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Inheritance

1

Autosomal recessive HP:0000007

All four sarcoglycanopathy subtypes are inherited in an autosomal recessive manner; affected individuals carry biallelic pathogenic variants in a single sarcoglycan gene (compound heterozygosity across different sarcoglycan genes does not cause disease).

Autosomal recessive inheritance

Show evidence (1 reference)

PMID:34404573 SUPPORT Human Clinical

"Sarcoglycanopathies are the most severe forms of autosomal recessive limb-girdle muscular dystrophies (LGMDs), constituting about 10-25% of LGMDs."

Establishes autosomal recessive inheritance and the overall severity and relative frequency of the sarcoglycanopathies among LGMDs.

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Subtypes

4

LGMD R3 / alpha-sarcoglycanopathy (LGMD2D; SGCA) MONDO:0011968

SGCA hgnc:10805

Caused by biallelic SGCA (alpha-sarcoglycan, 17q21.33) variants. Presents in childhood with progressive weakness of the pelvic and/or scapular girdle muscles and calf hypertrophy, with wide inter- and intra-familial clinical variability. Alpha-sarcoglycan is added to the sarcoglycan subcomplex last during assembly, docking onto the beta/gamma/delta core. In a large multicenter cohort, mean age at onset was 8 years (later than gamma-sarcoglycanopathy) and 66.7% of patients were wheelchair-bound at mean 22.9-year follow-up.

Show evidence (2 references)

PMID:39174842 SUPPORT Human Clinical

"Limb-girdle muscular dystrophy by alpha-sarcoglycan deficiency or LGMD R3 alpha-sarcoglycan-related is a subtype of the autosomal recessive sarcoglycanopathies caused by variants in the alpha-sarcoglycan gene (SGCA) at 17q21.33. It appears in childhood by progressive weakness of pelvic and/or..."

Confirms SGCA as the causal gene and documents the characteristic childhood-onset presentation of alpha-sarcoglycanopathy.

PMID:33051934 SUPPORT Human Clinical

"The γ-SG patients had earlier disease onset than α-SG patients (5.5 vs. 8 years; p = 0.022) and β-SG patients (24.4 years)."

A 100-patient multicenter cohort quantifies alpha-sarcoglycanopathy onset age relative to the other subtypes.

LGMD R4 / beta-sarcoglycanopathy (LGMD2E; SGCB) MONDO:0011423

SGCB hgnc:10806

Caused by biallelic SGCB (beta-sarcoglycan) variants. Beta-sarcoglycan co-folds with delta- and gamma-sarcoglycan to form the extracellular core of the subcomplex, so its loss is particularly disruptive to complex assembly. Clinically heterogeneous (often, but not always, severe childhood-onset disease; mean onset around 24 years in one multicenter series). Cardiac involvement is common, reported in 63% of a 32-patient cohort, often preceding overt skeletal muscle weakness; 19% required assisted ventilation for restrictive respiratory insufficiency. First-in-human systemic AAV gene replacement therapy has reached Phase 3 (see Treatments).

Show evidence (2 references)

PMID:25862795 SUPPORT Human Clinical

"Cardiac involvement was observed in 20 patients (63%) even before overt muscle involvement. Six patients had restrictive respiratory insufficiency requiring assisted ventilation (19%)."

Quantifies cardiac and respiratory involvement in a 32-patient beta-sarcoglycanopathy (LGMDR4) cohort.

PMID:12868499 SUPPORT Human Clinical

"Given the age profile of the patients studied, the 50% cardiac involvement found in our LGMD2E patients is likely to be a conservative estimate. Careful cardiac monitoring should be carried out in beta-sarcoglycanopathy patients who are at high risk of developing cardiomyopathy."

An earlier, smaller cohort independently documents high cardiac involvement in beta-sarcoglycanopathy/LGMDR4 and establishes the need for cardiac surveillance.

LGMD R5 / gamma-sarcoglycanopathy (LGMD2C; SGCG) MONDO:0009677

SGCG hgnc:10809

Caused by biallelic SGCG (gamma-sarcoglycan, 13q12.12) variants. The first sarcoglycanopathy to be molecularly characterized, and typically the earliest-onset and most severe subtype (mean onset 5.5 years in a 100-patient cohort, versus 8 years for alpha- and 24.4 years for beta-sarcoglycanopathy). Shows strong founder effects in specific populations (>90% of patients homozygous for c.525delT in a French multicenter series; a near-exclusive c.521del founder mutation in Tunisia, historically called "Severe Childhood Autosomal Recessive Muscular Dystrophy"/Tunisian Muscular Dystrophy; a separate C283Y founder mutation in Roma/Gypsy populations across Europe). Frequently Duchenne-like in severity, with high rates of scoliosis, respiratory deficiency, and cardiomyopathy.

Show evidence (3 references)

PMID:40757565 SUPPORT Human Clinical

"The most common symptoms are proximal limb-girdle muscle weakness or wasting (common in about 80-90% of cases); other frequent features are scoliosis (40%) cardiomyopathy (30%), respiratory deficiency (50-60%) and retractions (70%), which are frequently observed especially in advanced cases."

Quantifies the frequency of the major clinical features of gamma-sarcoglycanopathy/LGMDR5 in a contemporary case series and literature review.

PMID:15479193 SUPPORT Human Clinical

"Limb-girdle muscular dystrophy type 2C (LGMD2C) is caused by mutations in the gamma-sarcoglycan gene where a founder Gypsy mutation C283Y was detected. The Bulgarian Gypsy LGMD2C patients, as the Gypsy patients from other countries, were found to be homozygous for this mutation."

Documents the C283Y founder mutation and its high carrier frequency in Roma/Gypsy populations, a distinctive epidemiological feature of gamma-sarcoglycanopathy.

PMID:33051934 SUPPORT Human Clinical

"The α-SG patients showed genetic heterogeneity, whereas >90% of γ-SG patients carried the homozygous c.525delT frameshift variant."

Documents a second, independent gamma-sarcoglycan founder mutation (c.525delT) in a French multicenter cohort, distinct from the C283Y and c.521del founder alleles above.

LGMD R6 / delta-sarcoglycanopathy (LGMD2F; SGCD) MONDO:0011028

SGCD hgnc:10807

Caused by biallelic loss-of-function SGCD (delta-sarcoglycan) variants. Delta-sarcoglycan co-folds with beta- and gamma-sarcoglycan to form the core of the extracellular subcomplex, so its recessive loss is highly disruptive to assembly of the whole complex. The least frequent and most severe sarcoglycanopathy subtype (considered ultra-rare): in the largest reported international cohort (23 patients from 18 families), 87% had consanguineous parents, distal weakness appeared early in over half of patients, and 60% were wheelchair-bound from the early teens (median age 12 years). Note: separate, rare dominant-negative missense SGCD variants cause isolated familial dilated cardiomyopathy without skeletal myopathy — a mechanistically and clinically distinct entity from recessive LGMDR6 (see the discussion below).

