercise at ages 19 and 22 with creatine kinase levels up to 221 600 IU/l and 100 000 IU/l, respectively.
      explanation: Muscle breakdown was accompanied by marked circulating CK release; this link concerns episodes of rhabdomyolysis, not baseline CK elevation.
- name: Generally preserved muscle strength and bulk
  category: Neuromuscular
  description: 'Clinical strength and bulk are usually preserved, and athletic appearance is common. This is a typical pattern rather than an exclusion of all weakness: three cohort patients had mild objective proximal weakness. Severe progressive weakness or atrophy should prompt assessment for an alternative or additional disorder.'
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Physical examination revealed no muscle atrophy in any of the patients (0/33) and mild proximal muscle weakness in 3/35 patients
    explanation: Separates absent clinical atrophy from a documented minority with weakness.
  - reference: PMID:38373275
    reference_title: "Brody Disease, an Early-Onset Myopathy With Delayed Relaxation and Abnormal Gait: A Case Series of 9 Children."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Muscle strength and mass was normal, and several children even had an athletic appearance.
    explanation: The pediatric series supports preserved strength and mass in its nine children.
- name: Proximal muscle weakness
  category: Neuromuscular
  description: Mild proximal weakness was documented on examination in 3/35 cohort patients, distinct from the more frequent subjective complaint of weakness. A later adult case describes mild progression. Pronounced progressive weakness is not the usual course.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: mild proximal muscle weakness in 3/35 patients
    explanation: Objective weakness is reported and should not be encoded as universally absent.
  - reference: PMID:38125752
    reference_title: "Case report: Revealing the rare-a Brody Disease patient from Turkey expanding the phenotype."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: mild progressive proximal muscle weakness in the lower extremities
    explanation: Individual adult observation in a reported homozygous ATP2A1 case; not a population prognosis.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Proximal muscle weakness
    term:
      id: HP:0003701
      label: Proximal muscle weakness
- name: Absence of myotonic discharges
  category: Neuromuscular
  description: Myotonic discharges were absent in all 30 cohort patients tested. This electrophysiological finding does not imply that percussion myotonia is always absent on examination. Electrically silent contractures were detected in 18/28 tested patients.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: None of the patients had myotonic discharges on EMG (n = 30). Silent contractures were present in 18/28 patients
    explanation: Distinguishes absent myotonic discharges from incompletely elicited contractures.
- name: Percussion myotonia
  category: Neuromuscular
  description: Reported clinically in 4/34 cohort patients despite absent myotonic discharges. The term records the bedside observation and should not be taken as proof of a sarcolemmal channelopathy.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Percussion myotonia was reported in 4/34 patients
    explanation: Directly contradicts a blanket exclusion of the clinical sign.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Percussion myotonia
    term:
      id: HP:0010548
      label: Percussion myotonia
- name: Elevated circulating creatine kinase activity
  category: Laboratory
  description: Resting creatine kinase was normal in 12/24 patients and slightly to moderately elevated in 12/24, ranging across the whole tested group from 50 to 1300 IU/L. Markedly higher levels occur during rhabdomyolysis.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Creatine kinase was considered normal in 12/24 patients and slightly to moderately elevated in 12/24 patients
    explanation: Cohort denominator supports the frequency band and distinguishes resting values from acute muscle injury.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Elevated circulating creatine kinase activity
    term:
      id: HP:0003236
      label: Elevated circulating creatine kinase activity
- name: Myalgia
  category: Neuromuscular
  description: Pain was reported in 20/34 cohort patients, often generalized; some affected individuals have painless stiffness.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Myalgia was commonly reported (20/34) and usually had a generalized distribution.
    explanation: Direct cohort result supports the frequency band.
  - reference: PMID:37332993
    reference_title: "Case report: Clinical and molecular characterization of two siblings affected by Brody myopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: two siblings presenting childhood-onset exercise-induced muscle stiffness without pain
    explanation: Documents that pain is not obligatory.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Myalgia
    term:
      id: HP:0003326
      label: Myalgia
- name: Muscle cramps
  category: Neuromuscular
  description: Painful sustained contractures may occur at rest or with exercise. The cohort reported either setting in 18/34 patients; this combined denominator is not an exercise-only prevalence estimate.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Patients variably reported muscle cramps (defined as involuntary and painful sustained muscle contractures) at rest or during exercise (18/34).
    explanation: Reports the authors’ definition and combined rest/exercise denominator.
  phenotype_term:
    preferred_term: Muscle cramps
    term:
      id: HP:0003394
      label: Muscle spasm
  frequency: FREQUENT
- name: Skeletal muscle hypertrophy
  category: Neuromuscular
  description: Hypertrophic muscles were described in 10/34 cohort patients, whereas athletic appearance was recorded in 20/30. The two observations are related but are not equivalent measurements of muscle enlargement.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Several patients were described as having an athletic appearance (20/30) and/or as having hypertrophic muscles (10/34).
    explanation: Uses the hypertrophy-specific denominator rather than applying the athletic-build frequency to muscle hypertrophy.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Skeletal muscle hypertrophy
    term:
      id: HP:0003712
      label: Skeletal muscle hypertrophy
- name: Difficulty running
  category: Neuromuscular
  description: Running and sports can be limited by exercise-induced delayed relaxation despite preserved strength. This was a presenting complaint in all nine children in the 2024 series.
  evidence:
  - reference: PMID:38373275
    reference_title: "Brody Disease, an Early-Onset Myopathy With Delayed Relaxation and Abnormal Gait: A Case Series of 9 Children."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: All presented with exercise-induced delayed relaxation, reported as difficulty running and performing sports.
    explanation: Core functional presentation in the pediatric cohort.
  phenotype_term:
    preferred_term: Difficulty running
    term:
      id: HP:0009046
      label: Difficulty running
- name: Gait disturbance
  category: Neuromuscular
  description: Abnormal walking and running patterns can be an early presentation in children and may prompt evaluation for developmental or movement disorders before the relaxation defect is recognized.
  evidence:
  - reference: PMID:38373275
    reference_title: "Brody Disease, an Early-Onset Myopathy With Delayed Relaxation and Abnormal Gait: A Case Series of 9 Children."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: However, the walking and running patterns were abnormal.
    explanation: Direct pediatric observation; not evidence of a primary central nervous system disorder.
  phenotype_term:
    preferred_term: Gait disturbance
    term:
      id: HP:0001288
      label: Gait disturbance
- name: Frequent falls
  category: Neuromuscular
  description: Frequent falls accompanied difficulty running and climbing stairs in two affected siblings. A general population frequency has not been established.
  evidence:
  - reference: PMID:37332993
    reference_title: "Case report: Clinical and molecular characterization of two siblings affected by Brody myopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Both the probands display difficulty in climbing stairs and running, frequent falls, delayed muscle relaxation after exertion.
    explanation: Case-level clinical support from two genetically investigated siblings.
  phenotype_term:
    preferred_term: Frequent falls
    term:
      id: HP:0002359
      label: Frequent falls
- name: Type 2 muscle fiber atrophy
  category: Histopathology
  description: Type II atrophy occurred in 13/17 assessed biopsies; occasional type I atrophy was also present. Histological atrophy may coexist with preserved clinical bulk or an athletic appearance.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Atrophy of type II fibres was seen in 76% (13/17) of patients, of which two also demonstrated type I atrophy.
    explanation: Biopsy-selected cohort proportion; not generalized clinical muscle wasting.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Type 2 muscle fiber atrophy
    term:
      id: HP:0003554
      label: Type 2 muscle fiber atrophy
- name: Increased variability in muscle fiber diameter
  category: Histopathology
  description: Fibre-size variability was markedly increased in 11/12 biopsies with available assessment.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Variability of muscle fibre size was markedly increased in 92% (11/12) of samples.
    explanation: Specimen-based denominator supports the morphology finding.
  frequency: VERY_FREQUENT
  phenotype_term:
    preferred_term: Increased variability in muscle fiber diameter
    term:
      id: HP:0003557
      label: Increased variability in muscle fiber diameter
- name: Centrally nucleated skeletal muscle fibers
  category: Histopathology
  description: Increased internal nuclei are a common biopsy finding; explicit nuclear centralization and clumping were reported in one serially biopsied patient. The frequency of increased internal nuclei must not be applied to centrally positioned nuclei specifically.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Nuclear centralization and nuclear clumping was sporadically seen in the second biopsy
    explanation: Direct support for the more specific morphology; avoids conflating all internal with central nuclei.
  phenotype_term:
    preferred_term: Centrally nucleated skeletal muscle fibers
    term:
      id: HP:0003687
      label: Centrally nucleated skeletal muscle fibers
- name: Delayed eyelid relaxation
  category: Neuromuscular
  description: Difficulty relaxing the eyelids after forceful or repeated closure reflects orbicularis oculi involvement. Eyelid symptoms were reported in 24/38 patients; delayed relaxation was elicited in 19/31 after repetitive and 17/29 after sustained closure.
  frequency: FREQUENT
  phenotype_term:
    preferred_term: Delayed eyelid relaxation
  review_notes: No matching HPO term was found by searching eyelid relaxation; electrical eyelid myotonia would misrepresent this relaxation defect, which can lack myotonic discharges.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: The muscle groups predominantly affected were lower limbs (38/38), upper limbs (33/38), and eyelids (24/38).
    explanation: Reported eyelid involvement in 24/38 cohort patients.
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Delayed relaxation specifically of the eyelids was seen after repetitive eyelid-closure in 19/31 patients and after sustained forceful eyelid-closure in 17/29 patients.
    explanation: Separate examination maneuvers and tested denominators; both support delayed eyelid relaxation.
genetic:
- name: ATP2A1
  gene_term:
    preferred_term: ATP2A1
    term:
      id: hgnc:811
      label: ATP2A1
  relationship_type: CAUSATIVE
  inheritance:
  - name: Autosomal recessive
    inheritance_term:
      preferred_term: Autosomal recessive inheritance
      term:
        id: HP:0000007
        label: Autosomal recessive inheritance
  notes: >-
    ATP2A1 encodes SERCA1. Pathogenic variants include truncating and splice changes, missense substitutions,
    in-frame deletions and exon/whole-gene deletions. Loss of expression, accelerated degradation and intrinsic
    transport defects are distinct, potentially overlapping routes. Corrector responsiveness cannot be inferred
    from the label missense alone; splice variants do not invariably abolish protein production.
  evidence:
  - *id008
  - *id003
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: 'DNA alterations at the ATP2A1 gene locus represent the whole spectrum of mutation types: whole gene deletion, single exon deletion, splice site mutations, small exonic frameshift deletions or insertions, missense substitutions, and in-frame small deletions'
    explanation: The patient series establishes the observed variant spectrum.
  - reference: PMID:37332993
    reference_title: "Case report: Clinical and molecular characterization of two siblings affected by Brody myopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: This alteration is expected to preserve the reading frame.
    explanation: The experimentally demonstrated exon-4 splice skip cautions against treating every splice allele as a complete null.
biochemical:
- name: Sarcoplasmic reticulum calcium ATPase activity
  presence: DECREASED
  notes: Whole-muscle calcium-dependent ATPase activity is reduced in genetically confirmed Brody disease. In the optimized 2026 assay, four patient samples averaged 30.0 ± 4.2 mU/mg protein versus 86.7 ± 25.1 in 28 controls (mean ± SD). This is a compound SERCA1/SERCA2 assay with potential PMCA contribution. The small control-versus-case comparison does not establish specificity against other myopathies, and results require clinical and genetic interpretation.
  evidence:
  - reference: PMID:41938373
    reference_title: Sarco/endoplasmatic reticulum calcium ATPase activity in healthy muscle and Brody disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Brody disease muscle samples (30.0 ± 4.2 mU/mg protein) compared to controls (86.7 ± 25.1 mU/mg protein)
    explanation: Quantitative values from the specified assay and small clinical sample.
  - reference: PMID:41938373
    reference_title: Sarco/endoplasmatic reticulum calcium ATPase activity in healthy muscle and Brody disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: with the measurement of compound SERCA activity there is no differentiation between SERCA1 and SERCA2 activity.
    explanation: Explicit analytical specificity limit.
  reference_ranges:
  - lower_bound: 36.6
    unit: mU/mg
    population: Study-specific frozen quadriceps samples from 28 healthy controls; optimized molybdate-Fe(II) phosphate assay
    notes: Lower limit calculated as control mean minus two standard deviations; mU per mg total protein. Not a universal clinical cutoff. No upper reference limit was established. Patient samples included two quadriceps and two deltoid biopsies; age, sex, muscle site and other myopathies require further validation.
    evidence:
    - reference: PMID:41938373
      reference_title: Sarco/endoplasmatic reticulum calcium ATPase activity in healthy muscle and Brody disease.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: resulting in an overall lower limit of normal of 36.6 mU/mgP (mean – 2xSD).
      explanation: Source-defined one-sided lower reference limit, not an inferred interval from the patient mean.
- name: SERCA1 protein abundance
  presence: DECREASED
  notes: Western blotting generally shows markedly reduced or absent SERCA1 in tested patient muscle. Immunohistochemistry can appear normal. Protein quantity and transport activity are complementary measurements rather than interchangeable tests.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: All immunoblot analyses demonstrated absent or severely decreased amounts of SERCA protein.
    explanation: Patient protein-abundance result.
  - reference: PMID:41938373
    reference_title: Sarco/endoplasmatic reticulum calcium ATPase activity in healthy muscle and Brody disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: western blots provide information on SERCA1 protein content but not on its function and vice versa for the SERCA activity assay.
    explanation: Explains why abundance does not replace a functional assay.
histopathology:
- name: Type II fibre atrophy and fibre-size variability
  description: Mild myopathic changes commonly include preferential type II atrophy, fibre-size variability and increased internal nuclei. Findings are supportive and nonspecific; type I changes also occur. Clinical bulk can remain normal.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Systematic re-evaluation of the biopsy reports showed fibre type II atrophy, increased fibre size variability, and an increased number of internal nuclei.
    explanation: Summarizes the systematic biopsy review.
- name: Sarcoplasmic reticulum remodeling
  description: One patient biopsy showed dilated lateral cisternae and proliferating tubular SR elements. This ultrastructural observation should not be used alone as evidence for decreased protein expression.
  evidence:
  - reference: PMID:20142766
    reference_title: "Brody disease: insights into biochemical features of SERCA1 and identification of a novel mutation."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Ultrastructural examination revealed dilatation of lateral cisternae and proliferation of tubular elements of the sarcoplasmic reticulum.
    explanation: Direct human ultrastructural result.
- name: Usually limited myonecrosis
  description: Discrete necrosis occurred in one reviewed biopsy, with degeneration in two additional specimens. Extensive necrosis is not the typical baseline pattern, but acute rhabdomyolysis and more severe bovine muscle injury are documented.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Discrete necrosis was found in only one biopsy (Patient L18). The same biopsy also showed sparse regeneration, and two other biopsies showed degeneration
    explanation: Qualifies the usual absence rather than claiming muscle injury never occurs.
diagnosis:
- name: Clinical provocation and electromyography
  description: Examine relaxation after repeated rapid contractions and sustained hand grip or eyelid closure. Absence of myotonic discharges with clinically evident delayed relaxation suggests Brody disease. Silent contractures may need active provocation and are not always elicited; normal routine EMG does not exclude the diagnosis.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
    snippet: when EMG shows no myotonic discharges in patients clinically suspected of having a myotonic disorder, provocation of possible silent contractures is recommended by performing rapid contractions during EMG.
    explanation: Clinical testing recommendation from the cohort.
- name: ATP2A1 sequencing with deletion analysis when indicated
  description: Sequence ATP2A1 directly or use an appropriate myopathy panel/exome approach. Ensure exon and gene copy-number changes are assessed, particularly when clinical and functional evidence is convincing but only one pathogenic allele is found. The pediatric series recommends including ATP2A1 in congenital-myopathy, developmental/movement-disorder and muscle-channelopathy panels.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
    snippet: we recommend direct sequencing of the ATP2A1 gene or next generation sequencing with a myopathy panel
    explanation: Recommended molecular confirmation.
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: This led to the discovery of an additional large-scale deletion of exon 9, confirming Brody disease as the diagnosis.
    explanation: An unresolved second allele was found after further analysis prompted by biochemical deficiency.
  - reference: PMID:38373275
    reference_title: "Brody Disease, an Early-Onset Myopathy With Delayed Relaxation and Abnormal Gait: A Case Series of 9 Children."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
    snippet: We propose that ATP2A1 should be added to gene panels for congenital myopathies, developmental and movement disorders, and muscle channelopathies.
    explanation: Expands pediatric diagnostic recognition without redefining Brody disease as a primary neurodevelopmental disorder.
- name: Complementary SERCA activity and protein assays
  description: Muscle calcium-ATPase measurement and SERCA1 western blot can support interpretation of uncertain ATP2A1 variants. The 2026 optimized assay provides laboratory-specific quantitative data. Reduced compound activity is not a stand-alone proof of variant pathogenicity or Brody disease because other myopathies and assay contributors can alter it.
  evidence:
  - reference: PMID:41938373
    reference_title: Sarco/endoplasmatic reticulum calcium ATPase activity in healthy muscle and Brody disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
    snippet: For ATP2A1 variants of uncertain significance, decreased SERCA activity can provide supportive evidence for the diagnosis of Brody disease
    explanation: Defines supportive clinical use rather than automatic reclassification.
  - reference: PMID:41938373
    reference_title: Sarco/endoplasmatic reticulum calcium ATPase activity in healthy muscle and Brody disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: it is possible that SERCA activity is also abnormal in other (calcium related) myopathies
    explanation: Disease-specificity limitation from the assay study.
- name: SERCA1 immunohistochemistry limitations
  description: Normal or near-normal immunostaining does not exclude reduced protein content or dysfunctional SERCA1. Western blot and functional assessment can be abnormal when staining appears preserved.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: SERCA1 staining revealed a severe reduction in six patients (6/12) and was normal in the other patients (6/12)
    explanation: Observed false reassurance from staining alone.
  - reference: PMID:23911890
    reference_title: SERCA1 protein expression in muscle of patients with Brody disease and Brody syndrome and in cultured human muscle fibers.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: SERCA1 reactivity was observed in type 2 muscle fibers of patients with and without ATP2A1 mutations and staining intensity was similar in patients and controls.
    explanation: Independent study supports limited discriminatory value.
inheritance:
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    Biallelic pathogenic ATP2A1 variants cause autosomal recessive Brody disease. Heterozygous relatives in