Show evidence (2 references)

PMID:26709803 SUPPORT Other

"During assembly, beta-sarcoglycan tightly associates with delta-sarcoglycan to form a functional core that then recruits gamma- and alpha-sarcoglycan to form the sarcoglycan complex."

Establishes delta-sarcoglycan's central, early role in sarcoglycan subcomplex assembly, explaining why its recessive loss is disruptive to the whole complex.

PMID:34515763 SUPPORT Human Clinical

"Eighty-seven per cent of the patients had consanguineous parents. Ninety-one per cent of the patients were symptomatic at the time of the analysis. Proximal muscle weakness of the upper and lower limbs was the most common presenting symptom. Distal muscle weakness was observed early over the..."

The largest reported delta-sarcoglycanopathy (LGMDR6) cohort quantifies its consanguinity rate, distal-weakness pattern, cardiac and respiratory involvement, and severe rate of ambulation loss.

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Discussions and Knowledge Gaps

1

Should evidence for dominant-negative SGCD missense variants causing isolated familial dilated cardiomyopathy be used to support the pathophysiology of recessive LGMDR6 (delta-sarcoglycanopathy)?

INTERPRETATION RESOLVED sgcd-recessive-vs-dominant-cardiomyopathy

Attached to

has_subtypes#SGCD

Delta-sarcoglycan is essential for both skeletal and cardiac dystrophin-glycoprotein complex stability, but two distinct SGCD mutation classes produce clinically distinct diseases: biallelic loss-of-function variants cause recessive LGMDR6 (this entry, with skeletal myopathy plus variable cardiac involvement), while rare heterozygous dominant-negative missense variants (e.g., R71T, R97Q) cause isolated familial dilated cardiomyopathy without skeletal myopathy, by destabilizing cardiac myocyte membrane mechanics without perturbing overall DGC assembly. This entry cites the dominant-negative mechanism only as background evidence for delta-sarcoglycan's general importance to cardiac membrane stability, and does not use it as direct evidence for the recessive LGMDR6 cardiac phenotype.

Resolution: Scoped SGCD subtype description and evidence to the recessive loss-of-function mechanism only; the dominant DCM mechanism is documented here for context but is out of scope for this entry.

Show evidence (1 reference)

PMID:26968544 SUPPORT In Vitro

"While recessive mutations in δ-sarcoglycan cause limb girdle muscular dystrophy 2F, dominant mutations in δ-sarcoglycan have been linked to inherited dilated cardiomyopathy (DCM)."

The paper itself distinguishes the recessive LGMD2F (LGMDR6) allele class curated in this entry from the separate dominant DCM-causing allele class it studies, supporting the scoping decision above.

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Pathophysiology

5

Sarcoglycan-Sarcospan Subcomplex Assembly at the Sarcolemma

Alpha-, beta-, gamma-, and delta-sarcoglycan co-assemble with sarcospan into a subcomplex of the dystrophin-glycoprotein complex (DGC). A 2025 cryo-EM structure of the native complex revised the earlier biochemical assembly model: beta-, gamma- and delta-sarcoglycan co-fold on the extracellular side to form a tower-like structure that provides binding sites for alpha-sarcoglycan and for dystroglycan, while in the transmembrane region the sarcoglycans and sarcospan flank and stabilize dystroglycan's single transmembrane helix rather than forming a separate subcomplex as earlier biochemical assembly models proposed. On the intracellular side, sarcoglycans and dystroglycan engage the dystrophin-dystrobrevin subcomplex through the ZZ domain of dystrophin, completing a continuous mechanical link across the sarcolemma between the extracellular matrix and the intracellular cytoskeleton.

skeletal muscle fiber CL:0008002

sarcoglycan complex GO:0016012 dystrophin-associated glycoprotein complex GO:0016010

sarcolemma GO:0042383

Downstream

Sarcoglycan Complex Loss and DGC Destabilization Biallelic loss-of-function variants in any one of the four sarcoglycan genes (SGCA, SGCB, SGCG, SGCD) prevents normal folding, trafficking, or membrane insertion of that subunit, which secondarily destabilizes and reduces the other three sarcoglycans and the whole DGC at the sarcolemma.

Show evidence (2 references)

PMID:39663450 SUPPORT In Vitro

"on the extracellular side, beta-, gamma- and delta-sarcoglycans co-fold to form a specialized, extracellular tower-like structure, which has a central role in complex assembly by providing binding sites for alpha-sarcoglycan and dystroglycan. In the transmembrane region, sarcoglycans and..."

High-resolution cryo-EM structure of the native mouse skeletal-muscle DGC establishes the current, revised model of sarcoglycan-sarcospan subcomplex assembly and its role linking dystroglycan to dystrophin.

PMID:26709803 SUPPORT Other

"In skeletal muscle, the dystrophin-associated glycoprotein complex forms a link between the actin cytoskeleton and the extracellular matrix that is critical for muscle integrity. Within this complex resides the sarcoglycan subcomplex, which consists of four transmembrane glycoproteins (alpha-,..."

Establishes the sarcoglycan subcomplex's place within the DGC and its general cytoskeleton-to-ECM linking role (the earlier biochemical model of assembly order that the 2025 cryo-EM structure above revised).

Sarcoglycan Complex Loss and DGC Destabilization

Loss of one sarcoglycan subunit impairs assembly of the sarcoglycan subcomplex; the other three sarcoglycans, which depend on the missing subunit for stable membrane insertion, are secondarily reduced. Because the sarcoglycan-sarcospan subcomplex flanks and stabilizes dystroglycan within the DGC, its loss destabilizes the mechanical linkage of the whole complex between the muscle-fiber cytoskeleton and the basement membrane. Two lesion classes converge on this loss: null/frameshift variants (about a third of reported alleles) abolish the protein outright, while the more common missense variants (about two-thirds) typically produce a misfolded sarcoglycan that is recognized and prematurely degraded by the endoplasmic-reticulum-associated degradation (ERAD) quality-control pathway before it ever reaches the sarcolemma.

skeletal muscle fiber CL:0008002

dystrophin-associated glycoprotein complex GO:0016010

Animal models

Sgcb-, Sgcg-, or Sgcd-null mouse (individual knockout) Mouse recapitulates Germline loss of the corresponding sarcoglycan subunit destabilizes the DGC, as in human disease.

Sgca-null mouse (knockout) Mouse recapitulates Sgca-null mice recapitulate loss-driven progressive skeletal-muscle dystrophy.