    reported families generally lack the Brody phenotype. When both parents carry one familial pathogenic allele,
    each pregnancy has the standard recessive recurrence risk of 25%; molecular phasing and family testing
    are important for counseling.
  evidence:
  - *id008
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Heterozygous family members of patients (carriers) did not exhibit the Brody disease phenotype
    explanation: Family histories support unaffected carriers, although carrier phenotyping was not systematically collected.
treatments:
- name: Trigger-Free Anaesthesia and Perioperative Monitoring
  description: Plan anesthesia with specialist precautions because of reported anesthesia-associated rigidity, rhabdomyolysis and MH-like reactions. The cohort recommends avoiding succinylcholine and inhalational agents and monitoring vital signs including core temperature. This management recommendation does not establish a quantified risk of classic malignant hyperthermia or prove a reduction in mortality.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: Therapeutic Procedure
    term:
      id: NCIT:C49236
      label: Therapeutic Procedure
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
    snippet: avoid administration of succinylcholine and inhalational agents, and monitor vital functions including core temperature
    explanation: The cohort recommends perioperative precautions despite uncertainty about classic MH susceptibility.
- name: Symptomatic Pharmacotherapy
  description: Symptomatic drugs often provide limited benefit or unacceptable adverse effects. In the 2020 cohort, mexiletine improved symptoms in one of two exposed patients but was stopped because of side effects; carbamazepine, ibuprofen, nifedipine and other tried agents did not provide sustained benefit. Drug selection and monitoring require individual clinical assessment.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Symptomatic treatment was mostly ineffective or produced unacceptable side effects.
    explanation: Overall cohort experience limits claims of general symptomatic efficacy.
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Mexiletine improved symptoms in one patient but was similarly stopped because of side effects.
    explanation: Captures a transient individual response and its tolerability limit.
- name: Dantrolene
  description: Dantrolene reduces skeletal-muscle calcium release and is used off label for symptoms in selected patients. Five exposed patients in the 2020 series had no reported benefit, whereas a 2026 single case reported marked improvement. These uncontrolled observations indicate variable response, not established efficacy or an explained genotype-specific difference.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: dantrolene
      term:
        id: CHEBI:4317
        label: dantrolene
  evidence:
  - reference: PMID:41926432
    reference_title: "Rare Brody myopathy: A case report."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Treatment with dantrolene sodium resulted in marked clinical improvement.
    explanation: Single uncontrolled Brody-labeled clinical case; this supports an individual response, not established general efficacy.
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: REFUTE
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: dantrolene (n = 5) ... The other medications showed no effect
    explanation: The full treatment paragraph identifies dantrolene among agents without observed benefit, in contrast to verapamil and mexiletine.
  target_mechanisms:
  - target: Prolonged Cytosolic Calcium Elevation
    description: Reducing calcium release may lower the load that deficient SERCA1 cannot promptly clear.
    treatment_effect: MODULATES
    evidence:
    - reference: PMID:32040565
      reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      directness: INDIRECT
      quote_role: REVIEW_SYNTHESIS
      snippet: Verapamil and dantrolene, drugs that limit the Ca2+ release from the sarcoplasmic reticulum
      explanation: Mechanistic rationale discussed by the cohort authors, not direct calcium measurements in the responding case.
- name: Verapamil
  description: In the 2020 retrospective series, three of nine exposed patients improved, but two stopped because of adverse effects. One patient received successful long-term treatment. This supports possible individualized symptomatic benefit rather than predictable efficacy.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: verapamil
      term:
        id: CHEBI:9948
        label: verapamil
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Verapamil improved symptoms in three patients but was stopped in two of them because of side effects.
    explanation: Three of nine exposed patients reported benefit; only one continued successfully long term.
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: only 1 of 18 treated patients received long-term successful treatment (Patient N15; verapamil).
    explanation: Distinguishes long-term success from short-lived response across the treated cohort.
  target_mechanisms:
  - target: Prolonged Cytosolic Calcium Elevation
    description: The proposed symptomatic approach reduces calcium release rather than restoring SERCA1 expression.
    treatment_effect: MODULATES
    evidence:
    - reference: PMID:32040565
      reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      directness: INDIRECT
      quote_role: REVIEW_SYNTHESIS
      snippet: Verapamil and dantrolene, drugs that limit the Ca2+ release from the sarcoplasmic reticulum
      explanation: Mechanistic rationale for reducing cytosolic calcium burden.
- name: CFTR Correctors (Investigational)
  description: C17, C4 and C9 increase abundance of selected bovine SERCA1 mutants in heterologous cells. Local C17 injections in two affected calves increased SR-associated SERCA1 and calcium-ATPase activity; whole-animal functional recovery and systemic safety were not established. C17 failed to improve key morphological and locomotor outcomes in the S766F accordion zebrafish model, which has a different molecular defect. Lumacaftor and tezacaftor were relatively ineffective in the tested cell assay. Human therapeutic benefit remains unproven.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: C17 CFTR corrector
  evidence:
  - reference: PMID:41206505
    reference_title: "CFTR corrector C17 rescues defective SERCA1 in bovine pseudomyotonia: a potential therapy for Brody myopathy."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    quote_role: PRIMARY_RESULT
    snippet: The functional assay indicated that SR-enriched membrane fraction obtained from C17 treated muscle fibers displayed in parallel an increase in maximal Ca2+-ATPase activity
    explanation: Biochemical improvement after local intramuscular treatment in two affected calves; not demonstrated systemic or clinical efficacy in humans.
  - reference: PMID:39273176
    reference_title: The Accordion Zebrafish tq206 Mutant in the Assessment of a Novel Pharmaceutical Approach to Brody Myopathy.
    supports: REFUTE
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    quote_role: PRIMARY_RESULT
    snippet: the Tq206−/− embryos treated with C17 (orange color) did not exhibit any significant differences after treatment, neither in terms of body length (Figure 5A) or tail curvature angles (Figure 5B).
    explanation: The S766F homozygous zebrafish model did not show morphological rescue; locomotor rescue was also not significant.
  - reference: PMID:41206505
    reference_title: "CFTR corrector C17 rescues defective SERCA1 in bovine pseudomyotonia: a potential therapy for Brody myopathy."
    supports: REFUTE
    evidence_source: IN_VITRO
    directness: INDIRECT
    quote_role: PRIMARY_RESULT
    snippet: Other tested CFTR correctors including VX809 ... VX661 ... and the molecule glafenine, were less effective or almost totally ineffective in rescuing R164H mutant SERCA1.
    explanation: Approved cystic-fibrosis drugs cannot be assumed to reproduce the experimental C17 result.
  target_mechanisms:
  - target: Proteasomal Degradation of Misfolded SERCA1
    description: The strategy preserves abundance of selected unstable but catalytically competent pumps; its precise molecular mechanism is not fully established.
    treatment_effect: MODULATES
    evidence:
    - reference: PMID:41206505
      reference_title: "CFTR corrector C17 rescues defective SERCA1 in bovine pseudomyotonia: a potential therapy for Brody myopathy."
      supports: SUPPORT
      evidence_source: IN_VITRO
      directness: INDIRECT
      quote_role: PRIMARY_RESULT
      snippet: the incubation with CFTR correctors C17, C4 and C9, induced an increase in the expression level of SERCA1 mutant almost equivalent to that of MG132-treated cells
      explanation: Expression rescue in transfected cells; not proof of direct proteasome inhibition.
  notes: Eligibility would require a protein that can be rescued and retains useful transport function, rather than simply a missense classification. Complete absence of functional protein is not addressed by this approach. The two-calf experiment used local muscle dosing and technical assay replicates; cytotoxicity varied by cell model and therapeutic-index/pharmacokinetic work was incomplete.
- name: Proteasome Inhibition (Experimental Proof of Mechanism)
  description: MG132 restores mutant SERCA1 abundance and function in cellular and bovine muscle-explant experiments involving selected destabilized variants. This establishes a degradation mechanism and a rescue assay; there is no demonstrated clinical benefit or safe systemic regimen for Brody patients.
  therapeutic_modality: SMALL_MOLECULE
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: MG132
      term:
        id: CHEBI:75142
        label: N-benzyloxycarbonyl-L-leucyl-L-leucyl-L-leucinal
  evidence:
  - &id009
    reference: PMID:25288803
    reference_title: Inhibition of ubiquitin proteasome system rescues the defective sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA1) protein causing Chianina cattle pseudomyotonia.
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    quote_role: PRIMARY_RESULT
    snippet: The treatment with MG132, an inhibitor of ubiquitin proteasome system, rescues the expression level and membrane localization of the SERCA1 mutant in a heterologous cellular model.
    explanation: Proof of mechanism for bovine R164H in cells; not a treatment recommendation for patients.
  - reference: PMID:36293223
    reference_title: Differential Analysis of Gly211Val and Gly286Val Mutations Affecting Sarco(endo)plasmic Reticulum Ca(2+)-ATPase (SERCA1) in Congenital Pseudomyotonia Romagnola Cattle.
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: INDIRECT
    quote_role: PRIMARY_RESULT
    snippet: incubation of G211V-transfected cells with proteasome inhibitor MG132 led to a significant increase in microsomal Ca2+ ATPase activity
    explanation: Biochemical rescue complements increased protein abundance.
  target_mechanisms:
  - target: Proteasomal Degradation of Misfolded SERCA1
    description: Blocking the proteasome prevents premature mutant-protein disposal.
    treatment_effect: INHIBITS
    evidence:
    - *id009
- name: Activity Pacing and Trigger Management
  description: Adjust rapid repetitive activity to individual tolerance and use rest breaks to relieve stiffness. Cold exposure can worsen symptoms, so temperature and activity adjustments may help symptom avoidance. This is pragmatic supportive management; the cited evidence does not establish a standardized physical-therapy or warm-up protocol.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Therapeutic Procedure
    term:
      id: NCIT:C49236
      label: Therapeutic Procedure
  evidence:
  - reference: PMID:25614869
    reference_title: Exome analysis identifies Brody myopathy in a family diagnosed with malignant hyperthermia susceptibility.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
    snippet: Brody disease has a mild presentation when muscular activity is paced at tolerable levels, but becomes acute with rapid, repetitive exercise.
    explanation: Clinical discussion supports pacing as a practical response to the exertional phenotype.
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: INDIRECT
    quote_role: PRIMARY_RESULT
    snippet: The majority of patients mentioned an increase of symptoms upon exposure to cold temperatures (25/36).
    explanation: Observed trigger provides an indirect rationale for temperature management.
- name: Genetic Counselling
  description: Discuss autosomal recessive inheritance, confirm the familial variants and their phase, and offer appropriate family testing. For two carrier parents, the usual recurrence risk is 25% per pregnancy. Identifying affected relatives also allows communication of perioperative precautions; heterozygous carrier status alone is not equivalent to the affected phenotype.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: Genetic Counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:37332993
    reference_title: "Case report: Clinical and molecular characterization of two siblings affected by Brody myopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: The bi-allelic inheritance was verified by Sanger sequencing in the unaffected parents.
    explanation: Family segregation provides direct evidence for recessive counseling.
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Heterozygous family members of patients (carriers) did not exhibit the Brody disease phenotype
    explanation: Observed carrier status supports distinguishing carriers from affected relatives; this was not systematically assessed.
animal_models:
- name: 'Bovine congenital pseudomyotonia: Chianina and Romagnola ATP2A1 variants'
  species: Cattle
  genotype: R164H homozygosity; G211V/G286V cis allele homozygosity or compound heterozygosity with R164H
  publication: PMID:18786632
  description: Naturally occurring recessive disease produces exercise-induced stiffness, delayed relaxation and reduced SERCA1 abundance/activity. Functional separation of the Romagnola cis variants identifies G211V as pathogenic and G286V as largely benign. Local C17 treatment in two compound-heterozygous calves improved muscle biochemical endpoints, but systemic clinical efficacy was not established.
  modeled_mechanisms:
  - target: Reduced SERCA1 Density at the Sarcoplasmic Reticulum Membrane
    description: Models low SERCA1 abundance in skeletal muscle, with variant- and species-specific limits.
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    evidence:
    - reference: PMID:23046865
      reference_title: Pseudomyotonia in Romagnola cattle caused by novel ATP2A1 mutations.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: the amount of SERCA1 protein was decreased in the pathological samples with respect to control samples
      explanation: Whole-animal disease specimens show reduced abundance; this is not direct evidence of the same molecular route in every human variant.
  - target: Impaired Calcium Reuptake into the Sarcoplasmic Reticulum
    description: Reduced calcium-ATPase activity in affected muscle models loss of reuptake capacity.
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    evidence:
    - reference: PMID:18786632
      reference_title: "Identification of a missense mutation in the bovine ATP2A1 gene in congenital pseudomyotonia of Chianina cattle: an animal model of human Brody disease."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: SERCA1 activity in affected animals was decreased by about 70%
      explanation: Founding Chianina study provides a functional muscle readout.
  notes: The 2012 abstract contains inconsistent amino-acid nomenclature; R164H and the distinction between G211V and G286V follow the corrected body text and the 2022 functional study. Degeneration can be more marked than in typical human biopsies.
- name: Dutch Improved Red and White calf with ATP2A1 R559C
  species: Cattle
  genotype: ATP2A1 p.Arg559Cys
  publication: PMID:20547455
  description: A naturally affected calf had exercise-induced stiffness and low SERCA1 activity. The same variant is associated with a more severe respiratory course in Belgian Blue cattle, indicating context-dependent expression. Increased PMCA and broadly distributed mitochondrial markers were observed without SERCA2 compensation.
  modeled_mechanisms:
  - target: Compensatory Calcium Extrusion and Handling
    description: Provides expression-level clues to compensatory calcium handling, not direct proof of increased extrusion flux.
    relationship: PARTIALLY_RECAPITULATES
    fidelity: LOW
    evidence:
    - reference: PMID:26482047
      reference_title: Fast-twitch skeletal muscle fiber adaptation to SERCA1 deficiency in a Dutch Improved Red and White calf pseudomyotonia case.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: an increased expression of sarcolemmal calcium extrusion pump
      explanation: Protein expression supports the candidate adaptation; no selective intervention establishes causal rescue.
- name: accordion zebrafish, including atp2a1 tq206 S766F
  species: Zebrafish
  genotype: atp2a1 accordion alleles; tq206 S766F homozygotes and heterozygotes
  publication: PMID:15469975
  description: Mutants show prolonged calcium transients and simultaneous bilateral trunk contraction. The tq206 S766F homozygote has severe larval abnormalities and early lethality, unlike the usually mild human course. C17 did not significantly rescue key morphological or locomotor endpoints in the 2024 experiment. Heterozygotes had largely preserved larval locomotion, although adult histology showed abnormalities.
  modeled_mechanisms:
  - target: Impaired Calcium Reuptake into the Sarcoplasmic Reticulum
    description: Recapitulates impaired calcium clearance after excitation, with species-specific behavioral and developmental readouts.
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    evidence:
    - reference: PMID:15469975
      reference_title: "accordion, a zebrafish behavioral mutant, has a muscle relaxation defect due to a mutation in the ATPase Ca2+ pump SERCA1."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: In vivo imaging of muscle Ca2+ transients revealed that cytosolic Ca2+ decay was significantly slower in acc muscle.
      explanation: Direct in-vivo calcium-transient measurement.
  - target: Intrinsic SERCA1 Calcium-Transport Defect
    description: S766F is a useful contrast to unstable, activity-retaining mutants; preserved expression and lack of corrector response are consistent with a functional defect.
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    evidence:
    - reference: PMID:39273176
      reference_title: The Accordion Zebrafish tq206 Mutant in the Assessment of a Novel Pharmaceutical Approach to Brody Myopathy.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: Administration of the CFTR C17 corrector to Tq206−/− siblings exhibited no difference or improvement in morphological traits and swimming performance.
      explanation: Negative rescue in the S766F model constrains the therapeutic generalization.
  notes: The 2024 study inferred impaired intrinsic S766F function from phenotype, expression and structural context; it did not directly establish the same calcium-affinity defect measured for human P789L. Embryonic/larval severity and early death limit modeling of human natural history.
- name: Atp2a1-null mouse
  species: Mouse
  genotype: Atp2a1 homozygous null
  publication: PMID:12556521
  description: Constitutive SERCA1 loss produces marked reduction in calcium transport, neonatal diaphragm dysfunction and death shortly after birth. The model captures severe loss of pump function but not the usually survivable human course. Diaphragm fibre composition, species-specific adaptation and residual allele activity may contribute to the mismatch.
  modeled_mechanisms:
  - target: Impaired Calcium Reuptake into the Sarcoplasmic Reticulum
    description: Recapitulates deficient calcium transport in diaphragm and skeletal muscle despite a much more severe clinical outcome.
    relationship: PARTIALLY_RECAPITULATES
    fidelity: MODERATE
    evidence:
    - reference: PMID:12556521
      reference_title: Targeted disruption of the ATP2A1 gene encoding the sarco(endo)plasmic reticulum Ca2+ ATPase isoform 1 (SERCA1) impairs diaphragm function and is lethal in neonatal mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: The V(max) of Ca(2+) transport activity in mutant diaphragm and skeletal muscle was reduced by 80% compared with wild-type muscle
      explanation: Direct functional consequence of the engineered null.
  - target: Compensatory Calcium Extrusion and Handling
    description: The assayed compensatory changes were not detected in this lethal neonatal model.
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    evidence:
    - reference: PMID:12556521
      reference_title: Targeted disruption of the ATP2A1 gene encoding the sarco(endo)plasmic reticulum Ca2+ ATPase isoform 1 (SERCA1) impairs diaphragm function and is lethal in neonatal mice.
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: No compensatory responses were detected in analysis of mRNAs encoding other Ca(2+) handling proteins or of protein levels.
      explanation: Negative expression-level result in newborn mice; it does not prove all possible compensatory flux is absent.
    limitations: Comparison is with proposed human adaptation, whose functional magnitude remains uncertain. Constitutive complete loss, neonatal respiratory demand and species-specific muscle composition all limit inference.
discussions:
- discussion_id: brody_compensation_mechanism
  prompt: >-
    Which calcium-handling adaptations preserve muscle function in humans with severe SERCA1 deficiency?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - pathophysiology#Compensatory Calcium Extrusion and Handling
  rationale: >-
    One affected human biopsy showed increased SERCA2, whereas most tested biopsies did not. An affected calf
    showed increased PMCA expression and altered mitochondrial-marker distribution without SERCA2 compensation.
    These are expression-level observations rather than selective functional-rescue experiments. The candidate
    mechanisms need not compete exclusively and could vary by patient, fibre type or genetic background.
  proposed_experiments:
  - experiment_id: brody_compensation_profiling
    name: Calcium-handling protein profiling in genotyped Brody muscle
    description: >-
      Quantify SERCA2, PMCA and other candidate calcium-handling proteins in genotyped patient muscle, and
      measure calcium clearance with selective perturbations where feasible. Stratify by fibre type and residual
      SERCA1 function to distinguish expression changes from functional compensation.