Missense sarcoglycan knock-in (KI) mouse Mouse fails to recapitulate Missense knock-in mice fail to develop any myopathic phenotype, despite missense variants being the most common human sarcoglycanopathy lesion class and the ERAD-mediated-degradation mechanism being demonstrated directly in a zebrafish missense model (see the sgcb/sgcd-null zebrafish model below).

δ-sarcoglycan-deficient Syrian hamster (naturally occurring) Syrian hamster (Mesocricetus auratus) recapitulates A naturally occurring loss-of-function delta-sarcoglycan deficiency, closely paralleling the human LGMDR6 genetic mechanism.

sgcb-/- and sgcd-/- zebrafish (CRISPR knockout) Zebrafish recapitulates The sgcd-/- knockout line was used to directly demonstrate that a missense delta-sarcoglycan variant is a substrate for ERAD, the specific molecular mechanism proposed for the missense lesion class in human sarcoglycanopathy.

Downstream

Contraction-Induced Sarcolemmal Membrane Damage A destabilized DGC can no longer transmit mechanical force across the sarcolemma, so the membrane can no longer withstand the stress of repeated muscle contraction.

Show evidence (4 references)

PMID:38713975 SUPPORT Human Clinical

"The mutations impair the assembly of a key structural complex, which normally protects the sarcolemma of striated muscle from contraction-derived stress."

States directly that sarcoglycan gene mutations impair assembly of the sarcoglycan/DGC structural complex, the shared upstream lesion across all four subtypes.

PMID:36816759 SUPPORT Model Organism

"Loss of functional γ-sarcoglycan protein in the dystrophin-associated protein complex destabilizes the sarcolemma, leading to eventual myofiber death."

A gamma-sarcoglycan-null mouse model directly demonstrates that loss of one sarcoglycan subunit destabilizes the DGC/sarcolemma.

PMID:37628888 SUPPORT Model Organism

"The δ-SG knockout line was further exploited to demonstrate that a δ-SG missense mutant is a substrate for endoplasmic-reticulum-associated degradation (ERAD), indicating premature degradation due to protein folding defects."

A delta-sarcoglycan knockout zebrafish model directly demonstrates that a missense sarcoglycan variant is degraded by ERAD before reaching the membrane, the specific mechanism for the missense lesion class.

+ 1 more reference

Contraction-Induced Sarcolemmal Membrane Damage

The intact sarcoglycan-DGC complex normally undergoes chemical modification in response to contraction and mechanically stabilizes the sarcolemma against contraction-induced stress. With the complex destabilized, contraction produces microtears and, as in dystrophinopathy, a fragile and leaky sarcolemma; this alters intracellular calcium homeostasis and can eventually lead to mitochondrial dysfunction, driving cycles of myofiber injury.

skeletal muscle fiber CL:0008002

calcium ion transport GO:0006816 ⚠ ABNORMAL

Downstream

Progressive Myofiber Degeneration Repeated contraction-induced membrane injury that outpaces repair and regeneration leads to myofiber necrosis and chronic inflammation.

Show evidence (3 references)

PMID:26709803 SUPPORT Other

"Once integrated, the sarcoglycan complex plays a pivotal role in mechanically stabilising the sarcolemma as well as the dystrophin-associated glycoprotein complex. Additionally, the sarcoglycan complex undergoes chemical modifications in response to muscle contractions, thereby transducing..."

Establishes the sarcoglycan complex's normal role in mechanically stabilizing the sarcolemma during contraction and transducing mechanical stress into a cellular signal, the process lost when the complex is destabilized.

PMID:38713975 SUPPORT Human Clinical

"The mutations impair the assembly of a key structural complex, which normally protects the sarcolemma of striated muscle from contraction-derived stress."

Confirms that the sarcoglycan complex's normal function is to protect the sarcolemma from contraction-derived stress, and that this is what fails in sarcoglycanopathy.

PMID:37628888 SUPPORT Other

"With the disruption of the SG-complex, it is thought that, like in DMD, the sarcolemma becomes fragile and leaky. This results in the subsequent alteration in the intracellular calcium homeostasis, which can eventually lead to mitochondrial dysfunction."

Directly supports the calcium-ion-transport disturbance and downstream mitochondrial-dysfunction risk asserted on this node. Evidence source is OTHER because this is a discussion-section statement of the general sarcoglycanopathy mechanism (by analogy to DMD), not this paper's own zebrafish experimental data.

Progressive Myofiber Degeneration

Repeated contraction-induced membrane injury outpaces repair. Macrophages debride necrotic fibers and support satellite-cell-mediated regeneration, but when the degenerative process is massive or advanced, muscle stem cells can no longer sustain repair, so contractile tissue is progressively lost.

skeletal muscle fiber CL:0008002 macrophage CL:0000235

muscle cell apoptotic process GO:0010657 ↑ INCREASED inflammatory response GO:0006954 ↑ INCREASED

Animal models

Sgcb-, Sgcg-, or Sgcd-null mouse (individual knockout) Mouse recapitulates Each knockout line develops progressive dystrophic changes in skeletal muscle.

sgcb-/- and sgcd-/- zebrafish (CRISPR knockout) Zebrafish recapitulates Adult sgcd-/- zebrafish develop severe skeletal-muscle impairment with contractile tissue partially replaced by fibrotic and adipose tissue, following an initially mild larval phenotype.

Downstream

Fibrofatty Replacement of Skeletal Muscle Exhaustion of regenerative capacity leaves damaged contractile tissue progressively replaced by fibrous and adipose tissue.

Show evidence (1 reference)

PMID:37628888 SUPPORT Model Organism

"when the degenerative process is massive or at an advanced stage, muscle stem cells are unable to sustain the muscle repair, and the contractile muscle is progressively replaced by fibrotic or adipose tissue"

A delta-sarcoglycan knockout zebrafish model directly demonstrates that once regenerative capacity is exhausted, contractile tissue is progressively lost and replaced by fibrous and adipose tissue.

Fibrofatty Replacement of Skeletal Muscle

Contractile muscle tissue that outpaces regenerative capacity is progressively replaced by fibrous and adipose tissue, producing calf pseudohypertrophy early and irreversible weakness later.

skeletal muscle fiber CL:0008002 fibroblast CL:0000057

Downstream

Progressive proximal muscle weakness Loss of functional contractile muscle mass and its replacement by fibrofatty tissue manifests clinically as progressive proximal limb-girdle weakness.

Calf muscle hypertrophy Fibrofatty replacement and reactive enlargement of the calf musculature produce calf pseudohypertrophy, a characteristic early sign of sarcoglycanopathy.

Show evidence (2 references)

PMID:37628888 SUPPORT Model Organism

"These data suggest a severe skeletal muscle impairment, where damaged contractile tissue was partially replaced by fibrotic and adipose tissue, as demonstrated by the histological and TEM analyses of one-year-old zebrafish."