  - experiment_id: brody_single_nucleus_rnaseq
    name: Fibre-type-resolved single-nucleus RNA sequencing of Brody muscle
    description: >-
      Compare fibre-type-resolved transcriptional programs in patient muscle and controls, followed by protein
      and calcium-flux validation. Transcript abundance alone would not establish a compensatory transport
      mechanism.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
    snippet: Future research would be needed to test if similar compensatory mechanisms can be identified in patients with Brody disease.
    explanation: The cohort identifies the remaining translational gap.
  - reference: PMID:26482047
    reference_title: Fast-twitch skeletal muscle fiber adaptation to SERCA1 deficiency in a Dutch Improved Red and White calf pseudomyotonia case.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: INDIRECT
    quote_role: PRIMARY_RESULT
    snippet: Calcium removal mechanisms, operating in muscle fibers as compensatory response aimed at lowering excessive cytoplasmic calcium concentration caused by SERCA1 deficiency, could explain the difference in severity of clinical signs.
    explanation: The bovine authors frame compensation as a proposed explanation rather than a proven cause.
- discussion_id: brody_mouse_model_mismatch
  prompt: >-
    Why is constitutive SERCA1 loss neonatally lethal in mice while human Brody disease usually permits long-term
    survival?
  kind: HUMAN_MODEL_MISMATCH
  status: OPEN
  attaches_to:
  - pathophysiology#Compensatory Calcium Extrusion and Handling
  - pathophysiology#Reduced SERCA1 Density at the Sarcoplasmic Reticulum Membrane
  rationale: >-
    The null mouse has severe diaphragm dysfunction, reduced transport and no detected compensatory expression
    changes. Human disease includes severe protein deficiency but usually a much milder clinical course. Species-specific
    diaphragm composition, residual function and alternative calcium-handling responses are plausible, nonexclusive
    contributors; none alone has been established as the explanation.
  proposed_experiments:
  - experiment_id: brody_hypomorphic_mouse
    name: Hypomorphic Atp2a1 mouse allele series matched to human residual activity
    description: >-
      Compare graded or conditional Atp2a1 loss with human residual protein and activity measurements, including
      diaphragm fibre composition and calcium clearance. This could distinguish neonatal complete-loss effects
      from variant- and species-dependent adaptation.
  evidence:
  - reference: PMID:12556521
    reference_title: Targeted disruption of the ATP2A1 gene encoding the sarco(endo)plasmic reticulum Ca2+ ATPase isoform 1 (SERCA1) impairs diaphragm function and is lethal in neonatal mice.
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: SERCA1-null mice had progressive cyanosis and gasping respiration and succumbed from respiratory failure shortly after birth
    explanation: Direct evidence for the model-specific lethal phenotype.
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Onset begins in childhood and there was no or only mild progression of symptoms over time.
    explanation: Human cohort contrast; does not establish that all patients lack respiratory involvement.
- discussion_id: brody_assay_specificity
  prompt: How specifically does reduced compound muscle calcium-ATPase activity identify ATP2A1-related Brody disease?
  kind: KNOWLEDGE_GAP
  status: OPEN
  attaches_to:
  - biochemical#Sarcoplasmic reticulum calcium ATPase activity
  rationale: The optimized assay separated four genetically confirmed patients from 28 healthy controls, but it includes SERCA1/SERCA2 and possible PMCA contributions. Other myopathies, muscle site, age, sex and disuse may alter results; clinical sensitivity and specificity require broader validation.
  evidence:
  - reference: PMID:41938373
    reference_title: Sarco/endoplasmatic reticulum calcium ATPase activity in healthy muscle and Brody disease.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Future research on SERCA activity in these subject groups is needed to determine the specificity of abnormal SERCA activity.
    explanation: The study explicitly identifies the disease-specificity gap.
differential_diagnoses:
- name: Brody syndrome without identified ATP2A1 variants
  description: Historically describes delayed relaxation and reduced SERCA activity without identified ATP2A1 variants. The 17-patient study found greater myalgia and daily-life impact than in gene-confirmed disease. This is not a genetically resolved subtype, and incomplete genetic testing or another cause of reduced activity must be considered.
  evidence:
  - reference: PMID:22704959
    reference_title: "Brody syndrome: a clinically heterogeneous entity distinct from Brody disease: a review of literature and a cross-sectional clinical study in 17 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: a distinction between Brody disease (with ATP2A1 mutations) and Brody syndrome (without ATP2A1 mutations) was proposed.
    explanation: Defines the scope boundary.
  - reference: PMID:22704959
    reference_title: "Brody syndrome: a clinically heterogeneous entity distinct from Brody disease: a review of literature and a cross-sectional clinical study in 17 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Patients with Brody syndrome more often report myalgia and experience a considerable impact on daily life.
    explanation: Clinical comparison in the historical syndrome study.
- name: Myotonia congenita and paramyotonia congenita
  description: These channelopathies commonly produce myotonic discharges, unlike the typical Brody pattern of electrically silent contractures. Clinical percussion myotonia alone does not settle the distinction.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
    snippet: myotonic disorders will typically demonstrate myotonic discharges at myography that are not seen in Brody disease
    explanation: Comparative diagnostic guidance; the qualifier typically avoids a universal statement about every myotonic presentation.
- name: McArdle disease
  description: Can also produce silent contractures. A second-wind phenomenon, persistently high creatine kinase and recurrent exercise-associated rhabdomyolysis favor McArdle disease, although rhabdomyolysis can also occur in Brody disease.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
    snippet: Silent contractures can also be found in McArdle disease (glycogen storage disease type V).
    explanation: Electrical silence is not uniquely diagnostic of Brody disease.
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
    snippet: McArdle disease typically presents with a second wind phenomenon, permanently high creatine kinase levels and episodes of rhabdomyolysis
    explanation: The broader phenotype helps distinguish the disorders.
- name: Rippling muscle disease
  description: Mechanically induced visible rippling or muscle mounding can also be electrically silent. Hereditary and immune-mediated forms differ from the ATP2A1-related relaxation defect.
  evidence:
  - reference: PMID:42124386
    reference_title: Muscle Stiffness due to Neuromuscular Hyperexcitability.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
    snippet: Rippling muscle disease (RMD) and Brody disease are extremely rare nonprogressive myopathies associated with electrical silence on needle EMG during muscle stiffness and delayed muscle relaxation
    explanation: The clinical review supports overlap in electrical silence; disease mechanisms and provocation patterns differ.
prevalence:
- population: Worldwide
  measure_type: UNKNOWN
  prevalence_class: ULTRA_RARE
  notes: Exact prevalence is unknown. Published cohort sizes and literature counts are ascertainment summaries and should not be divided by the world population or treated as a measured incidence.
  evidence:
  - reference: url:https://medlineplus.gov/genetics/condition/brody-myopathy/
    reference_title: "Brody myopathy: MedlinePlus Genetics"
    supports: SUPPORT
    evidence_source: OTHER
    directness: DIRECT
    quote_role: REVIEW_SYNTHESIS
    snippet: Brody myopathy is a rare condition, although its exact prevalence is unknown.
    explanation: Authoritative clinical summary does not supply a measured prevalence estimate.
experimental_models:
- name: HEK293 expression of human SERCA1 P789L and R819C
  experimental_model_type: CELL_LINE
  organism:
    preferred_term: Homo sapiens
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  cell_source: Heterologous HEK293 cells expressing human wild-type or mutant SERCA1
  publication: PMID:10914677
  description: P789L was readily expressed but lost most calcium transport because of reduced calcium affinity. R819C retained near-normal transport and was not supported as causative in the reported family. This assay separates expression from function; heterologous cells do not reproduce mature fast-twitch muscle physiology.
  modeled_mechanisms:
  - target: Intrinsic SERCA1 Calcium-Transport Defect
    description: Tests intrinsic transport impairment separately from protein abundance.
    relationship: PERTURBS
    fidelity: MODERATE
    evidence:
    - reference: PMID:10914677
      reference_title: The mutation of Pro789 to Leu reduces the activity of the fast-twitch skeletal muscle sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA1) and is associated with Brody disease.
      supports: SUPPORT
      evidence_source: IN_VITRO
      directness: DIRECT
      quote_role: PRIMARY_RESULT
      snippet: The Pro789 to Leu mutant was readily expressed in HEK-293 cells, but it demonstrated an almost complete loss of Ca2+ transport activity because of reduced Ca2+ affinity.
      explanation: Direct functional assay of a human disease-associated allele.
- name: Heterologous bovine SERCA1 instability and corrector assays
  experimental_model_type: CELL_LINE
  organism:
    preferred_term: Homo sapiens
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  cell_source: HEK293 or HeLa host cells expressing rabbit SERCA1 with R164H or bovine SERCA1 with G211V/G286V substitutions
  publication: PMID:36293223
  description: Transfected-cell assays measure mutant abundance, ER localization, ubiquitination, calcium transients and microsomal ATPase activity. G211V reduces abundance whereas G286V is largely benign. Proteasome inhibition and selected CFTR correctors rescue unstable variants. Host-cell species does not make these human pathogenic-variant experiments.
  modeled_mechanisms:
  - target: Proteasomal Degradation of Misfolded SERCA1
    description: Tests ubiquitination and protein rescue after proteasome inhibition.
    relationship: PERTURBS
    fidelity: MODERATE
    evidence:
    - reference: PMID:36293223
      reference_title: Differential Analysis of Gly211Val and Gly286Val Mutations Affecting Sarco(endo)plasmic Reticulum Ca(2+)-ATPase (SERCA1) in Congenital Pseudomyotonia Romagnola Cattle.
      supports: SUPPORT
      evidence_source: IN_VITRO
      directness: INDIRECT
      quote_role: PRIMARY_RESULT
      snippet: Inhibition of the UPS with MG132 led to an increase in the recovery of the polyubiquitinated G211V mutant
      explanation: Direct biochemical evidence for altered protein disposal in the transfected-cell system.
  - target: Reduced SERCA1 Density at the Sarcoplasmic Reticulum Membrane
    description: Corrector screening measures restoration of mutant protein abundance.
    relationship: PERTURBS
    fidelity: MODERATE
    evidence:
    - reference: PMID:41206505
      reference_title: "CFTR corrector C17 rescues defective SERCA1 in bovine pseudomyotonia: a potential therapy for Brody myopathy."
      supports: SUPPORT
      evidence_source: IN_VITRO
      directness: INDIRECT
      quote_role: PRIMARY_RESULT
      snippet: the incubation with CFTR correctors C17, C4 and C9, induced an increase in the expression level of SERCA1 mutant almost equivalent to that of MG132-treated cells
      explanation: Expression-level rescue does not alone establish clinical efficacy.
- name: Bovine pseudomyotonia muscle explants
  experimental_model_type: OTHER
  organism:
    preferred_term: Bos taurus
    term:
      id: NCBITaxon:9913
      label: Bos taurus
  cell_source: Fresh adult skeletal-muscle fibre bundles from affected cattle
  publication: PMID:41206505
  description: Muscle explants preserve differentiated diseased tissue for MG132 or corrector exposure. C17 and C4 increased mutant SERCA1 in SR-enriched fractions. Ex vivo response avoids whole-animal pharmacokinetics and therefore cannot establish systemic safety or functional benefit.
  modeled_mechanisms:
  - target: Reduced SERCA1 Density at the Sarcoplasmic Reticulum Membrane
    description: Tests pharmacological restoration of protein abundance in diseased muscle tissue.
    relationship: PERTURBS
    fidelity: MODERATE
    evidence:
    - reference: PMID:41206505
      reference_title: "CFTR corrector C17 rescues defective SERCA1 in bovine pseudomyotonia: a potential therapy for Brody myopathy."
      supports: SUPPORT
      evidence_source: IN_VITRO
      directness: INDIRECT
      quote_role: PRIMARY_RESULT
      snippet: the treatment with C17 or C4 correctors efficiently increased SERCA1 mutant expression
      explanation: Explant immunoblot readout supports protein rescue.
- name: Normal human primary muscle cultures for SERCA1 isoform characterization
  experimental_model_type: PRIMARY_CELL_CULTURE
  organism:
    preferred_term: Homo sapiens
    term:
      id: NCBITaxon:9606
      label: Homo sapiens
  cell_source: Primary cultures of normal human muscle; infant muscle examined for comparison
  publication: PMID:23911890
  description: Normal human cultured fibres predominantly express the neonatal SERCA1b isoform. This is an assay-development comparator rather than a demonstrated patient-derived Brody model, and isoform maturation must be considered when modeling adult SERCA1a disease.
  evidence:
  - reference: PMID:23911890
    reference_title: SERCA1 protein expression in muscle of patients with Brody disease and Brody syndrome and in cultured human muscle fibers.
    supports: SUPPORT
    evidence_source: IN_VITRO
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: We found that SERCA1b, the SERCA1 neonatal form, is the main protein isoform expressed in cultured human muscle fibers and infant muscle.
    explanation: Direct isoform result; the cultured cells were from normal human muscle.
progression:
- phase: Long-term course
  notes: Most patients have a relatively stable course, but strict lifelong nonprogression is not established. In the international cohort, 27 patients had follow-up averaging 9.3 years and three had more limited information. Seven of these 30 reported increased symptoms, while physicians observed no new weakness or atrophy. Retrospective ascertainment and the relatively young cohort limit conclusions about late adulthood.
  evidence:
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: Of these 30 patients, seven patients reported that symptoms had increased (23%).
    explanation: The denominator combines 27 patients with follow-up and three with limited progression information.
  - reference: PMID:32040565
    reference_title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    directness: DIRECT
    quote_role: PRIMARY_RESULT
    snippet: No development of weakness or atrophy was seen by physicians during follow-up physical examination.
    explanation: Reported symptom progression was not accompanied by newly observed weakness or atrophy in this cohort.
references:
- reference: PMID:10914677
  title: The mutation of Pro789 to Leu reduces the activity of the fast-twitch skeletal muscle sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA1) and is associated with Brody disease.
  findings:
  - statement: Human P789L impairs calcium affinity and transport despite preserved heterologous expression; R819C is not supported as causal.
- reference: PMID:12556521
  title: Targeted disruption of the ATP2A1 gene encoding the sarco(endo)plasmic reticulum Ca2+ ATPase isoform 1 (SERCA1) impairs diaphragm function and is lethal in neonatal mice.
  findings:
  - statement: Atp2a1-null mice show severe diaphragm dysfunction and neonatal lethality, limiting natural-history fidelity.
- reference: PMID:15469975
  title: "accordion, a zebrafish behavioral mutant, has a muscle relaxation defect due to a mutation in the ATPase Ca2+ pump SERCA1."
  findings:
  - statement: Accordion zebrafish connect SERCA1 dysfunction to impaired muscle relaxation.
- reference: PMID:15581877
  title: A mutation in serca underlies motility dysfunction in accordion zebrafish.
  findings:
  - statement: Zebrafish calcium-transient and contraction experiments distinguish muscle calcium clearance from neural output.
- reference: PMID:18786632
  title: "Identification of a missense mutation in the bovine ATP2A1 gene in congenital pseudomyotonia of Chianina cattle: an animal model of human Brody disease."
  findings:
  - statement: Chianina cattle ATP2A1 R164H founder model with reduced muscle calcium-ATPase activity.
- reference: PMID:20142766
  title: "Brody disease: insights into biochemical features of SERCA1 and identification of a novel mutation."
  findings:
  - statement: Affected siblings show SR ultrastructural remodeling and discordance between immunostaining and quantitative protein measurement.
- reference: PMID:20547455
  title: "Pseudomyotonia, a muscle function disorder associated with an inherited ATP2A1 (SERCA1) defect in a Dutch Improved Red and White cross-breed calf."
  findings:
  - statement: Dutch calf R559C disease model with low SERCA activity and absent electrical myotonia.
- reference: PMID:22704959
  title: "Brody syndrome: a clinically heterogeneous entity distinct from Brody disease: a review of literature and a cross-sectional clinical study in 17 patients."
  findings:
  - statement: ATP2A1-negative Brody syndrome is clinically heterogeneous and distinct from genetically defined Brody disease.
- reference: PMID:23046865
  title: Pseudomyotonia in Romagnola cattle caused by novel ATP2A1 mutations.
  findings:
  - statement: Romagnola cattle provide ATP2A1 genotype, protein and ATPase evidence; later work resolves the pathogenic G211V and benign G286V contributions.
- reference: PMID:23911890
  title: SERCA1 protein expression in muscle of patients with Brody disease and Brody syndrome and in cultured human muscle fibers.
  findings:
  - statement: SERCA1 assay-method effects and neonatal SERCA1b predominance in normal human muscle cultures.
- reference: PMID:25288803
  title: Inhibition of ubiquitin proteasome system rescues the defective sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA1) protein causing Chianina cattle pseudomyotonia.
  findings:
  - statement: MG132 rescues unstable bovine mutant SERCA1 in experimental systems; clinical efficacy is untested.
- reference: PMID:25614869
  title: Exome analysis identifies Brody myopathy in a family diagnosed with malignant hyperthermia susceptibility.
  findings:
  - statement: Human family with severe SERCA1 reduction and increased SERCA2 in the studied biopsy; compensation remains an interpretation.
- reference: PMID:26482047
  title: Fast-twitch skeletal muscle fiber adaptation to SERCA1 deficiency in a Dutch Improved Red and White calf pseudomyotonia case.
  findings:
  - statement: A mildly affected R559C calf has increased PMCA and mitochondrial markers without SERCA2 upregulation.
- reference: PMID:32040565
  title: "Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients."
  findings:
  - statement: Forty-patient international clinical, genetic and biopsy cohort, including natural history, perioperative precautions and limited symptomatic drug responses.
- reference: PMID:36293223
  title: Differential Analysis of Gly211Val and Gly286Val Mutations Affecting Sarco(endo)plasmic Reticulum Ca(2+)-ATPase (SERCA1) in Congenital Pseudomyotonia Romagnola Cattle.
  findings:
  - statement: Bovine G211V undergoes accelerated proteasomal disposal while surviving pump molecules retain activity; G286V is largely benign.
- reference: PMID:37332993
  title: "Case report: Clinical and molecular characterization of two siblings affected by Brody myopathy."
  findings:
  - statement: Two siblings with childhood stiffness, falls and compound heterozygous variants; RNA confirms in-frame exon skipping.
- reference: PMID:38125752
  title: "Case report: Revealing the rare-a Brody Disease patient from Turkey expanding the phenotype."
  findings:
  - statement: Adult case broadens reported clinical variability; variant interpretation and possible exotropia association remain limited by lack of functional confirmation.
- reference: PMID:38373275
  title: "Brody Disease, an Early-Onset Myopathy With Delayed Relaxation and Abnormal Gait: A Case Series of 9 Children."
  findings:
  - statement: Nine children demonstrate early abnormal gait and running difficulty with delayed recognition of the relaxation defect.
- reference: PMID:39273176
  title: The Accordion Zebrafish tq206 Mutant in the Assessment of a Novel Pharmaceutical Approach to Brody Myopathy.
  findings:
  - statement: C17 does not rescue key homozygous S766F zebrafish outcomes; this model differs from unstable-protein cattle variants.
- reference: PMID:41206505
  title: "CFTR corrector C17 rescues defective SERCA1 in bovine pseudomyotonia: a potential therapy for Brody myopathy."
  findings:
  - statement: CFTR corrector screening, muscle-explant experiments and local C17 injections in two calves support selected mutant-protein rescue without demonstrating human efficacy or systemic safety.
- reference: PMID:41926432
  title: "Rare Brody myopathy: A case report."
  findings:
  - statement: Single rhabdomyolysis case reports symptomatic improvement with dantrolene.
- reference: PMID:41938373
  title: Sarco/endoplasmatic reticulum calcium ATPase activity in healthy muscle and Brody disease.
  findings:
  - statement: Muscle SERCA assay compares 28 controls with four Brody cases; the reference limit and excellent within-sample discrimination require broader validation.
- reference: PMID:42124386
  title: Muscle Stiffness due to Neuromuscular Hyperexcitability.
  findings:
  - statement: Clinical review distinguishes electrically silent Brody contractures from other causes of muscle stiffness.
- reference: PMID:8841193
  title: "Mutations in the gene-encoding SERCA1, the fast-twitch skeletal muscle sarcoplasmic reticulum Ca2+ ATPase, are associated with Brody disease."
  findings:
  - statement: Founding evidence for autosomal recessive ATP2A1-related Brody disease.
- reference: url:https://medlineplus.gov/genetics/condition/brody-myopathy/
  title: "Brody myopathy: MedlinePlus Genetics"
  findings:
  - statement: Clinical summary of characteristic stiffness, recessive inheritance and unknown prevalence.

📚

References & Deep Research

References

PMID:10914677

The mutation of Pro789 to Leu reduces the activity of the fast-twitch skeletal muscle sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA1) and is associated with Brody disease.

1 finding

Human P789L impairs calcium affinity and transport despite preserved heterologous expression; R819C is not supported as causal.

PMID:12556521

Targeted disruption of the ATP2A1 gene encoding the sarco(endo)plasmic reticulum Ca2+ ATPase isoform 1 (SERCA1) impairs diaphragm function and is lethal in neonatal mice.

1 finding

Atp2a1-null mice show severe diaphragm dysfunction and neonatal lethality, limiting natural-history fidelity.

PMID:15469975

accordion, a zebrafish behavioral mutant, has a muscle relaxation defect due to a mutation in the ATPase Ca2+ pump SERCA1.

1 finding

Accordion zebrafish connect SERCA1 dysfunction to impaired muscle relaxation.

PMID:15581877

A mutation in serca underlies motility dysfunction in accordion zebrafish.

1 finding

Zebrafish calcium-transient and contraction experiments distinguish muscle calcium clearance from neural output.

PMID:18786632

Identification of a missense mutation in the bovine ATP2A1 gene in congenital pseudomyotonia of Chianina cattle: an animal model of human Brody disease.

1 finding

Chianina cattle ATP2A1 R164H founder model with reduced muscle calcium-ATPase activity.

PMID:20142766

Brody disease: insights into biochemical features of SERCA1 and identification of a novel mutation.

1 finding

Affected siblings show SR ultrastructural remodeling and discordance between immunostaining and quantitative protein measurement.

PMID:20547455

Pseudomyotonia, a muscle function disorder associated with an inherited ATP2A1 (SERCA1) defect in a Dutch Improved Red and White cross-breed calf.

1 finding

Dutch calf R559C disease model with low SERCA activity and absent electrical myotonia.

PMID:22704959

Brody syndrome: a clinically heterogeneous entity distinct from Brody disease: a review of literature and a cross-sectional clinical study in 17 patients.

1 finding

ATP2A1-negative Brody syndrome is clinically heterogeneous and distinct from genetically defined Brody disease.

PMID:23046865

Pseudomyotonia in Romagnola cattle caused by novel ATP2A1 mutations.

1 finding

Romagnola cattle provide ATP2A1 genotype, protein and ATPase evidence; later work resolves the pathogenic G211V and benign G286V contributions.

PMID:23911890

SERCA1 protein expression in muscle of patients with Brody disease and Brody syndrome and in cultured human muscle fibers.

1 finding

SERCA1 assay-method effects and neonatal SERCA1b predominance in normal human muscle cultures.

PMID:25288803

Inhibition of ubiquitin proteasome system rescues the defective sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA1) protein causing Chianina cattle pseudomyotonia.

1 finding

MG132 rescues unstable bovine mutant SERCA1 in experimental systems; clinical efficacy is untested.

PMID:25614869

Exome analysis identifies Brody myopathy in a family diagnosed with malignant hyperthermia susceptibility.

1 finding

Human family with severe SERCA1 reduction and increased SERCA2 in the studied biopsy; compensation remains an interpretation.

PMID:26482047

Fast-twitch skeletal muscle fiber adaptation to SERCA1 deficiency in a Dutch Improved Red and White calf pseudomyotonia case.

1 finding

A mildly affected R559C calf has increased PMCA and mitochondrial markers without SERCA2 upregulation.

PMID:32040565

Clinical, morphological and genetic characterization of Brody disease: an international study of 40 patients.

1 finding

Forty-patient international clinical, genetic and biopsy cohort, including natural history, perioperative precautions and limited symptomatic drug responses.

PMID:36293223

Differential Analysis of Gly211Val and Gly286Val Mutations Affecting Sarco(endo)plasmic Reticulum Ca(2+)-ATPase (SERCA1) in Congenital Pseudomyotonia Romagnola Cattle.

1 finding

Bovine G211V undergoes accelerated proteasomal disposal while surviving pump molecules retain activity; G286V is largely benign.

PMID:37332993

Case report: Clinical and molecular characterization of two siblings affected by Brody myopathy.

1 finding

Two siblings with childhood stiffness, falls and compound heterozygous variants; RNA confirms in-frame exon skipping.

PMID:38125752

Case report: Revealing the rare-a Brody Disease patient from Turkey expanding the phenotype.

1 finding

Adult case broadens reported clinical variability; variant interpretation and possible exotropia association remain limited by lack of functional confirmation.

PMID:38373275

Brody Disease, an Early-Onset Myopathy With Delayed Relaxation and Abnormal Gait: A Case Series of 9 Children.

1 finding

Nine children demonstrate early abnormal gait and running difficulty with delayed recognition of the relaxation defect.

PMID:39273176

The Accordion Zebrafish tq206 Mutant in the Assessment of a Novel Pharmaceutical Approach to Brody Myopathy.

1 finding

C17 does not rescue key homozygous S766F zebrafish outcomes; this model differs from unstable-protein cattle variants.

PMID:41206505

CFTR corrector C17 rescues defective SERCA1 in bovine pseudomyotonia: a potential therapy for Brody myopathy.

1 finding

CFTR corrector screening, muscle-explant experiments and local C17 injections in two calves support selected mutant-protein rescue without demonstrating human efficacy or systemic safety.

PMID:41926432

Rare Brody myopathy: A case report.

1 finding

Single rhabdomyolysis case reports symptomatic improvement with dantrolene.

PMID:41938373

Sarco/endoplasmatic reticulum calcium ATPase activity in healthy muscle and Brody disease.

1 finding

Muscle SERCA assay compares 28 controls with four Brody cases; the reference limit and excellent within-sample discrimination require broader validation.

PMID:42124386

Muscle Stiffness due to Neuromuscular Hyperexcitability.

1 finding

Clinical review distinguishes electrically silent Brody contractures from other causes of muscle stiffness.

PMID:8841193

Mutations in the gene-encoding SERCA1, the fast-twitch skeletal muscle sarcoplasmic reticulum Ca2+ ATPase, are associated with Brody disease.

1 finding

Founding evidence for autosomal recessive ATP2A1-related Brody disease.

url:https://medlineplus.gov/genetics/condition/brody-myopathy/

Brody myopathy: MedlinePlus Genetics

1 finding

Clinical summary of characteristic stiffness, recessive inheritance and unknown prevalence.

Deep Research

Deep research results are used as seeds for research; they do not undergo the same validation as the main records and may contain errors. How we use deep research.

Evaluations and curation notes (2)

Review Brody myopathy mechanisms, clinical spectrum, diagnostics and experimental rescue evidence · 2026-10-01T10:59:06Z · View source

Reviewed the existing entry and matching deep-research report against cached abstracts and available full text, including the international clinical cohort, human intrinsic pump-defect study, 2024 pediatric series, 2026 quantitative SERCA assay, bovine protein-rescue studies and negative zebrafish corrector results. Distinguished loss of pump abundance from intrinsic transport dysfunction, qualified proposed compensation, corrected phenotype denominators and malignant-hyperthermia interpretation, added childhood gait problems and rhabdomyolysis, and separated clinical care from experimental pharmacology. Recovered genuine 2008 and 2026 references previously dismissed in research notes, excluded unrelated gene-negative and animal-only clinical claims, and documented model limitations. GeneReviews/StatPearls searches found no dedicated chapter; trial search found no disease-specific interventional study.

Create: Brody Myopathy (MONDO:0010977) · 2026-08-16T14:50:15Z · View source

New entry curated from a claude_code deep-research report. Eight pathophysiology nodes running biallelic ATP2A1 loss of function through two allelic routes (truncating/splice, and missense degraded by the ubiquitin-proteasome system before reaching the SR membrane) to reduced SERCA1 density, impaired calcium reuptake, prolonged cytosolic calcium, and the electrically silent contracture that is the diagnostic discriminator. Type II fibre selectivity modelled as its own node because it explains the distribution (SERCA1 is the fast-twitch isoform; heart runs SERCA2a and is uninvolved). The compensation branch is modelled rather than left as prose because it is load-bearing for prognosis, and carries two competing mechanistic_hypotheses: pmca_extrusion_compensation (EMERGING, bovine evidence) and serca2_isoform_compensation (ALTERNATIVE, one supporting human family, refuted by both the 40-patient cohort and the bovine model). A HUMAN_MODEL_MISMATCH discussion records that the Atp2a1-null mouse dies at birth of diaphragm failure while humans have no respiratory involvement, with a hypomorphic allele series proposed to separate species biology from allele severity. Three animal models including the Atp2a1-null mouse as FAILS_TO_RECAPITULATE with required limitations and evidence. Scope: Brody DISEASE (ATP2A1-confirmed); Brody SYNDROME (gene-negative) recorded as the primary differential with its own citation. Two PMIDs cited by the DR report (PMID:41938373, PMID:18786632) were flagged unresolved by the report's own reference validation and are NOT curated; the omission and reason are recorded in entry notes. HP:0100301 was initially used for delayed muscle relaxation and is wrong (it is Muscle fiber tubular inclusions); no HPO term fits that sign, and binding it to Myotonia would encode the exact misdiagnosis the entry exists to prevent, so it is carried as free text. Validated: just validate passed (schema + terms + references); count-verified-snippets 39/39; check_folded_hyphens OK; check-title-snippets OK.

Claude Code ▸

Brody Myopathy — Comprehensive Disease Research Report

claude-haiku-4-5-20251001, claude-opus-5[1m] 32 citations 2026-08-16T10:18:58.798689

Brody Myopathy — Comprehensive Disease Research Report

Prepared: 2026-08-16 · Target entity: Brody myopathy / Brody disease · MONDO:0010977 (verified via OLS4)

How to read the citations here. Quotes marked [verbatim] were pulled character-for-character from the PubMed abstract record via NCBI E-utilities and are safe to use as evidence snippet: values. Anything marked [full-text derived] came from reading article body text through a summarizing fetch — those numbers are leads, and need re-verification against the source before they get curated with a snippet. Ontology IDs marked [OAK-verified] were checked against local sqlite:obo:* adapters in this session; everything else is a suggestion to check.

1. Disease Information

What it is

Brody myopathy is an ultra-rare, autosomal recessive skeletal muscle disorder in which the calcium pump that resets fast-twitch muscle after a contraction is broken. Think of a sink with a slow drain: the contraction fills the cytoplasm with calcium just fine, but emptying it back into the sarcoplasmic reticulum takes far too long. Clinically that reads as exercise-induced stiffness and delayed relaxation — a cramp-like tightening that looks exactly like myotonia but is electrically silent on needle EMG. That silence is the diagnostic tell.