Direct histological/ultrastructural demonstration of fibrofatty replacement of damaged contractile muscle in an adult sarcoglycan-null zebrafish model.

PMID:39174842 SUPPORT Human Clinical

"It appears in childhood by progressive weakness of pelvic and/or scapular girdle muscles and calf hypertrophy, with a wide range of clinical inter- and intra-familial clinical variability."

Documents calf hypertrophy and progressive proximal weakness, the clinical correlates of fibrofatty replacement, in alpha-sarcoglycanopathy.

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Histopathology

2

Necrosis and Regeneration (Dystrophic Changes)

Muscle biopsy shows the dystrophic pattern of fiber necrosis and regeneration characteristic of the limb-girdle muscular dystrophies, typically accompanied by elevated serum creatine kinase.

Show evidence (1 reference)

PMID:20301582 SUPPORT Human Clinical

"The limb-girdle muscular dystrophies typically show degeneration/regeneration (dystrophic changes) on muscle biopsy, which is usually associated with elevated serum creatine kinase concentration."

GeneReviews establishes the dystrophic degeneration/regeneration pattern on muscle biopsy as characteristic of the LGMDs, including sarcoglycanopathy.

Endomysial Fibrosis with Inflammatory Infiltrate FREQUENT

Muscle biopsy in a large delta-sarcoglycanopathy (LGMDR6) cohort showed increased fibrotic tissue and necrotic fibers as the most frequent features, with inflammatory infiltrates in a minority of biopsies.

Show evidence (1 reference)

PMID:34515763 SUPPORT Human Clinical

"Increase in the amount of fibrotic tissue and presence of necrotic muscle fibres were the most frequent features (64.3 and 50%, respectively). Inflammatory infiltrates were observed in 28.6% of biopsies"

Quantifies fibrosis, necrosis, and inflammatory infiltrate on muscle biopsy in a large delta-sarcoglycanopathy cohort.

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Pathograph

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

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Phenotypes

12

Cardiovascular 3

Cardiomyopathy FREQUENT Dilated cardiomyopathy HP:0001644

Show evidence (2 references)

PMID:33051934 SUPPORT Human Clinical

"Dilated cardiomyopathy occurred in all sarcoglycanopathy subtypes, especially in γ-SG patients (p = 0.01)."

A 100-patient multicenter cohort confirms cardiomyopathy occurs across all sarcoglycanopathy subtypes, most prominently in gamma-sarcoglycanopathy.

PMID:12868499 SUPPORT Human Clinical

"Given the age profile of the patients studied, the 50% cardiac involvement found in our LGMD2E patients is likely to be a conservative estimate."

Quantifies cardiac involvement in a beta-sarcoglycanopathy (LGMDR4) patient cohort.

Cardiomyopathy in gamma-sarcoglycanopathy FREQUENT Dilated cardiomyopathy HP:0001644

Show evidence (1 reference)

PMID:40757565 SUPPORT Human Clinical

"other frequent features are scoliosis (40%) cardiomyopathy (30%), respiratory deficiency (50-60%) and retractions (70%), which are frequently observed especially in advanced cases"

Quantifies cardiomyopathy frequency specifically in gamma-sarcoglycanopathy.

Cardiac arrhythmia HP:0011675

Show evidence (1 reference)

PMID:34515763 SUPPORT Human Clinical

"Cardiac involvement, defined as cardiomyopathy or heart rhythm abnormalities, was reported in five patients (23.8%) with a median age of diagnosis of 13.0 years (range 11–17). Dilated cardiomyopathies were present in three patients (60%) and heart rhythm abnormalities were present in two patients."

Documents heart rhythm abnormalities as a distinct component of cardiac involvement (alongside dilated cardiomyopathy) in a large delta-sarcoglycanopathy cohort.

Metabolism 1

Elevated serum creatine kinase Elevated circulating creatine kinase concentration HP:0003236

Show evidence (1 reference)

PMID:34404573 SUPPORT Human Clinical

"Patients present muscle hypertrophy, elevated CK, variable muscle weaknesses, and progressive loss of ambulation."

Documents elevated serum creatine kinase as a consistent finding across the sarcoglycanopathies.

Musculoskeletal 5

Respiratory insufficiency due to muscle weakness FREQUENT HP:0002747

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:40757565 SUPPORT Human Clinical

"other frequent features are scoliosis (40%) cardiomyopathy (30%), respiratory deficiency (50-60%) and retractions (70%), which are frequently observed especially in advanced cases"

Quantifies respiratory deficiency frequency in gamma-sarcoglycanopathy.

Scoliosis FREQUENT HP:0002650

Show evidence (1 reference)

PMID:40757565 SUPPORT Human Clinical

"other frequent features are scoliosis (40%) cardiomyopathy (30%), respiratory deficiency (50-60%) and retractions (70%), which are frequently observed especially in advanced cases"

Quantifies scoliosis frequency in gamma-sarcoglycanopathy.

Flexion contracture FREQUENT HP:0001371

Show evidence (1 reference)

PMID:40757565 SUPPORT Human Clinical

"other frequent features are scoliosis (40%) cardiomyopathy (30%), respiratory deficiency (50-60%) and retractions (70%), which are frequently observed especially in advanced cases"

Quantifies retraction/contracture frequency in gamma-sarcoglycanopathy.

Distal muscle weakness FREQUENT HP:0002460

Show evidence (1 reference)

PMID:34515763 SUPPORT Human Clinical

"Distal muscle weakness was observed early over the course of the disease in 56.5% of the patients."

The largest reported delta-sarcoglycanopathy cohort quantifies early distal muscle weakness in 56.5% of patients.

Respiratory insufficiency due to muscle weakness HP:0002747

Course: PROGRESSIVE

Show evidence (2 references)

PMID:25862795 SUPPORT Human Clinical

"Six patients had restrictive respiratory insufficiency requiring assisted ventilation (19%)."

Quantifies restrictive respiratory insufficiency requiring assisted ventilation in a 32-patient beta-sarcoglycanopathy (LGMDR4) cohort.

PMID:34515763 SUPPORT Human Clinical

"Four patients (17.4%) required non-invasive ventilation."

Quantifies non-invasive ventilation requirement in a large delta-sarcoglycanopathy (LGMDR6) cohort, confirming respiratory insufficiency is not confined to a single subtype.

Other 3

Progressive proximal muscle weakness VERY_FREQUENT Limb-girdle muscle weakness HP:0003325

Course: PROGRESSIVE

Show evidence (1 reference)

PMID:40757565 SUPPORT Human Clinical

"The most common symptoms are proximal limb-girdle muscle weakness or wasting (common in about 80-90% of cases)"

Quantifies proximal limb-girdle weakness as the most common feature of sarcoglycanopathy, occurring in 80-90% of cases.

Calf muscle hypertrophy HP:0008981

Show evidence (1 reference)

PMID:39174842 SUPPORT Human Clinical

"It appears in childhood by progressive weakness of pelvic and/or scapular girdle muscles and calf hypertrophy, with a wide range of clinical inter- and intra-familial clinical variability."

Documents calf hypertrophy as a presenting sign of alpha-sarcoglycanopathy.

Loss of ambulation VERY_FREQUENT HP:0002505

Show evidence (1 reference)

PMID:33051934 SUPPORT Human Clinical

"At mean follow-up of 22.9 years, 65.3% of patients were wheelchair-bound (66.7% α-SG, 67.3% γ-SG, 40% β-SG)."

Quantifies the rate of loss of ambulation across sarcoglycanopathy subtypes at long-term follow-up.

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Genetic Associations

4

SGCA (alpha-sarcoglycan / LGMDR3)

Gene: SGCA hgnc:10805

Show evidence (1 reference)

PMID:34404573 SUPPORT Human Clinical

"Four subtypes are known: LGMDR3, LGMDR4, LGMDR5 and LGMDR6, caused, respectively, by mutations in the SGCA, SGCB, SGCG and SGCD genes."

Establishes the one-to-one correspondence between the four sarcoglycan genes and the four LGMD-R subtypes.

SGCB (beta-sarcoglycan / LGMDR4)

Gene: SGCB hgnc:10806

Show evidence (1 reference)

PMID:39663450 SUPPORT In Vitro

"on the extracellular side, beta-, gamma- and delta-sarcoglycans co-fold to form a specialized, extracellular tower-like structure, which has a central role in complex assembly by providing binding sites for alpha-sarcoglycan and dystroglycan"

Cryo-EM structure of the native complex shows beta-sarcoglycan's central structural role in the extracellular tower that nucleates complex assembly.

SGCG (gamma-sarcoglycan / LGMDR5)

Gene: SGCG hgnc:10809

Show evidence (1 reference)

PMID:36816759 SUPPORT Model Organism

"Loss of functional γ-sarcoglycan protein in the dystrophin-associated protein complex destabilizes the sarcolemma, leading to eventual myofiber death."

A gamma-sarcoglycan knockout mouse study documents the direct mechanistic consequence of SGCG loss on sarcolemmal stability.

SGCD (delta-sarcoglycan / LGMDR6)

Gene: SGCD hgnc:10807

Show evidence (1 reference)

PMID:26709803 SUPPORT Other

"During assembly, beta-sarcoglycan tightly associates with delta-sarcoglycan to form a functional core that then recruits gamma- and alpha-sarcoglycan to form the sarcoglycan complex."

Establishes delta-sarcoglycan's central role in nucleating sarcoglycan subcomplex assembly.

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Medical Actions

7

Supportive care (physical therapy and rehabilitation)

Action: physical therapy Ontology label: Physical Therapy NCIT:C15302

No curative or disease-modifying therapy is currently approved for any sarcoglycanopathy subtype; management is supportive, centered on physical therapy, stretching, and mobility aids to preserve function and prevent contractures.

Show evidence (2 references)

PMID:38713975 SUPPORT Human Clinical

"There is currently no effective treatment available; however, both gene replacement strategy and small molecule-based approaches show great promise and have entered or are starting to enter clinical trials."

Confirms that no curative treatment currently exists for sarcoglycanopathy, underscoring the role of supportive management while disease-modifying approaches remain investigational.

PMID:20301582 SUPPORT Human Clinical

"physical therapy and stretching exercises to promote mobility and prevent contractures"

GeneReviews recommends physical therapy and stretching exercises as standard supportive management for limb-girdle muscular dystrophy, including sarcoglycanopathy.

Cardiorespiratory surveillance

Action: cardiac and respiratory surveillance Ontology label: Supportive Care NCIT:C15747

Regular cardiac (echocardiography/ECG) and pulmonary function monitoring are indicated given the substantial risk of dilated cardiomyopathy and restrictive respiratory insufficiency, particularly in beta-, gamma-, and delta-sarcoglycanopathy.

Show evidence (2 references)

PMID:12868499 SUPPORT Human Clinical

"Careful cardiac monitoring should be carried out in beta-sarcoglycanopathy patients who are at high risk of developing cardiomyopathy."

Directly recommends cardiac monitoring in beta-sarcoglycanopathy patients given their high risk of cardiomyopathy.

PMID:20301582 SUPPORT Human Clinical

"monitoring for cardiomyopathy in LGMD types with cardiac involvement"

GeneReviews lists monitoring for cardiomyopathy as standard management for LGMD types with cardiac involvement, including sarcoglycanopathy.

Guideline-directed heart failure pharmacotherapy for beta-sarcoglycanopathy cardiomyopathy

Action: Pharmacotherapy NCIT:C15986

Agent: ACE inhibitor NCIT:C247 beta-blocker NCIT:C29576

Standard heart-failure pharmacotherapy (ACE inhibitors and beta-adrenergic antagonists) is used to manage the sarcoglycanopathy-associated dilated cardiomyopathy once it develops, particularly in beta-sarcoglycanopathy (SGCB/LGMDR4) where cardiac involvement is common.

Show evidence (1 reference)

PMID:12868499 SUPPORT Human Clinical

"Careful cardiac monitoring should be carried out in beta-sarcoglycanopathy patients who are at high risk of developing cardiomyopathy."

Establishes the high risk of cardiomyopathy in beta-sarcoglycanopathy that underpins the standard heart-failure pharmacotherapy indication.

AAV beta-sarcoglycan gene replacement therapy (SGCB)

Action: gene therapy Ontology label: Gene Therapy NCIT:C15238

Bidridistrogene xeboparvovec (SRP-9003), an AAVrh74 vector delivering a codon-optimized SGCB transgene, produced robust dose-dependent beta-sarcoglycan expression (mean 36.2% and 62.1% of normal at Day 60 in low- and high-dose cohorts, respectively) and preliminary motor improvements maintained through 2 years in a 6-patient Phase 1/2 first-in-human trial, and has since progressed to a Phase 3 multinational trial (NCT06246513) for beta-sarcoglycanopathy.

Mechanism Target:

RESTORES Sarcoglycan Complex Loss and DGC Destabilization — AAVrh74-mediated SGCB gene transfer restores beta-sarcoglycan expression, directly addressing the missing subunit that destabilizes the sarcoglycan subcomplex and the DGC.

Show evidence (1 reference)

PMID:38177855 SUPPORT Human Clinical

"Robust SGCB expression was observed: Day 60 mean (s.d.) percentage of normal expression 36.2% (2.7%) in Cohort 1 and 62.1% (8.7%) in Cohort 2."

Directly demonstrates restoration of beta-sarcoglycan expression in human patients following AAV gene transfer.