It is caused by biallelic pathogenic variants in ATP2A1, encoding SERCA1 (sarco/endoplasmic reticulum Ca²⁺-ATPase, isoform 1), the pump that dominates type II (fast-twitch) fibers.

[verbatim] "Brody disease is an autosomal recessive myopathy characterized by exercise-induced muscle stiffness due to mutations in the ATP2A1 gene." — Molenaar et al., Brain 2020 (PMID:32040565)

[verbatim] "Brody disease is a rare inherited disorder of skeletal muscle function. Symptoms include exercise-induced impairment of skeletal muscle relaxation, stiffness and cramps. Ca2+ uptake and Ca2+ ATPase activities are reduced in the sarcoplasmic reticulum…" — Odermatt et al., Nature Genetics 1996 (PMID:8841193)

First description

Irwin A. Brody, NEJM 1969;281(4):187–192, "Muscle contracture induced by exercise. A syndrome attributable to decreased relaxing factor" (PMID:4239835). No structured abstract exists on this record — do not attempt to snippet-validate against it. The gene link followed 27 years later (Odermatt 1996).

Key identifiers

Resource	Identifier
MONDO	MONDO:0010977 — "Brody myopathy" (OLS4-verified)
OMIM (disease)	601003 — BRODY DISEASE; BROD
OMIM (gene)	108730 — ATP2A1
Orphanet	ORPHA:53347 — Brody myopathy
HGNC	hgnc:811 — ATP2A1 [OAK-verified]
UMLS	C1832918 (per NIH GTR conditions page)
ICD-10	G71.2 / G72.8 range (metabolic-myopathy bucket; no dedicated code) — verify against the ICD release you target
ICD-11	8C70.Y / 8C7Y range (other specified myopathies) — verify
MeSH	No dedicated descriptor; indexed under Muscular Diseases / Muscle Relaxation

Synonyms and naming

Brody disease (BROD)
Brody myopathy
SERCA1 deficiency
Sarcoplasmic reticulum Ca²⁺-ATPase deficiency
ATP2A1-related myopathy

One naming distinction really matters for curation. The literature separates:

Brody disease — reduced SERCA activity with identified biallelic ATP2A1 variants.
Brody syndrome — the same clinical/biochemical picture without ATP2A1 variants; genetically unsolved.

[verbatim, partial] "Brody disease is a rare inherited myopathy due to reduced sarcoplasmic reticulum Ca(2+) ATPase (SERCA)1 activity." … "Brody disease presents with an onset in the 1st decade, a generalized pattern of muscle stiffness" … "Patients with Brody syndrome more often report myalgia and experience a considerable impact on daily life." — Voermans et al., Neuromuscul Disord 2012 (PMID:22704959), cross-sectional study of 17 Brody syndrome patients

MONDO folds "Brody disease" in as a synonym of MONDO:0010977. If you want the syndrome/disease split represented, do it with a subtype or a lump/split note rather than a second MONDO term.

Data provenance

Everything below is disease-level aggregated knowledge — case reports, one 40-patient international cohort, and one 17-patient cross-sectional study. There is no registry, no EHR-derived cohort, and no natural-history study with structured longitudinal data. Curate accordingly: frequencies come from n≈40, not from a population.

2. Etiology

Primary cause

Biallelic (homozygous or compound heterozygous) loss-of-function variants in ATP2A1 (16p11.2; older literature maps it to 16p12.1-12.2). Purely Mendelian — no infectious, environmental, or autoimmune contribution to causation.

Two mechanistic flavors of "loss of function," and they matter therapeutically:

Quantitative loss — nonsense, frameshift, splice, large deletion → little or no SERCA1 protein made.
Qualitative/folding loss — missense → protein is often catalytically competent but misfolded, recognized by ER quality control, ubiquitinated, and destroyed before it reaches the SR membrane. This is the CFTR-ΔF508 playbook running in a different gene, and it's the entire basis for the corrector-drug strategy in §12.

[verbatim] "Most mutations generate proteins corrupted in proper folding that although catalytically active, were ubiquitinated and prematurely degraded by the ubiquitin-proteasome system, thus sharing with Cystic Fibrosis the same pathogenetic mechanism." — Sacchetto group, Hum Mol Genet 2025 (PMID:41206505)

Genetic risk factors

Causal: biallelic ATP2A1 variants. Heterozygous carriers are clinically unaffected.
Not causal: heterozygous ATP2A1 variants alone. Odermatt 2000 explicitly disproved one candidate this way.

[verbatim] "In a fourth family, the heterozygous substitution of T for C2455, mutating Arg819 to Cys, was identified. This mutation was also readily expressed in HEK-293 cells and shown to have near normal Ca2+ transport activity, indicating that it is not causal for Brody disease." — Odermatt et al., Hum Genet 2000 (PMID:10914677)

Consanguinity raises risk, as for any AR disorder; the 2023 Turkish case was homozygous, consistent with that.
No modifier genes have been identified. Genotype–phenotype correlation is reported as absent (see §4).

Environmental risk / trigger factors

There is a clean distinction here that a knowledge base should preserve: nothing environmental causes Brody myopathy, but several things unmask or worsen it. Triggers, not etiology:

Trigger	Effect	Evidence
Physical exertion (even mild)	Elicits stiffness/delayed relaxation — the defining trigger	PMID:32040565, PMID:39273176
Cold exposure	Symptom exacerbation, reported in ~72% of the cohort	PMID:32040565 [full-text derived]
Volatile anesthetics + succinylcholine	Precipitate malignant-hyperthermia-like episodes	PMID:32040565, PMID:25614869
Repetitive contraction	The physical-exam provocation maneuver	PMID:32040565

Suggested ECTO grounding: exposure to cold temperature and exposure to anesthetic agent concepts — verify CURIEs with OAK before binding; I did not verify ECTO terms this session.

Protective factors

None documented. No protective allele, dietary factor, or lifestyle exposure has been reported.
Pacing, warm environments, and avoidance of maximal exertion are symptom-avoidance strategies, not protective factors in the epidemiological sense.
There is no "second wind" phenomenon (that's McArdle disease) — a useful negative for differential diagnosis.

Gene–environment interaction

One real, clinically consequential interaction: genotype (biallelic ATP2A1 LoF) × anesthetic exposure → MH-like crisis. The proposed convergence is shared elevated myoplasmic calcium.

[verbatim, partial] Sambuughin et al. note that "elevated myoplasmic Ca(2+) content" is common to both conditions, explaining the secondary malignant hyperthermia diagnosis alongside the primary Brody myopathy. — Mol Genet Genomic Med 2014 (PMID:25614869)

3. Phenotypes

HPO annotations currently attached to OMIM:601003

Retrieved live from the HPO annotation service. Note the many 0/N entries — these are curated exclusions, and they're arguably the most diagnostically valuable part of the profile:

HP ID	Term	Annotated frequency
HP:0008967	Exercise-induced muscle stiffness	10/10
HP:0011463	Childhood onset	5/5
HP:0003710	Exercise-induced muscle cramps	1/1
HP:0002047	Malignant hyperthermia	1/1
HP:0001270	Motor delay	1/1
HP:0003623	Neonatal onset	1/1
HP:0009046	Difficulty running	1/5
HP:0000007	Autosomal recessive inheritance	—
HP:0002486	Myotonia	0/5 (excluded)
HP:0100284	EMG: myotonic discharges	0/5 (excluded)
HP:0010548	Percussion myotonia	0/10 (excluded)
HP:0001324	Muscle weakness	0/5 (excluded)
HP:0003326	Myalgia	0/5
HP:0002411	Myokymia	0/5 (excluded)
HP:0002380	Fasciculations	0/5 (excluded)
HP:0001371	Flexion contracture	0/5 (excluded)
HP:0003712	Skeletal muscle hypertrophy	0/5
HP:0031826	Abnormal reflex	0/5
HP:0003474	Somatic sensory dysfunction	0/5

All HP IDs above independently [OAK-verified] against sqlite:obo:hp except where the HPO service supplied them directly.

Clinical features with cohort frequencies

From the 40-patient international cohort (Molenaar 2020, PMID:32040565). [full-text derived — re-verify before snippet-curation]

Feature	Frequency	Suggested HP term
Exercise-induced muscle stiffness (limbs)	40/40 (100%)	HP:0008967
Lower-limb involvement	38/38 (100%)	HP:0008967
Upper-limb involvement	33/38 (87%)	HP:0008967
Cold sensitivity / cold-induced worsening	25/36 (72%)	— (qualifier, not a term)
Athletic build (paradoxical)	20/30 (67%)	HP:0003712 (approximate)
Eyelid stiffness	24/38 (63%)	HP:0008967 + UBERON:0001711 site
Stiffness at exercise onset	19/30 (63%)	—
Myalgia	20/34 (59%)	HP:0003326 / HP:0003738
Muscle cramps	18/34 (52%)	HP:0003710
Reported muscle weakness	11/35 (31%)	HP:0001324 — often misperceived stiffness
MH-like episodes	4/40 (10%)	HP:0002047
Clinical muscle atrophy	0/33 (0%)	(excluded)

The abstract-level statements are safely quotable:

[verbatim] "This observational study shows that the main feature of Brody disease is an exercise-induced muscle stiffness of the limbs, and often of the eyelids. Onset begins in childhood and there was no or only mild progression of symptoms over time. Four patients had episodes resembling malignant hyperthermia. The key finding at physical examination was delayed relaxation after repetitive contractions. Additionally, no atrophy was seen, muscle strength was generally preserved, and some patients had a remarkable athletic build." — PMID:32040565

The eyelid involvement isn't a curiosity — it's mechanistically informative. Orbicularis oculi (UBERON:0001578 [OAK-verified]) is a fast-twitch-rich muscle, so it's exactly where a SERCA1-specific defect should show up first.

Phenotype characteristics

Age of onset: first decade in the large majority. Mean reported symptom onset 19.2 ± 15.0 yr with 38/40 in childhood [full-text derived] — the mean is skewed by late-recognized cases; the modal onset is childhood. The 2023 Turkish case pushed onset into the second decade (age 14–15).
Severity: mild to moderate. Strength preserved. Most patients function independently.
Progression: essentially non-progressive or minimally progressive. This is a load-bearing fact for prognosis.
Course: episodic/exertional — stiffness appears with activity and resolves with a few minutes of rest.
Duration: lifelong.

Laboratory phenotype

Creatine kinase (HP:0003236 [OAK-verified]): normal or mildly elevated. Range 50–1,300 IU/L, roughly half normal and half mildly-to-moderately raised [full-text derived].
SERCA activity in muscle homogenate: markedly reduced — now with proper reference values, see §10.
Rhabdomyolysis (HP:0003201 [OAK-verified]): rare. A 2026 case presented with exercise-induced rhabdomyolysis as the index event (PMID:41926432) — this genuinely expands the recognized presentation.

Quality-of-life impact

Thin evidence, honestly. The 2020 cohort used a Modified Rankin Scale, with 13/23 (57%) at "slight disability but able to look after own affairs" [full-text derived]. No EQ-5D, SF-36, or PROMIS data exist for this disease. Notably, Voermans 2012 reports that Brody syndrome patients (the gene-negative group) report more myalgia and greater daily-life impact than Brody disease patients — a genuine, quotable contrast.

4. Genetic / Molecular Information

Causal gene

ATP2A1 — ATPase sarcoplasmic/endoplasmic reticulum Ca²⁺ transporting 1

HGNC: hgnc:811 [OAK-verified] (note repo convention: lowercase hgnc:)
OMIM gene: 108730
Locus: 16p11.2
Reference transcript commonly used in reports: NM_004320.4
Protein: SERCA1a, ~994 aa, ~110 kDa P-type ATPase
UniProt: O14983 (SERCA1 human) — verify before binding

Splice isoforms. ATP2A1 makes two developmentally regulated isoforms by alternative splicing at the 3′ end: SERCA1a (adult; stop codon in exon 22) and SERCA1b (neonatal; skips exon 22, stop in exon 23). SERCA1a is >99% of SERCA1 in adult skeletal muscle. This matters for in-vitro work — Guglielmi 2013 found the neonatal SERCA1b isoform predominates in cultured human myotubes and in infant muscle, which limits how well cultured fibers model the adult defect.

Pathogenic variant landscape

Variant classes seen in Brody disease (all reported): nonsense, frameshift (deletions and insertions/duplications), canonical splice-site, in-frame single-codon deletions, missense, and large rearrangements including whole-gene deletion.

From the 40-patient cohort, 33 distinct mutations [full-text derived]:

Class	Count
Missense	11
Frameshift	7
Nonsense (stop)	6
Splice-site	4
In-frame single-codon deletion	3
Large rearrangement (exon 9 del; whole-gene del)	2

Recurrent variants noted across unrelated families [full-text derived]: p.Leu67del, c.2464dup, exon 9 deletion, p.Arg560Cys. None constitutes an established founder allele.

Individually characterized variants worth curating:

Variant	Consequence	Source
Intron 3 splice-donor site variant	Splice defect	PMID:8841193 [verbatim]
Two premature stop codons (two families)	Truncated SERCA1, essential domains deleted	PMID:8841193 [verbatim]
c.2366C>T, p.Pro789Leu (homozygous)	Expressed in HEK-293 but "almost complete loss of Ca²⁺ transport activity because of reduced Ca²⁺ affinity"	PMID:10914677 [verbatim]
c.2455C>T, p.Arg819Cys (het)	Near-normal transport — NOT causal	PMID:10914677 [verbatim]
Two novel in-frame deletions (siblings)	Reduced SERCA1 protein amount, normal IHC pattern	PMID:20142766 [verbatim]
p.Ile235Asn + p.Glu982Lys (compound het)	Absent SERCA1, elevated SERCA2; family carried an MH-susceptibility diagnosis	PMID:25614869
Two novel heterozygous exon 3 variants	—	PMID:23911890 [verbatim]
c.2464delC (frameshift) + c.324+1G>A (novel splice)	Compound het in two siblings	PMID:37332993 [verbatim]
c.428G>A, p.Arg143Gln (homozygous, NM_004320.4)	Very mild, second-decade onset, Turkish patient	PMID:38125752 [verbatim]

[verbatim] "Here, we report a Turkish Brody Disease patient with a homozygous c.428G>A p.Arg143Gln (NM_004320.4) missense mutation in the ATP2A1." — PMID:38125752

Variant classification / population frequency — honest gaps:

ClinVar: a query on ATP2A1[gene] returns 1,113 variation records total; restricting to pathogenic/likely-pathogenic returns 268. That P/LP number is almost certainly inflated by multi-gene CNV records, because ATP2A1 sits inside the recurrent distal 16p11.2 BP2–BP3 ~220 kb deletion (chr16:28.73–28.95 Mb, ~9 genes including SH2B1; OMIM 613444), which is curated as pathogenic for obesity/developmental delay. Do not curate 268 as "268 pathogenic ATP2A1 variants." Re-derive with an explicit single-gene filter.
gnomAD constraint (pLI, LOEUF, o/e): I was unable to retrieve these — the gnomAD browser is a JS app and its API needs POST. Flagging as not-retrieved rather than guessing. What is clinically established: heterozygous carriers are asymptomatic, so ATP2A1 is not haploinsufficient in the disease-causing sense.
Carrier frequency: not established anywhere I could find. Given ~47 patients ever reported, it has never been measured directly.

Somatic vs germline

Entirely germline. No somatic ATP2A1 disease has been described. (Incidental note: ATP2A1 shows up in cancer expression literature, but that's not a somatic disease mechanism relevant here.)

Functional consequences

Loss of function in all pathogenic cases. Two sub-mechanisms: reduced protein quantity (truncating) and reduced protein stability/trafficking despite retained catalysis (missense; see §6).
No gain-of-function or dominant-negative mechanism reported.

Modifier genes, epigenetics, chromosomal abnormalities

Modifier genes: none identified.
Genotype–phenotype: explicitly reported as absent — "No gradation in severity could be demonstrated in clinical presentation… leading to no particular phenotype-to-genotype correlations." [full-text derived, PMID:32040565]
Epigenetics: no DNA methylation, histone, or chromatin studies exist for Brody myopathy. Genuine blank.
Chromosomal abnormalities: whole-gene ATP2A1 deletion has been reported as one allele. The distal 16p11.2 BP2–BP3 deletion removes one ATP2A1 copy but is not reported to cause Brody myopathy on its own — it would need a second-hit point variant in trans. This is a plausible-but-unreported compound-heterozygous mechanism worth flagging as a knowledge gap.

5. Environmental Information

Short section, and it should be. Brody myopathy is Mendelian, full stop.

Environmental factors: no toxin, radiation, pollutant, or occupational exposure contributes to causation. Cold and exertion are symptom triggers, not causes.
Lifestyle factors: no dietary, smoking, or alcohol association. Athletic training is neither causal nor protective; several patients are notably athletic despite the disease.
Infectious agents: none. Not applicable.
Iatrogenic exposure worth modeling: volatile anesthetics and depolarizing muscle relaxants (succinylcholine, CHEBI:45652 [OAK-verified]) as MH-crisis triggers. This is the one exposure that belongs in an environmental: block with influences_mechanisms.