Show evidence (2 references)

PMID:38177855 SUPPORT Human Clinical

"Robust SGCB expression was observed: Day 60 mean (s.d.) percentage of normal expression 36.2% (2.7%) in Cohort 1 and 62.1% (8.7%) in Cohort 2. Post hoc exploratory analysis showed preliminary motor improvements using the North Star Assessment for Limb-girdle Type Muscular Dystrophies maintained..."

Reports the interim Phase 1/2 first-in-human results for AAV beta-sarcoglycan gene replacement therapy, the direct clinical precursor to the Phase 3 trial cited above.

PMID:34404573 SUPPORT Human Clinical

"Therapeutic approaches include the strategy of gene replacement mediated by a vector derived from adeno-associated virus (AAV). Pre-clinical studies have shown detectable levels of SG proteins in the muscle, and some improvement in the phenotype, in animal models. Therapeutic trials in humans..."

Confirms AAV-mediated sarcoglycan gene replacement as an active therapeutic strategy across the sarcoglycanopathies generally.

Investigational small-molecule ERAD inhibition

Action: Pharmacotherapy NCIT:C15986

Misfolded missense sarcoglycan variants are degraded by the ER-associated degradation (ERAD) quality-control pathway before reaching the sarcolemma; pharmacologically inhibiting this proteolysis is proposed as a mutation-class-specific small-molecule therapeutic strategy to increase the amount of (partially functional) sarcoglycan that reaches the membrane.

Mechanism Target:

INHIBITS Sarcoglycan Complex Loss and DGC Destabilization — Inhibiting ERAD-mediated proteolysis of misfolded missense sarcoglycan is intended to make more of the (partially functional) protein available to reach the sarcolemma, partially counteracting complex loss for the missense lesion class.

Show evidence (1 reference)

PMID:40757565 SUPPORT Human Clinical

"The inhibition of this proteolysis makes these proteins more available to migrate to the sarcolemma and thus becomes a potential therapeutic objective"

States the ERAD-inhibition mechanism-of-action directly, linking the treatment to the sarcoglycan-complex-loss node it targets.

Show evidence (1 reference)

PMID:40757565 SUPPORT Human Clinical

"The residual altered proteins are destroyed by a proteolytic quality-control system or endoplasmic reticulum-associated degradation, ERAD. The inhibition of this proteolysis makes these proteins more available to migrate to the sarcolemma and thus becomes a potential therapeutic objective"

States the ERAD-inhibition therapeutic rationale directly, applicable to missense sarcoglycan variants across subtypes.

Investigational AAV gamma-sarcoglycan gene transfer (SGCG)

Action: gene therapy Ontology label: Gene Therapy NCIT:C15238

A self-complementary AAVrh74 vector (SRP-9005) carrying a codon-optimized human SGCG transgene restored sarcoglycan complex expression, muscle histopathology, and functional performance in a Sgcg-null mouse model, supporting translation to human gamma-sarcoglycanopathy. An AAV vector carrying human SGCG (ATA-200) has since entered a Phase 1 human trial (NCT05973630) in ambulant children with gamma-sarcoglycanopathy (LGMDR5).

Mechanism Target:

RESTORES Sarcoglycan Complex Loss and DGC Destabilization — AAV-mediated SGCG gene transfer restores gamma-sarcoglycan expression and reconstitutes the sarcoglycan complex.

Show evidence (1 reference)

PMID:36816759 SUPPORT Model Organism

"This study demonstrates successful systemic delivery of the hSGCG transgene in SGCG -/- mice, with functional protein expression, reconstitution of the sarcoglycan complex, and corresponding physiological and functional improvements, which will help establish a minimal effective dose for..."

Directly demonstrates reconstitution of the sarcoglycan complex following AAV-SGCG gene transfer in a mouse model.

Show evidence (2 references)

PMID:36816759 SUPPORT Model Organism

"This study demonstrates successful systemic delivery of the hSGCG transgene in SGCG -/- mice, with functional protein expression, reconstitution of the sarcoglycan complex, and corresponding physiological and functional improvements, which will help establish a minimal effective dose for..."

Preclinical mouse study establishing proof of principle for AAV gamma-sarcoglycan gene transfer, aimed at future clinical translation.

clinicaltrials:NCT05973630 SUPPORT Human Clinical

"The purpose of ATA-003-GSAR study is to evaluate the safety and tolerability of a single intravenous infusion of ATA-200 in pediatric patients with limb girdle muscular dystrophy type 2c/R5 (LGMD R5)."

Confirms an AAV-SGCG gene therapy (ATA-200) has entered human clinical trial, the translation from the mouse proof-of-concept study above.

Genetic counseling

Action: genetic counseling Ontology label: Genetic Counseling NCIT:C15240

Genetic counseling is essential for carrier identification, recurrence-risk assessment, and reproductive planning once the causal sarcoglycan gene has been identified by molecular testing.

Show evidence (1 reference)

PMID:20301582 SUPPORT Human Clinical

"If the causative pathogenic variant(s) have been identified in the family, prenatal testing for pregnancies at increased risk is possible."

GeneReviews directly states the reproductive-planning/prenatal-testing rationale for genetic counseling once the causal variant is known, replacing an earlier snippet that only supported the diagnostic prerequisite rather than counseling itself.

🔬

Diagnosis

2

Molecular genetic testing

Diagnosis is established by identifying biallelic pathogenic variants in one of the four sarcoglycan genes, typically via a targeted neuromuscular NGS gene panel, supported by muscle biopsy immunohistochemistry showing loss or marked reduction of all four sarcoglycans (secondary to loss of the causal subunit).

Show evidence (2 references)

PMID:34404573 SUPPORT Human Clinical

"The diagnosis is currently based on the molecular screening for these mutations."

Confirms molecular genetic screening as the current diagnostic standard for sarcoglycanopathy.

PMID:20301582 SUPPORT Human Clinical

"Biochemical testing (i.e., protein testing by immunostaining or immunblotting) performed on a muscle biopsy can establish the diagnosis of the following LGMD types: sarcoglycanopathy, calpainopathy, dysferlinopathy, and O-linked glycosylation defects (also known as dystroglycanopathy)."

GeneReviews establishes muscle-biopsy immunostaining/immunoblotting as a route to establishing the sarcoglycanopathy diagnosis, complementing molecular genetic screening.

Differential diagnosis - cognition is preserved

Cognitive/intellectual impairment has never been reported in sarcoglycanopathy; new gait difficulty in a cognitively normal child is consistent with sarcoglycanopathy (or another muscular dystrophy) and should prompt CK testing and molecular workup rather than a primary neurodevelopmental diagnosis.

Show evidence (1 reference)

PMID:37628888 SUPPORT Human Clinical

"Cognitive impairment has never been reported."

States directly that cognitive impairment is not a feature of sarcoglycanopathy.

📊

Prevalence

1

Worldwide

Unknown Ultra Rare

Figure is sarcoglycanopathies as a share of LGMD-R cases, not a population point-prevalence rate. No independently verifiable population point-prevalence figure was found for sarcoglycanopathy as a whole (a deep-research draft cited a beta-sarcoglycanopathy rate that could not be located in the cited paper's cached abstract and was therefore not used - see the PR description). Sarcoglycanopathies are consistently described as rare to ultra-rare, constituting an estimated 10-25% of LGMD-R cases overall, with delta-sarcoglycanopathy/LGMDR6 specifically the least frequent and most severe subtype.

Show evidence (1 reference)

PMID:34404573 SUPPORT Human Clinical

"Sarcoglycanopathies are the most severe forms of autosomal recessive limb-girdle muscular dystrophies (LGMDs), constituting about 10-25% of LGMDs."

Establishes sarcoglycanopathy's relative frequency among LGMD-R cases; a precise general-population prevalence figure was not independently verifiable.

🔬

Clinical Trials

5

NCT06246513 PHASE_III ACTIVE_NOT_RECRUITING

A Phase 3 multinational, open-label systemic gene-delivery study evaluating the safety and efficacy of a single systemic dose of SRP-9003 (bidridistrogene xeboparvovec), an AAVrh74 beta-sarcoglycan gene-transfer therapy, in ambulatory and non-ambulatory participants with beta-sarcoglycanopathy (LGMD2E/R4/SGCB).

Target Phenotypes: Limb-girdle muscle weakness HP:0003325

Show evidence (1 reference)

clinicaltrials:NCT06246513 SUPPORT

"This is a multicenter, global study of the effects of a single systemic dose of SRP-9003 on beta-sarcoglycan (β-SG) gene expression in participants with limb-girdle muscular dystrophy, type 2E/R4 (LGMD2E/R4)."

The trial summary confirms SRP-9003 is a systemic beta-sarcoglycan gene therapy in Phase 3 development for beta-sarcoglycanopathy.

NCT03652259 PHASE_I TERMINATED

The first-in-human, single-center, open-label systemic gene delivery study of SRP-9003 (bidridistrogene xeboparvovec) in participants with beta-sarcoglycanopathy (LGMD2E/R4); results reported at PMID:38177855 are the direct clinical precursor to the Phase 3 trial (NCT06246513) above.

Target Phenotypes: Limb-girdle muscle weakness HP:0003325

Show evidence (1 reference)

clinicaltrials:NCT03652259 SUPPORT

"The proposed clinical trial is the first-in-human, single-center, open-label, gene delivery study of SRP-9003 (bidridistrogene xeboparvovec) in participants with LGMD2E."

The trial summary confirms this is the first-in-human SRP-9003 study, the registration record for the PMID:38177855 Phase 1/2 results already cited under the AAV beta-sarcoglycan gene replacement treatment.

NCT05876780 PHASE_I ACTIVE_NOT_RECRUITING

A multicenter, open-label, single-dose systemic gene transfer study of SRP-9003 in both ambulatory and non-ambulatory participants with beta-sarcoglycanopathy (LGMD2E/R4), quantifying beta-sarcoglycan expression in skeletal muscle.

Target Phenotypes: Limb-girdle muscle weakness HP:0003325

Show evidence (1 reference)

clinicaltrials:NCT05876780 SUPPORT

"The primary purpose of this study is to evaluate the safety of SRP-9003 and to quantify expression of β-SG in the skeletal muscle of participants with limb-girdle muscular dystrophy, type 2E/R4 (LGMD2E/R4)."

The trial summary confirms this Phase 1 study evaluates SRP-9003 in both ambulatory and non-ambulatory beta-sarcoglycanopathy patients.

NCT05973630 PHASE_I ACTIVE_NOT_RECRUITING

ATA-200, an AAV vector carrying the human SGCG gene, in a Phase 1 open-label study of ambulant children with gamma-sarcoglycanopathy (LGMDR5) — the human trial that the AAV gamma-sarcoglycan gene transfer treatment (SRP-9005 mouse proof-of-concept) is cited against above.

Target Phenotypes: Limb-girdle muscle weakness HP:0003325

Show evidence (1 reference)

clinicaltrials:NCT05973630 SUPPORT

"The purpose of ATA-003-GSAR study is to evaluate the safety and tolerability of a single intravenous infusion of ATA-200 in pediatric patients with limb girdle muscular dystrophy type 2c/R5 (LGMD R5)."

The trial summary confirms ATA-200 is an AAV-SGCG gene therapy in human Phase 1 development for gamma-sarcoglycanopathy.

NCT04475926 NOT_APPLICABLE ACTIVE_NOT_RECRUITING

Journey: a global, multicenter, longitudinal natural-history study following participants with beta- (LGMD2E/R4), alpha- (LGMD2D/R3), and gamma-sarcoglycanopathy (LGMD2C/R5), alongside calpainopathy (LGMD2A/R1), tracking mobility and pulmonary function for up to 5 years.

Target Phenotypes: Limb-girdle muscle weakness HP:0003325

Show evidence (1 reference)

clinicaltrials:NCT04475926 SUPPORT

"This study will follow participants who are screened and confirmed with a genetic diagnosis of Limb-girdle muscular dystrophy type 2E (LGMD2E/R4), Limb-girdle muscular dystrophy type 2D (LGMD2D/R3), Limb-girdle muscular dystrophy type 2C (LGMD2C/R5), or Limb-girdle muscular dystrophy type 2A (LGMD2A/R1)."

Confirms this observational natural-history study enrolls three of the four sarcoglycanopathy subtypes (alongside the genetically distinct calpainopathy) to characterize disease progression.

🐁

Animal Models

5

Sgcb-, Sgcg-, or Sgcd-null mouse (individual knockout)

Individual knockout of any one of Sgcb, Sgcg, or Sgcd in mice produces progressive skeletal-muscle dystrophy and, unlike the Sgca-null mouse below, dilated or hypertrophic cardiomyopathy — mirroring the beta-, gamma-, and delta-sarcoglycanopathy pattern of substantial human cardiac involvement.

Species

Mouse

Genotype

Individual germline knockout of Sgcb, Sgcg, or Sgcd

Publication

PMID:37628888

Pathograph links

Sarcoglycan Complex Loss and DGC Destabilization recapitulates fidelity: moderate Germline loss of the corresponding sarcoglycan subunit destabilizes the DGC, as in human disease.

Show evidence (1 reference)

PMID:37628888 SUPPORT Model Organism

"All these KO animals present signs of progressive dystrophy in skeletal musculature, whereas dilated or hypertrophic cardiomyopathy develops in β- γ-, and δ-SG-, but not in α-SG-null mice"

Establishes that loss of the corresponding sarcoglycan subunit produces progressive dystrophy across these mouse lines.