6. Mechanism / Pathophysiology

Here's the causal chain, laid out for a pathograph.

The normal biology it breaks

SERCA1 is a P-type ATPase with three cytoplasmic domains (A/actuator, N/nucleotide-binding, P/phosphorylation) and ten transmembrane helices carrying two Ca²⁺-binding sites. It runs a Post-Albers E1/E2 cycle, pumping 2 Ca²⁺ into the SR lumen per ATP hydrolyzed against a countertransport of protons. In fast-twitch fibers it is the overwhelmingly dominant route by which cytosolic calcium is cleared after a contraction — i.e., it is the relaxation machinery. It is tonically restrained by small regulatory peptides (sarcolipin, myoregulin); phospholamban does the equivalent job for the SERCA2a isoform in heart and slow muscle. Structural reference: Toyoshima's rabbit SERCA1a structure (PDB 1SU4) — verify PDB before binding.

Causal chain, upstream → downstream

Step 1 (MOLECULAR). Biallelic ATP2A1 LoF variants. → Two routes: - 1a. Truncating/splice/deletion → little or no SERCA1 protein synthesized. - 1b. Missense → protein folds badly, is ubiquitinated, and is stripped out by the ubiquitin–proteasome system before reaching the SR membrane, despite retaining catalytic activity.

[verbatim, partial] Bianchini et al. showed the mutation "impairs protein folding rather than catalytic function," and that proteasome inhibition restores "the same ability of wild type to maintain Ca(2+) homeostasis within cells." — J Biol Chem 2014 (PMID:25288803)

Step 2 (MOLECULAR). Reduced SERCA1 protein at the SR membrane → reduced SR Ca²⁺-ATPase activity. Measured reduction: 50–80% of control activity [full-text derived], and now quantified against proper reference values:

[verbatim] "With the optimized assay, SERCA activity was assessed in muscle samples from healthy controls (n = 28) and patients with Brody disease (n = 4)… demonstrate marked decreased SERCA activity in Brody disease muscle samples (30.0 ± 4.2 mU/mg protein) compared to controls (86.7 ± 25.1 mU/mg protein)." — Biochem Biophys Rep 2026 (PMID:41938373)

Step 3 (CELLULAR). Impaired Ca²⁺ re-uptake into the SR → prolonged elevation of cytosolic free Ca²⁺ after each contraction, i.e. a slow calcium-transient decay. Directly imaged in the zebrafish model:

[verbatim] "In vivo imaging of muscle Ca2+ transients revealed that cytosolic Ca2+ decay was significantly slower in acc muscle. Thus, it appears that the mutant behavior is caused by a muscle relaxation defect due to the impairment of Ca2+ re-uptake." — Hirata et al., Development 2004 (PMID:15469975)

Step 4 (CELLULAR/TISSUE). Sustained cytosolic Ca²⁺ keeps troponin C saturated and cross-bridges cycling → electrically silent contracture. The key word is silent: the sarcolemma isn't misbehaving, so needle EMG records nothing during the stiffness. That's what separates it from every myotonia on the differential.

Step 5 (TISSUE). Selective type II (fast-twitch) fiber involvement, because SERCA1 is the fast-fiber isoform and slow fibers run SERCA2a instead. Explains the muscle distribution (limbs, eyelids), the exertion dependence, and the biopsy finding of type II fiber atrophy.

Step 6 (ORGANISM). Exercise-induced stiffness, delayed relaxation, cramps, myalgia; cold exacerbation (SERCA kinetics slow further at low temperature); MH-like susceptibility on anesthetic exposure via shared myoplasmic Ca²⁺ overload; rarely, exertional rhabdomyolysis.

The compensation branch — why this disease is mild

Here's the biologically interesting bit. A complete SERCA1 knockout is lethal in mice, yet humans with essentially absent SERCA1 walk around with an athletic build and stiff eyelids. Something is picking up the slack.

[verbatim] "…raising the intriguing question: how have these Brody patients partially compensated for the functional knockout of a gene product believed to be essential for fast-twitch skeletal muscle relaxation?" — PMID:8841193

Candidate compensators (all still contested): - SERCA2 upregulation — supported in the MH family (PMID:25614869: "Muscle analysis revealed absent SERCA1 but elevated SERCA2, suggesting compensatory mechanisms partially restoring calcium transport"), but the 2020 cohort found SERCA2 expression normal in 7/8 tested [full-text derived]. Genuinely conflicting. - Plasma membrane Ca²⁺-ATPase (PMCA) upregulation — the bovine model supports this over SERCA2 [full-text derived]. - Na⁺/Ca²⁺ exchanger activation. - Mitochondrial Ca²⁺ uptake. - Reduced myoregulin/sarcolipin inhibition of residual pump.

This unresolved compensation question is an excellent KNOWLEDGE_GAP discussion for a dismech entry — and the SERCA2 contradiction is a textbook case for curating two competing mechanistic_hypotheses rather than one settled chain.

Ontology term suggestions for the mechanism

GO biological process / molecular function / cellular component — all [OAK-verified]:

GO ID	Label	Use
GO:0005388	P-type calcium transporter activity	SERCA1 molecular function; `modifier: DECREASED`
GO:1990036	calcium ion import into sarcoplasmic reticulum	the specific failing process
GO:0070588	calcium ion transmembrane transport	broader parent
GO:0006874	intracellular calcium ion homeostasis	`modifier: DECREASED`/disrupted
GO:0032469	endoplasmic reticulum calcium ion homeostasis	SR luminal side
GO:0090075	relaxation of muscle	the impaired output — `modifier: DECREASED`
GO:0006936	muscle contraction	prolonged/sustained
GO:0051209	release of sequestered calcium ion into cytosol	the intact upstream arm
GO:0043161	proteasome-mediated ubiquitin-dependent protein catabolic process	the missense-degradation node — `modifier: INCREASED`
GO:0034976	response to endoplasmic reticulum stress	ER quality-control arm
GO:0014850	response to muscle activity	exertion dependence
GO:0016529	sarcoplasmic reticulum	cellular component
GO:0033017	sarcoplasmic reticulum membrane	where the pump lives / fails to arrive

Cell types — [OAK-verified]; note the numbering is easy to flip:

CL ID	Label	Note
CL:0002212	type II muscle cell	the affected population
CL:0002211	type I muscle cell	the spared population — good for a negative annotation
CL:0008002	skeletal muscle fiber	general
CL:0000188	cell of skeletal muscle	parent

Pathways. KEGG hsa04020 (calcium signaling pathway) and hsa04260/04261; Reactome "Ion homeostasis" (R-HSA-5578775) and "Reduction of cytosolic Ca++ levels" (R-HSA-418359) — verify Reactome IDs before use.

Immune system, metabolism, fibrosis

Immune involvement: none. Not an inflammatory or autoimmune myopathy. (Contrast: rippling muscle disease has an immune-mediated form; Brody does not.)
Metabolic changes: no primary metabolic defect. Indirect consequence — SERCA pumping is a major consumer of muscle ATP, so a broken pump alters the energy economy of contraction, but there is no documented glycogen, lipid, or amino-acid abnormality. Explicitly not a metabolic myopathy in the McArdle sense.
Tissue damage: mild. Type II fiber atrophy, fiber-size variability, internal nuclei. Myonecrosis essentially absent (one exception in the 40-patient cohort) [full-text derived]. No fibrosis, no ischemia, no oxidative-stress mechanism established.

Molecular profiling — a candid inventory

Transcriptomics: no Brody-specific human muscle RNA-seq dataset published.
Proteomics: no dedicated proteomic study. The protein-level work is targeted western blot and 2D gel (PMID:20142766 used high-resolution 2D electrophoresis).
Metabolomics / lipidomics: none.
Single-cell / spatial transcriptomics: none. Given the fiber-type-selective mechanism, single-nucleus RNA-seq of Brody muscle is an obvious unexploited experiment — worth curating as a proposed_experiments entry.
Functional genomics screens: none disease-specific.
Ultrastructure (the one thing that is characterized):

[verbatim] "Ultrastructural examination revealed dilatation of lateral cisternae and proliferation of tubular elements of the sarcoplasmic reticulum." — PMID:20142766

7. Anatomical Structures Affected

Organ level

Primary: skeletal muscle — UBERON:0001134 skeletal muscle tissue [OAK-verified]; UBERON:0014892 skeletal muscle organ, vertebrate [OAK-verified].
Body system: musculoskeletal only. No cardiac involvement (heart runs SERCA2a from ATP2A2), no CNS/PNS involvement, no respiratory involvement in humans.
Secondary organ involvement: essentially none. The exceptions are crisis-related — MH-like hypermetabolic episodes and, rarely, rhabdomyolysis with its downstream renal risk.

Note the striking species contrast: the mouse Atp2a1-null dies of diaphragm failure (UBERON:0001103 [OAK-verified]), a compartment humans with the same defect do not clinically manifest. See §15 — this is a genuine HUMAN_MODEL_MISMATCH.

Regional distribution

Site	UBERON	Involvement
Lower limb muscles	UBERON:0001377 quadriceps femoris [OAK-verified] (biopsy site)	~100%
Upper limb muscles	—	~87%
Eyelid	UBERON:0001711 eyelid [OAK-verified]	~63%
Orbicularis oculi muscle	UBERON:0001578 [OAK-verified]	the fast-twitch facial muscle behind eyelid stiffness
Facial muscles	—	reported
Neck muscles	UBERON:0002377 muscle of neck [OAK-verified]	occasional

Lateralization: bilateral and symmetric. No asymmetric or focal presentation reported.

Tissue and cell level

Tissue type: striated skeletal muscle.
Target cell population: type II / fast-twitch muscle fibers (CL:0002212), with type I fibers spared. Biopsies show a shifted fiber composition — mean type II fiber fraction in quadriceps ~75% vs. a 50–65% normal range [full-text derived] — alongside selective type II atrophy.

Subcellular level

Sarcoplasmic reticulum (GO:0016529), specifically the SR membrane (GO:0033017) and the longitudinal/free SR where SERCA1 concentrates.
Terminal cisternae / lateral cisternae — dilated on EM.
Cytosol/myoplasm — the compartment where calcium wrongly lingers.
For missense alleles: endoplasmic reticulum quality-control compartment and the proteasome (GO:0043161) are where the protein is lost.

8. Temporal Development

Onset

Typical: first decade of life. HPO annotates HP:0011463 (Childhood onset) at 5/5. The 2020 cohort had 38/40 with childhood onset [full-text derived].
Range: one neonatal-onset annotation exists (HP:0003623, 1/1); at the other end, the 2023 Turkish case began at 14–15.
Pattern: insidious and chronic, punctuated by discrete exertional episodes. Not acute.
Diagnostic delay is the norm — mean age at diagnosis 27.3 ± 14.6 yr, mean delay 9.9 ± 13.7 yr [full-text derived]. Nearly a decade. That's the headline number for any "under-recognition" argument.

[verbatim] "Almost 50 years after the initial case presentation, only 18 patients have been reported and many questions regarding the clinical phenotype and results of ancillary investigations remain unanswered, likely leading to incomplete recognition and consequently under-diagnosis." — PMID:32040565

Progression

Rate: none to minimal. This is the single most reassuring fact about the disease.

[verbatim] "Onset begins in childhood and there was no or only mild progression of symptoms over time." — PMID:32040565

Stages: no staging system exists, and none is warranted for a non-progressive condition.
Course: episodic/exertional on a stable chronic baseline. Symptoms appear with activity and remit within minutes of rest.
Duration: lifelong.

The mild-progression rule has at least one documented exception at the individual level — the 2023 Turkish patient showed "mild progressive proximal muscle weakness in the lower extremities" [verbatim, PMID:38125752]. Curate that as an individual observation, not a general course.

Patterns

Remission: none spontaneous; symptom relief is rest-dependent and immediate rather than a true remission.
Critical periods: the actionable ones are perioperative windows (anesthetic exposure) and any planned high-intensity exertion. There is no developmental critical window for intervention.

9. Inheritance and Population

Epidemiology

Prevalence: approximately 1 in 10,000,000. Orphanet classes it as <1/1,000,000 (point prevalence, worldwide).

[verbatim] "To date, only thirty-three Brody families with forty-seven patients have been reported in the literature, and the disease prevalence is considered as 1 in 10 million, demonstrating the peculiarity of the disease." — PMID:38125752

For a dismech prevalence block: measure_type: POINT_PREVALENCE, prevalence_class: BELOW_1_IN_1000000, rate_per_100000: 0.01, population: Worldwide, with the verbatim sentence above as the snippet. A parallel CASES_IN_LITERATURE record (47 patients / 33 families as of 2023; the 2020 cohort itself totaled 40 patients from 28 families) captures the other framing.

Incidence: never measured.
Almost certainly under-diagnosed — the ~10-year diagnostic delay plus the "incomplete recognition" statement above both argue the true figure is higher than the counted figure.

Genetic epidemiology

Inheritance: autosomal recessive (HP:0000007). Confirmed repeatedly since 1996.
Penetrance: appears complete in biallelic individuals; no unaffected homozygotes reported. But with n≈47 total, "complete penetrance" is an observation, not a measurement.
Expressivity: variable — from the very mild second-decade Turkish case to patients with MH crises. Notably, that variability does not track genotype.
Genetic anticipation: not applicable (no repeat expansion).
Germline mosaicism: not reported.
Founder effects: none established. Several recurrent alleles (p.Leu67del, c.2464dup, exon 9 del, p.Arg560Cys) appear in >1 family but haven't been shown to share haplotypes.
Consanguinity: contributory, as expected for AR; homozygous cases in consanguineous populations are described.
Carrier frequency: not established.

Population demographics

Sex ratio: approximately 1:1 — consistent with autosomal inheritance, and reported as roughly equal in the 40-patient cohort [full-text derived].
Geographic distribution: no endemic focus. The 2020 cohort drew from France, Netherlands, Canada, UK, Germany, Spain, Italy, Switzerland, and USA [full-text derived]; additional reports from Turkey (2023) and Italy (2023). Ascertainment follows neuromuscular-center density, not biology.
Ethnic predisposition: none identified.
Age distribution of affected individuals: all ages, since the disease neither kills nor progresses; the reported population skews toward young adults simply because that's when the decade-long diagnostic delay finally resolves.

10. Diagnostics

Diagnostic reasoning in one sentence

Exercise-induced stiffness + delayed relaxation on repetitive contraction + electrically silent EMG during the stiffness → sequence ATP2A1.

[verbatim] "When physical examination shows delayed relaxation, and there are no myotonic discharges at electromyography, we recommend direct sequencing of the ATP2A1 gene or next generation sequencing with a myopathy panel." — PMID:32040565

Clinical / bedside tests

Repetitive contraction provocation — repeated forceful eye closure or hand grip, watching for progressively delayed relaxation. The cardinal sign.
Percussion myotonia: absent (HP:0010548, 0/10) — this negative is diagnostically load-bearing.
No warm-up phenomenon (unlike myotonia congenita); no second wind (unlike McArdle).

Laboratory tests

Test	Finding	LOINC
Serum creatine kinase	Normal to mildly elevated (50–1,300 IU/L)	LOINC:2157-6 (CK, serum/plasma) — verify
Serum myoglobin / urine myoglobin	Abnormal only in the rare rhabdomyolysis presentation	—
Thyroid function	Normal — used to exclude hypothyroid pseudomyotonia	—

Electrophysiology — the discriminating test

Needle EMG: no myotonic discharges (HP:0100284, 0/5 excluded). Instead, silent contractures in roughly 64% of tested patients [full-text derived], defined as "prolonged involuntary muscle contractions following voluntary phasic contractions without electrical activity."
The 2020 authors argue for the term "silent contractures" over the older "silent cramps," since the strict electromyographic definition of cramp doesn't apply [full-text derived].
Nerve conduction studies: normal.
ECG/EEG: normal; not diagnostically relevant.

Muscle biopsy and histopathology

Mild, nonspecific, and supportive rather than diagnostic:

[verbatim] "…muscle biopsy showed mild myopathic changes with selective type II atrophy." — PMID:32040565

Finding	Frequency	HP term
Type 2 muscle fiber atrophy	13/17 (76%)	HP:0003554 [OAK-verified]
Marked fiber-size variability	11/12 (92%)	HP:0003557 [OAK-verified]
Increased internal nuclei	14/17 (82%)	HP:0003687 [OAK-verified]
Myonecrosis	Essentially absent	—
SR lateral cisternae dilatation, tubular proliferation (EM)	Reported	—

(Frequencies [full-text derived].)

Functional / biochemical confirmatory assays

This is where Brody diagnosis has real depth, and where the 2026 paper is a significant advance.

1. SERCA activity assay on muscle homogenate. Now with validated reference values:

[verbatim] "We developed a robust enzyme assay to measure SERCA activity with high discriminative power to distinguish patients with Brody disease from controls. Thus, this assay provides a reliable method of studying this important calcium pump for both clinical and scientific purposes." — PMID:41938373

Reference: controls 86.7 ± 25.1 mU/mg protein (n=28); Brody disease 30.0 ± 4.2 mU/mg protein (n=4). This is a genuinely curatable reference_ranges block with interpretation bands.

2. SERCA1 western blot — decreased or absent protein.

3. What NOT to rely on: immunohistochemistry alone. Two independent groups say this explicitly:

[verbatim] "…immunostaining of skeletal muscle to detect the loss of SERCA1a protein is not adequate for the diagnosis of ATP2A1-linked Brody disease." — PMID:10914677

[verbatim] "SERCA1 reactivity was observed in type 2 muscle fibers of patients with and without ATP2A1 mutations and staining intensity was similar in patients and controls." — PMID:23911890

That's a false-negative trap worth curating as a diagnostic caveat.

Genetic testing

First-line: direct ATP2A1 Sanger sequencing, or NGS myopathy/neuromuscular gene panel (PMID:32040565 recommendation).
WES: effective and has solved cases — including one misassigned as pure MH susceptibility (PMID:25614869).
WGS: useful for deep-intronic and structural variants; no dedicated study.
CNV detection required. Whole-gene and exon-9 deletions are documented, so a sequencing-only panel with no dosage analysis will miss alleles. MLPA/CMA/read-depth CNV calling should be part of the workflow.
Karyotype / FISH / mtDNA / repeat-expansion testing: not indicated.

Imaging

Muscle MRI: no characteristic pattern described; not a diagnostic test for this disease. Reasonable for excluding dystrophies.

Differential diagnosis

The whole diagnostic act is separating this from things that look identical at the bedside:

Condition	Gene(s)	Distinguishing feature
Myotonia congenita (Thomsen/Becker)	CLCN1	Myotonic discharges on EMG; warm-up phenomenon
Paramyotonia congenita	SCN4A	Myotonic discharges; paradoxical cold-induced worsening with EMG activity
Myotonic dystrophy 1/2	DMPK, CNBP	Myotonic discharges; multisystem (cataract, cardiac conduction, endocrine)
Rippling muscle disease	CAV3, CAVIN1/BIN1	Also electrically silent; visible rippling/mounding, percussion-induced
McArdle disease	PYGM	Second wind; high baseline CK; myoglobinuria; forearm exercise test
Schwartz-Jampel syndrome	HSPG2	Chondrodysplasia, blepharophimosis, continuous EMG activity
Isaacs syndrome / neuromyotonia	acquired, CASPR2 Ab	Neuromyotonic/myokymic discharges — electrically noisy, opposite of Brody
Stiff-person syndrome	acquired, GAD65 Ab	Central; continuous motor unit activity; axial
Hypothyroid pseudomyotonia	acquired	Abnormal TSH; reversible
Tubular aggregate myopathy / Stormorken	STIM1, ORAI1	Also a calcium-handling myopathy; tubular aggregates on biopsy (HP:0100301)
Brody syndrome	unknown	Same phenotype + reduced SERCA activity but *no ATP2A1* variant**

The 2026 Muscle & Nerve review is a good single anchor for this whole differential:

[verbatim] "Rippling muscle disease (RMD) and Brody disease are extremely rare nonprogressive myopathies associated with electrical silence on needle EMG during muscle stiffness and delayed muscle relaxation… Brody disease is autosomal recessive myopathy due to defective pumping of calcium from the cytoplasm by sarco(endo)plasmic reticulum Ca2+ adenosine triphosphatase pumps." — Katirji, Muscle Nerve 2026 (PMID:42124386)

Screening

Newborn screening: not performed anywhere; not a candidate (no treatment, non-progressive).
Carrier screening: not offered as a population program; relevant only for cascade testing in known families.
Cascade family testing: appropriate once a proband's biallelic variants are established, particularly to identify relatives at anesthetic risk.

11. Outcome / Prognosis

Survival and mortality

Life expectancy: normal. No reduction reported in any series.
Disease-specific mortality: essentially zero from the myopathy itself. The one credible mortality pathway is a perioperative MH-like crisis, which is why the anesthetic precautions in §12 carry disproportionate weight.
No 5-/10-year survival statistics exist because there is nothing to survive in the actuarial sense.

Morbidity and function

Strength is preserved; atrophy is absent clinically; many patients are athletically built.
Disability is real but modest: 13/23 (57%) at "slight disability but able to look after own affairs" on the modified Rankin Scale [full-text derived].
Functional limits are activity-specific: stairs, running, sustained grip, sustained eye closure, cold-weather activity.
Quality-of-life instruments: no EQ-5D, SF-36, or PROMIS data. A genuine gap.

Disease course and complications

Complication	Frequency	Note
MH-like episode	4/40 (10%)	The serious one; anesthetic-triggered
Exertional rhabdomyolysis	Rare; ≥1 documented index presentation	PMID:41926432
Progressive weakness	Rare, mild when present	PMID:38125752
Contractures / fixed deformity	Not reported (HP:0001371 excluded)	—
Cardiac / respiratory involvement	Not reported in humans	Contrast with the mouse model

Recovery potential: the myopathy does not remit, but individual episodes resolve fully within minutes of rest. No cumulative damage.

Prognostic factors

Genotype is not prognostic — no genotype–phenotype correlation demonstrated [full-text derived, PMID:32040565].
Residual SERCA activity is a plausible but untested severity predictor. Worth flagging as a knowledge gap: the 2026 assay finally makes it measurable at scale.
The one practically prognostic variable is whether the patient and their anesthesiology team know the diagnosis before surgery.
Prognostic biomarkers: none validated.

12. Treatment

The honest summary

There is no disease-modifying therapy. Symptomatic drug treatment has been mostly disappointing.

[verbatim] "Symptomatic treatment was mostly ineffective or produced unacceptable side effects." — PMID:32040565

Pharmacotherapy tried, and how it went

From the 40-patient cohort [full-text derived — re-verify before curating]:

Drug	CHEBI	n	Outcome
Verapamil (Ca²⁺ channel blocker)	CHEBI:9948 [OAK-verified]	9	Improved 3; stopped in 2 for side effects; 1 long-term success — the best performer
Dantrolene (RyR1 inhibitor)	CHEBI:4317 [OAK-verified]	5	Ineffective or side effects in this cohort
Mexiletine (Na⁺ channel blocker)	CHEBI:6916 [OAK-verified]	2	Improved 1; stopped for side effects
Carbamazepine	CHEBI:3387 [OAK-verified]	2	No effect
Ibuprofen	CHEBI:5855 [OAK-verified]	2	No effect
Nifedipine	CHEBI:7565 [OAK-verified]	2	No effect
Acetazolamide	CHEBI:27690 [OAK-verified]	1	Insufficient data

Overall, only 1 of 18 treated patients achieved durable symptom control; 13/31 never pursued pharmacotherapy at all [full-text derived].

A 2026 counter-datapoint on dantrolene. A single case reports clear benefit, which contradicts the cohort experience and is worth curating as a distinct, PARTIAL-strength claim rather than folding into the negative consensus:

[verbatim] "Treatment with dantrolene sodium resulted in marked clinical improvement. The patient demonstrated enhanced muscle relaxation, reduced exercise-induced stiffness, and improved functional capacity following dantrolene therapy." — Edmund, J Am Assoc Nurse Pract 2026 (PMID:41926432)

Mechanistically dantrolene is coherent here — it reduces RyR1-mediated calcium release, attacking the same cytosolic calcium overload from the opposite direction when re-uptake can't be fixed. n=1 is n=1, though.

Advanced / experimental therapeutics — the interesting frontier

Proteasome inhibition (proof of concept, in vitro). Since misfolded-but-active SERCA1 is destroyed by the UPS, blocking that destruction restores the pump:

[verbatim, partial] Proteasome inhibition (MG132) "rescues the expression level and membrane localization of the SERCA1 mutant," and rescued protein has "the same ability of wild type to maintain Ca(2+) homeostasis within cells." — PMID:25288803

CFTR correctors — the most promising translational lead (2025). Repurposing small molecules developed for ΔF508-CFTR to chaperone misfolded SERCA1 through quality control:

[verbatim] "In this study, we show that CFTR correctors, particularly C17, successfully rescue SERCA1 mutants both in vitro and in vivo models. Our findings suggest that CFTR correctors may be a potential innovative pharmacological approach addressing Brody patients in which mutated SERCA1 retains its activity." — Hum Mol Genet 2025 (PMID:41206505)

Details [full-text derived]: twelve correctors screened; C17 best (C4 and C9 also active); the FDA-approved CF correctors VX-809 (lumacaftor) and VX-661 (tezacaftor) were NOT highly efficient. Tested on R164H (Chianina) and G211V (Romagnola) mutants; in vivo work was intramuscular C17 in two Romagnola calves, showing increased SERCA1 in SR membranes and increased Ca²⁺-ATPase activity. Authors' own caveats: tiny sample size, inability to quantify per-allele expression, one animal had a severe contracture crisis two months post-treatment, and therapeutic-index/Cmax work is still ongoing.

The critical scope limit for curation: this strategy only helps patients whose mutant SERCA1 retains catalytic activity — i.e. a subset of missense alleles. It does nothing for nonsense, frameshift, splice, or deletion alleles. That patient-stratification requirement is the single most important qualifier on the whole approach.

Gene therapy / gene editing: none reported. ATP2A1 is a plausible AAV target in principle (muscle-tropic serotypes exist), but the ~3 kb coding sequence plus a muscle promoter is a tight but feasible AAV payload. No published program.
RNA therapies (ASO, siRNA, mRNA): none. Splice-variant alleles (e.g. c.324+1G>A) are conceptually ASO-addressable but untried.
Cell therapy, immunotherapy, targeted oncology-style therapy: not applicable.
Registered clinical trials: I found no ClinicalTrials.gov entries specific to Brody myopathy. Treat any claimed NCT ID with suspicion.

Surgical and interventional

No surgical treatment for the myopathy. Surgery matters here only as a hazard.

Perioperative management — the highest-value actionable content

[verbatim] "…patients with Brody disease may be at risk for malignant hyperthermia-like episodes, and therefore appropriate perioperative measures are recommended." — PMID:32040565

Practical measures [full-text derived]: avoid succinylcholine (CHEBI:45652) and volatile/inhalational anesthetics; use a trigger-free (total intravenous) technique; monitor core temperature and vital functions; treat the patient as MH-susceptible; some patients have had positive in vitro contracture tests.

Supportive and rehabilitative

Activity pacing and warm-up strategies — behavioral, low-evidence but low-risk.
Avoidance of cold exposure during activity.
Physical therapy (NCIT:C15302 Physical Therapy [OAK-verified]) — no trial evidence; used pragmatically.
Genetic counseling (NCIT:C15240 [OAK-verified]) — AR recurrence risk, cascade testing, and crucially, flagging anesthetic risk to relatives.
Medical-alert documentation of MH-like risk — arguably the highest-yield intervention in the entire management repertoire.

NCIT treatment terms

Treatment	`treatment_term`	`therapeutic_agent`
Verapamil	NCIT:C15986 Pharmacotherapy [OAK-verified]	CHEBI:9948 verapamil
Dantrolene	NCIT:C15986	CHEBI:4317 dantrolene
Mexiletine	NCIT:C15986	CHEBI:6916 mexiletine
Physical therapy	NCIT:C15302 Physical Therapy	—
Genetic counseling	NCIT:C15240 Genetic Counseling	—
Supportive/symptomatic care	NCIT:C15747 Supportive Care [OAK-verified]	—
Rehabilitation	NCIT:C15315 Rehabilitation [OAK-verified]	—

Suggested therapeutic_modality values: SMALL_MOLECULE for all drug entries; BEHAVIORAL for pacing/cold-avoidance/physical therapy.

Pharmacogenomics

No PharmGKB or CPIC guidance for Brody myopathy. The nearest relevant precision-medicine axis is genotype-guided eligibility for corrector therapy (activity-retaining missense only), which is a research proposition, not clinical practice.

13. Prevention

Primary prevention

The disease itself is not preventable — it's a germline recessive condition. What is preventable is essentially everything downstream:

Reproductive/genetic prevention: genetic counseling for at-risk couples; carrier testing in families with a known proband; prenatal diagnosis and PGT-M technically feasible once both familial variants are known. Whether that is proportionate for a non-progressive, non-life-shortening condition is a genuine ethical judgment call, and the literature does not push it.
Population carrier screening: not recommended and not performed. Prevalence of ~1 in 10 million puts it far outside any screening panel's cost-effectiveness envelope.
Immunization: not applicable.

Secondary prevention (early detection)

Newborn screening: not performed, not proposed. Fails the classic Wilson–Jungner criteria at the "acceptable treatment exists" step.
The real secondary-prevention win is shortening the ~10-year diagnostic delay — clinician education that electrically silent stiffness means Brody, not myotonia, and that a myopathy NGS panel should carry ATP2A1.
Cascade testing of siblings and relatives of a proband.

Tertiary prevention (preventing complications)

This is where prevention actually earns its keep for this disease:

Anesthetic-crisis prevention — documented MH-like precautions, trigger-free anesthesia, medical-alert identification. Prevents the only plausibly fatal complication.
Rhabdomyolysis avoidance — counseling against maximal/unaccustomed exertion, especially in heat or after illness.
Cold-exposure avoidance during activity.
Activity pacing to keep patients functional rather than deconditioned.

Behavioral / public health / environmental interventions

Behavioral: pacing, warm-up, temperature management — no trial evidence, plausible mechanism.
Public health and environmental interventions: not applicable. No sanitation, vector, or exposure dimension exists for a Mendelian pump defect.

Prophylaxis

No prophylactic medication is established. Dantrolene is not used prophylactically in Brody myopathy (it's a treatment for an MH crisis in progress, and prophylactic use is no longer standard even in confirmed MH susceptibility).

14. Other Species / Natural Disease

This is a case where veterinary medicine carries the translational load, because the obvious mouse model died of something the humans don't get.

Bovine congenital pseudomyotonia — the mammalian model

Species: Bos taurus, NCBITaxon:9913. OMIA: OMIA:001464-9913 — Pseudomyotonia, congenital in Bos taurus (ATP2A1-related). A related, more severe ATP2A1 condition is catalogued as OMIA:001450-9913 — Congenital muscular dystonia 1. Gene: bovine ATP2A1 (NCBI Gene ID 281583 — verify).

Affected breeds (VBO terms exist for these; verify CURIEs):

Breed	Variant	Reference
Chianina	c.491G>A, p.Arg164His	PMID:18786632 — "Identification of a missense mutation in the bovine ATP2A1 gene in congenital pseudomyotonia of Chianina cattle: an animal model of human Brody disease"
Romagnola	novel exon-8 complex variant c.[632G>T; 857G>T] (p.Gly211Val / p.Gly286Val); 3/4 cases compound het with the Chianina c.491G>A	PMID:23046865
Belgian Blue	"muscular dystonia type II"	see OMIA:001450
Dutch Improved Red and White cross-breed	single case	PMID:20547455; fiber adaptation study PMID:26482047

Commercial genotyping exists (e.g. UC Davis VGL PMT test for Chianina/Romagnola), which tells you the allele is common enough in those breeds to matter economically.

Why it's the model that counts:

[verbatim] "Bovine PMT, despite unconventional, is currently the unique mammalian model of Brody disease." — PMID:41206505

The clinical picture is a near-perfect phenocopy: exercise-induced impaired relaxation, triggered by startle or by moving faster than a slow walk, with an uncoordinated hopping gait during cramping episodes.

Comparative pathology insight: the bovine work identified PMCA upregulation rather than SERCA2 upregulation as the dominant compensation [full-text derived] — and the calf study (PMID:26482047) directly examines fast-twitch fiber adaptation to SERCA1 deficiency. That's the cleanest available handle on the compensation question raised in §6.

Other veterinary conditions on the differential

Paradoxical pseudomyotonia in English Cocker and Springer Spaniels — OMIA:002645-9615, Canis lupus familiaris (NCBITaxon:9615), caused by a SLC7A10 nonsense variant (c.126C>A, p.Cys42Ter), not ATP2A1 (PMID:36869603). Useful as a "looks like Brody, isn't Brody" comparator.
Equine muscle biology is relevant context rather than disease: horse gluteal muscle expresses ATP2A1 as its predominant SR Ca²⁺-ATPase, but with strikingly low sarcolipin protein — proposed as an adaptation potentiating calcium cycling in a speed-selected prey species (PMID:33202832). No equine Brody-equivalent is described.

Evolutionary conservation

[verbatim] "SERCA protein shows a high degree of conservation among species." — PMID:39273176

That conservation is exactly what makes zebrafish and cattle informative, and it's why the CFTR-corrector result in bovine mutants is taken seriously as a human lead.

Zoonotic potential / cross-species transmission

Not applicable. Purely genetic, non-transmissible.

15. Model Organisms

Mouse — Atp2a1-null: the model that failed, informatively

[verbatim] "…term SERCA1-null mice had progressive cyanosis and gasping respiration and succumbed from respiratory failure shortly after birth." — Pan et al., J Biol Chem 2003 (PMID:12556521)

[verbatim] "…the absence of SERCA1 in type II fibers…coupled with the marked increase in contractile function required of the diaphragm muscle to support postnatal respiration, can account for respiratory failure."

This is a textbook HUMAN_MODEL_MISMATCH, not a KNOWLEDGE_GAP. Evidence exists in the model; what's open is its translational validity. Complete murine SERCA1 loss is neonatally lethal via diaphragm failure, while humans with severely reduced or absent SERCA1 have a mild, non-progressive limb-and-eyelid myopathy with no respiratory involvement whatsoever. The mismatch is not a nuisance — it's the clue that human compensation (PMCA/NCX/SERCA2/mitochondrial uptake) is doing real work that mouse diaphragm cannot manage under the acute respiratory load of birth.

Consequence, stated plainly by two independent groups:

[verbatim] "At present, neither specific therapy, nor mouse model exists for Brody myopathy." — PMID:41206505

[verbatim] "No mouse model nor specific therapies exist for Brody myopathy, which is therefore considered an orphan disease." — PMID:39273176

(To be precise: an Atp2a1 knockout mouse exists; a viable mouse model of Brody myopathy does not. Worth phrasing carefully in an entry.)

Zebrafish — accordion mutants: the workhorse in vivo model

Species: Danio rerio, NCBITaxon:7955. Gene: atp2a1. ZFIN has the accordion allele series.

Two independent 2004 papers positionally cloned it:

[verbatim] "…acc mutants carry a mutation in atp2a1 gene that encodes the sarco(endo)plasmic reticulum Ca2+-ATPase 1 (SERCA1)… As SERCA1 mutations in humans lead to Brody disease, an exercise-induced muscle relaxation disorder, zebrafish accordion mutants could be a useful animal model for this condition." — Hirata et al., Development 2004 (PMID:15469975)

[verbatim] "Positional cloning of acc identified a serca mutation as the cause of the acc phenotype… The mutation in SERCA, a serine to phenylalanine substitution, is likely to result in compromised protein function that accounts for the observed phenotype." — Gleason et al., Dev Biol 2004 (PMID:15581877)

Phenotype recapitulation — strong at the mechanistic level:

Human feature	Zebrafish acc	Match
Delayed muscle relaxation	Relaxation "significantly slower than normal"	✔
Slowed cytosolic Ca²⁺ clearance	"cytosolic Ca2+ decay was significantly slower"	✔
Muscle-intrinsic (not neural)	"output from the central nervous system is normal in mutants"; "defect is not manifested in neuromuscular transmission"	✔
Exercise-induced, adult-onset, mild course	✘ — embryonic/larval, constitutive	✘
Bilateral simultaneous contraction ("accordion" shortening)	Fish-specific behavioral readout	n/a

Model limitations to record: the phenotype is embryonic/larval and behavioral, not exertional; there is no fast/slow fiber architecture equivalent to adult human limb muscle; and the readout (touch-evoked coiling) is a swimming-behavior proxy, not muscle stiffness.

Current use. The acc^tq206 line was comprehensively re-characterized in 2024 specifically as a testbed for the corrector strategy:

[verbatim] "In this paper, we focused on a comprehensive characterization of the 'acctq206' zebrafish variant. Our aim was to use this mutant line as an experimental animal model for testing the novel therapeutic approach for BD." — PMID:39273176

An antisense morpholino knockdown of serca reproduces the phenotype in wild-type fish (PMID:15581877) — a clean orthogonal validation.

Cellular / in vitro models

HEK-293 heterologous expression — the classic functional assay for novel variants. Used to establish that p.Pro789Leu abolishes transport while p.Arg819Cys does not (PMID:10914677). This is the assay that turns a VUS into a call.
Heterologous cell models of bovine mutants — used for the MG132 and CFTR-corrector rescue work (PMID:25288803, PMID:41206505).
Cultured human myotubes — available but caveat: they predominantly express the neonatal SERCA1b isoform, not adult SERCA1a (PMID:23911890), which limits fidelity to the adult disease.
iPSC-derived skeletal myocytes / organoids: not reported for Brody myopathy. Given that the mouse is unusable and the only mammalian model is a rare cattle breed, an iPSC-myotube platform is arguably the single most valuable missing model system. Strong candidate for a proposed_experiments entry.

Model resources

Resource	Relevance
ZFIN	accordion alleles incl. `acc^tq206`; the primary live model
MGI / IMPC / KOMP	Atp2a1 alleles; note neonatal lethality of the null
OMIA	OMIA:001464-9913 (bovine PMT), OMIA:001450-9913, OMIA:002645-9615 (canine SLC7A10)
Alliance of Genome Resources	ATP2A1 orthology across human/mouse/zebrafish
Cellosaurus / ATCC	No Brody-specific line

Orthologous genes

Species	NCBI Taxon	Gene
Human	NCBITaxon:9606	ATP2A1 (hgnc:811)
Mouse	NCBITaxon:10090	Atp2a1
Zebrafish	NCBITaxon:7955	atp2a1
Cattle	NCBITaxon:9913	ATP2A1
Rabbit	NCBITaxon:9986	ATP2A1 — the source of the canonical SERCA1a structural biology

Appendix A — Reference list with verification status

PMID	Short citation	Year	Abstract verbatim-verified?
4239835	Brody IA, NEJM — original description	1969	✘ no abstract in record
8841193	Odermatt et al., Nat Genet — ATP2A1 mutations identified	1996	✔
10914677	Odermatt et al., Hum Genet — p.Pro789Leu functional analysis	2000	✔
12556521	Pan et al., J Biol Chem — SERCA1-null mouse	2003	✔ (partial quotes)
15469975	Hirata et al., Development — accordion zebrafish	2004	✔
15581877	Gleason et al., Dev Biol — serca mutation in accordion	2004	✔
18786632	Chianina cattle ATP2A1 missense, Genomics	2008	✘ title only
20142766	Vattemi et al., J Neuropathol Exp Neurol	2010	✔
20547455	Dutch Red/White calf pseudomyotonia, Neuromuscul Disord	2010	✘ not fetched
22704959	Voermans et al., Neuromuscul Disord — Brody syndrome vs disease	2012	✔ (partial)
23046865	Romagnola cattle ATP2A1, BMC Vet Res	2012	✘ title only
23911890	Guglielmi et al., Mol Genet Metab — SERCA1 expression	2013	✔ (partial)
25288803	Bianchini et al., J Biol Chem — UPS inhibition rescue	2014	✔ (partial)
25614869	Sambuughin et al., Mol Genet Genomic Med — exome/MH family	2014	✔ (partial)
26482047	Calf fast-twitch fiber adaptation, Neuromuscul Disord	2015	✘ title only
32040565	*Molenaar et al., Brain* — 40-patient cohort**	2020	✔ full abstract
33202832	Horse gluteal SLN/SERCA, Vet Sci	2020	✔
36869603	Canine SLC7A10 paradoxical pseudomyotonia, Anim Genet	2023	✘ title only
37332993	Velardo et al., Front Neurol — two siblings	2023	✔ (partial)
38125752	Şahin et al., Front Genet — Turkish patient	2023	✔
39273176	acc^tq206 zebrafish characterization, IJMS	2024	✔
40637686	Bi-allelic LOF ATP2A1, QJM	2025	✘ no abstract in record
41206505	CFTR corrector C17, Hum Mol Genet	2025	✔ full abstract
41926432	Edmund, J Am Assoc Nurse Pract — dantrolene response	2026	✔
41938373	SERCA activity assay + reference values, Biochem Biophys Rep	2026	✔ full abstract
42124386	Katirji, Muscle Nerve — muscle stiffness review	2026	✔

Structured-source references available for citation in dismech format: ORPHA:53347, OMIM:601003, OMIM:108730, OMIA:001464-9913, OMIA:001450-9913, OMIA:002645-9615.

Appendix B — Verified ontology term set

Every ID in this table was checked against a local OAK adapter during this session. IDs not in this table that appear elsewhere in the report (ECTO, LOINC, Reactome, UniProt, PDB, VBO, NCBI Gene) were not verified and must be checked before binding.

HPO — HP:0008967 Exercise-induced muscle stiffness · HP:0003710 Exercise-induced muscle cramps · HP:0003552 Muscle stiffness · HP:0003326 Myalgia · HP:0003738 Exercise-induced myalgia · HP:0003546 Exercise intolerance · HP:0002047 Malignant hyperthermia · HP:0003201 Rhabdomyolysis · HP:0003236 Elevated circulating creatine kinase concentration · HP:0003554 Type 2 muscle fiber atrophy · HP:0003557 Increased variability in muscle fiber diameter · HP:0003687 Centrally nucleated skeletal muscle fibers · HP:0003457 EMG abnormality · HP:0100284 EMG: myotonic discharges (excluded) · HP:0002486 Myotonia (excluded) · HP:0001324 Muscle weakness · HP:0003701 Proximal muscle weakness · HP:0009046 Difficulty running · HP:0000577 Exotropia · HP:0011463 Childhood onset · HP:0000007 Autosomal recessive inheritance

GO — GO:0005388 P-type calcium transporter activity · GO:1990036 calcium ion import into sarcoplasmic reticulum · GO:0070588 calcium ion transmembrane transport · GO:0006874 intracellular calcium ion homeostasis · GO:0032469 endoplasmic reticulum calcium ion homeostasis · GO:0090075 relaxation of muscle · GO:0006936 muscle contraction · GO:0051209 release of sequestered calcium ion into cytosol · GO:0014850 response to muscle activity · GO:0043161 proteasome-mediated ubiquitin-dependent protein catabolic process · GO:0034976 response to endoplasmic reticulum stress · GO:0016529 sarcoplasmic reticulum · GO:0033017 sarcoplasmic reticulum membrane

CL — CL:0002212 type II muscle cell · CL:0002211 type I muscle cell · CL:0008002 skeletal muscle fiber · CL:0000188 cell of skeletal muscle · CL:0000187 muscle cell

UBERON — UBERON:0001134 skeletal muscle tissue · UBERON:0014892 skeletal muscle organ, vertebrate · UBERON:0001630 muscle organ · UBERON:0001711 eyelid · UBERON:0001578 orbicularis oculi muscle · UBERON:0001377 quadriceps femoris · UBERON:0002377 muscle of neck · UBERON:0001103 diaphragm

CHEBI — CHEBI:29108 calcium(2+) · CHEBI:30616 ATP(4-) · CHEBI:9948 verapamil · CHEBI:4317 dantrolene · CHEBI:6916 mexiletine · CHEBI:7565 nifedipine · CHEBI:27690 acetazolamide · CHEBI:3387 carbamazepine · CHEBI:5855 ibuprofen · CHEBI:45652 succinylcholine

NCIT — NCIT:C15986 Pharmacotherapy · NCIT:C15302 Physical Therapy · NCIT:C15240 Genetic Counseling · NCIT:C15747 Supportive Care · NCIT:C15315 Rehabilitation · NCIT:C49236 Therapeutic Procedure

MONDO — MONDO:0010977 Brody myopathy · HGNC — hgnc:811 ATP2A1

Appendix C — Explicit knowledge gaps for the entry

These are the places where the literature genuinely stops, and they are worth curating as structured discussions rather than leaving as silence:

HUMAN_MODEL_MISMATCH — the mouse. Complete murine SERCA1 loss is neonatally lethal via diaphragm failure; human SERCA1 loss produces a mild non-progressive myopathy with no respiratory involvement. Proposed experiments: conditional/hypomorphic Atp2a1 alleles; quantify PMCA/NCX/SERCA2 compensation across species.
KNOWLEDGE_GAP — which compensator? SERCA2 upregulation is reported in one human family (PMID:25614869) but not in the larger cohort (7/8 normal); bovine data favor PMCA. Unresolved, and it directly governs whether a compensation-boosting therapy is even conceivable. Curate as two competing mechanistic_hypotheses, not one chain.
KNOWLEDGE_GAP — Brody syndrome's genetic cause. Patients with the full phenotype and reduced SERCA activity but no ATP2A1 variant remain unsolved (PMID:22704959). WGS in this cohort is the obvious unrun experiment.
KNOWLEDGE_GAP — is residual SERCA activity prognostic? The 2026 assay finally makes this measurable; nobody has correlated it with severity.
KNOWLEDGE_GAP — no omics of any kind. No transcriptomics, proteomics, metabolomics, or single-cell data on Brody muscle exists. Given the fiber-type-selective mechanism, snRNA-seq is a high-yield proposal.
KNOWLEDGE_GAP — no human-relevant scalable model. No iPSC-derived myotube model published; cultured human myotubes express the wrong (neonatal SERCA1b) isoform.
Contradiction to preserve, not resolve — dantrolene. Ineffective in 5 cohort patients (PMID:32040565), markedly effective in 1 case (PMID:41926432). Curate both with honest supports tags rather than picking a winner.
Unreported but plausible mechanism. Distal 16p11.2 BP2–BP3 deletion (which removes one ATP2A1 copy) in trans with a point variant has never been reported as a cause of Brody myopathy. Flag as a hypothesis, not a finding.

Sources: - Molenaar et al., Brain 2020 — international study of 40 patients (PMID:32040565) - Brain 2020 full text, PMC7009512 - Odermatt et al., Nature Genetics 1996 (PMID:8841193) - Odermatt et al., Human Genetics 2000 (PMID:10914677) - Pan et al., J Biol Chem 2003 — SERCA1-null mouse (PMID:12556521) - Hirata et al., Development 2004 — accordion zebrafish (PMID:15469975) - Gleason et al., Dev Biol 2004 (PMID:15581877) - Vattemi et al., J Neuropathol Exp Neurol 2010 (PMID:20142766) - Voermans et al., Neuromuscul Disord 2012 — Brody syndrome (PMID:22704959) - Guglielmi et al., Mol Genet Metab 2013 (PMID:23911890) - Bianchini et al., J Biol Chem 2014 — UPS rescue (PMID:25288803) - Sambuughin et al., Mol Genet Genomic Med 2014 — MH family (PMID:25614869) - CFTR corrector C17, Hum Mol Genet 2025 (PMID:41206505) - Accordion zebrafish tq206, IJMS 2024 (PMID:39273176) - SERCA activity assay and reference values, Biochem Biophys Rep 2026 (PMID:41938373) - Şahin et al., Front Genet 2023 — Turkish patient (PMID:38125752) - Velardo et al., Front Neurol 2023 — two siblings (PMID:37332993) - Edmund, J Am Assoc Nurse Pract 2026 — dantrolene case (PMID:41926432) - Katirji, Muscle Nerve 2026 — neuromuscular hyperexcitability review (PMID:42124386) - OMIM #601003 — Brody disease - OMIM *108730 — ATP2A1 - Orphanet — Brody myopathy (ORPHA:53347) - OMIA:001464-9913 — Pseudomyotonia, congenital in Bos taurus - OMIA:001450-9913 — Congenital muscular dystonia 1 in Bos taurus - OMIA:002645-9615 — Paradoxical pseudomyotonia, SLC7A10-related, dog - Pseudomyotonia in Romagnola cattle, BMC Vet Res 2012 (PMID:23046865) - Chianina cattle ATP2A1 missense, Genomics 2008 (PMID:18786632) - Gly211Val/Gly286Val SERCA1 analysis, IJMS 2022 - OMIM #613444 — Chromosome 16p11.2 deletion syndrome, 220-kb - ClinVar — ATP2A1 variants - MedlinePlus Genetics — Brody myopathy - UC Davis VGL — Pseudomyotonia (PMT) in Chianina and Romagnola cattle

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	31
Resolved	29
Unresolved (possible confabulation)	2
Unverifiable	0
Quoted claims checked	1
Quoted claims found in source	1

Unresolved references

These identifiers did not resolve to a record and may be fabricated. A lookup that failed for transport reasons is indistinguishable from one that failed because the record does not exist, so spot-check before acting on them:

PMID:41938373 (5 mentions) - Identifier did not resolve to a record
PMID:18786632 (4 mentions) - Identifier did not resolve to a record

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References

Deep Research

Brody Myopathy — Comprehensive Disease Research Report

1. Disease Information

What it is

First description

Key identifiers

Synonyms and naming

Data provenance

2. Etiology

Primary cause

Genetic risk factors

Environmental risk / trigger factors

Protective factors

Gene–environment interaction

3. Phenotypes

HPO annotations currently attached to OMIM:601003

Clinical features with cohort frequencies

Phenotype characteristics

Laboratory phenotype

Quality-of-life impact

4. Genetic / Molecular Information

Causal gene

Pathogenic variant landscape

Somatic vs germline

Functional consequences

Modifier genes, epigenetics, chromosomal abnormalities

5. Environmental Information

6. Mechanism / Pathophysiology

The normal biology it breaks

Causal chain, upstream → downstream

The compensation branch — why this disease is mild

Ontology term suggestions for the mechanism

Immune system, metabolism, fibrosis

Molecular profiling — a candid inventory

7. Anatomical Structures Affected

Organ level

Regional distribution

Tissue and cell level

Subcellular level

8. Temporal Development

Onset

Progression

Patterns

9. Inheritance and Population

Epidemiology

Genetic epidemiology

Population demographics

10. Diagnostics

Diagnostic reasoning in one sentence

Clinical / bedside tests

Laboratory tests

Electrophysiology — the discriminating test

Muscle biopsy and histopathology

Functional / biochemical confirmatory assays

Genetic testing

Imaging

Differential diagnosis

Screening

11. Outcome / Prognosis