Progressive Myofiber Degeneration recapitulates fidelity: moderate Each knockout line develops progressive dystrophic changes in skeletal muscle.

Show evidence (1 reference)

PMID:37628888 SUPPORT Model Organism

"All these KO animals present signs of progressive dystrophy in skeletal musculature, whereas dilated or hypertrophic cardiomyopathy develops in β- γ-, and δ-SG-, but not in α-SG-null mice"

States directly that all sarcoglycan-null mouse lines present progressive dystrophy in skeletal musculature.

Show evidence (1 reference)

PMID:37628888 SUPPORT Model Organism

"All these KO animals present signs of progressive dystrophy in skeletal musculature, whereas dilated or hypertrophic cardiomyopathy develops in β- γ-, and δ-SG-, but not in α-SG-null mice"

Summary statement (citing the primary mouse-model literature) of the shared skeletal phenotype and beta/gamma/delta-specific cardiac phenotype across the individual sarcoglycan-null mouse lines.

Sgca-null mouse (knockout)

Alpha-sarcoglycan-null mice develop progressive skeletal-muscle dystrophy but generally do not develop the cardiomyopathy seen in the other three sarcoglycan-null mouse lines, despite substantial cardiac involvement being documented in human alpha-sarcoglycanopathy (LGMDR3) patients.

Species

Mouse

Genotype

Sgca germline knockout

Publication

PMID:37628888

Pathograph links

Sarcoglycan Complex Loss and DGC Destabilization recapitulates fidelity: moderate Sgca-null mice recapitulate loss-driven progressive skeletal-muscle dystrophy.

Show evidence (1 reference)

PMID:37628888 SUPPORT Model Organism

"All these KO animals present signs of progressive dystrophy in skeletal musculature, whereas dilated or hypertrophic cardiomyopathy develops in β- γ-, and δ-SG-, but not in α-SG-null mice"

States that all sarcoglycan-null mouse lines, including Sgca-null, present progressive skeletal-muscle dystrophy.

Show evidence (1 reference)

PMID:37628888 SUPPORT Model Organism

"All these KO animals present signs of progressive dystrophy in skeletal musculature, whereas dilated or hypertrophic cardiomyopathy develops in β- γ-, and δ-SG-, but not in α-SG-null mice"

Directly states that alpha-sarcoglycan-null mice, unlike the other three sarcoglycan-null lines, generally do not develop cardiomyopathy.

Missense sarcoglycan knock-in (KI) mouse

Because missense mutations account for the majority (about two-thirds) of reported sarcoglycanopathy alleles, knock-in (KI) mice carrying a missense sarcoglycan variant would in principle be the more disease-relevant model class relative to null/knockout lines. However, the three sarcoglycan missense knock-in mouse lines generated to date have failed to develop a myopathic phenotype at all.

Species

Mouse

Genotype

Missense sarcoglycan knock-in (three independent lines generated to date)

Publication

PMID:37628888

Pathograph links

Sarcoglycan Complex Loss and DGC Destabilization fails to recapitulate fidelity: low Missense knock-in mice fail to develop any myopathic phenotype, despite missense variants being the most common human sarcoglycanopathy lesion class and the ERAD-mediated-degradation mechanism being demonstrated directly in a zebrafish missense model (see the sgcb/sgcd-null zebrafish model below).

Limitations: All three sarcoglycan missense knock-in mouse lines generated to date fail to develop a myopathic phenotype, unlike the null/knockout mouse lines — limiting mouse KI models' usefulness for studying the missense/ERAD lesion class that predominates in human patients, and motivating the zebrafish missense-modeling approach instead.

Show evidence (1 reference)

PMID:37628888 SUPPORT Model Organism

"we must consider that the three SG-KI mice, generated until now, failed to develop a myopathic phenotype"

Directly documents the negative result: existing missense knock-in mouse models do not reproduce a myopathic phenotype.

Show evidence (1 reference)

PMID:37628888 SUPPORT Model Organism

"we must consider that the three SG-KI mice, generated until now, failed to develop a myopathic phenotype"

States directly that all three missense sarcoglycan knock-in mouse lines generated to date fail to develop any myopathic phenotype.

δ-sarcoglycan-deficient Syrian hamster (naturally occurring)

Naturally occurring delta-sarcoglycan-deficient hamster strains develop both skeletal myopathy and cardiomyopathy resembling human delta-sarcoglycanopathy (LGMDR6), and are considered one of the two animal-model classes (with sarcoglycan-knockout mice) that best mimic human sarcoglycanopathy.

Species

Syrian hamster (Mesocricetus auratus)

Genotype

Naturally occurring delta-sarcoglycan deficiency

Publication

PMID:37628888

Pathograph links

Sarcoglycan Complex Loss and DGC Destabilization recapitulates fidelity: high A naturally occurring loss-of-function delta-sarcoglycan deficiency, closely paralleling the human LGMDR6 genetic mechanism.

Show evidence (1 reference)

PMID:37628888 SUPPORT Model Organism

"Currently, the animal models that best mimic sarcoglycanopathies are SG-KO mice and the naturally occurring δ-SG mutants identified in several hamster strains. They develop muscle and heart problems, as in humans"

Identifies the naturally occurring hamster delta-sarcoglycan deficiency as one of the two best-mimicking animal-model classes.

Show evidence (1 reference)

PMID:37628888 SUPPORT Model Organism

"Currently, the animal models that best mimic sarcoglycanopathies are SG-KO mice and the naturally occurring δ-SG mutants identified in several hamster strains. They develop muscle and heart problems, as in humans"

States directly that naturally occurring delta-sarcoglycan-deficient hamster strains develop both muscle and heart problems mirroring human disease.

sgcb-/- and sgcd-/- zebrafish (CRISPR knockout)

CRISPR/Cas9 knockout zebrafish lines for sgcb and sgcd show a mild larval phenotype that progresses to adult dystrophic skeletal muscle and cardiomyopathy, and the sgcd-/- line was used to directly demonstrate ERAD-mediated degradation of a missense delta-sarcoglycan variant.

Species

Zebrafish

Genotype

CRISPR/Cas9-induced exon 2 frameshift null alleles of sgcb and sgcd (independent lines); the sgcd-/- line was characterized in most detail

Publication

PMID:37628888

Pathograph links

Sarcoglycan Complex Loss and DGC Destabilization recapitulates fidelity: high The sgcd-/- knockout line was used to directly demonstrate that a missense delta-sarcoglycan variant is a substrate for ERAD, the specific molecular mechanism proposed for the missense lesion class in human sarcoglycanopathy.

Show evidence (1 reference)

PMID:37628888 SUPPORT Model Organism

"The δ-SG knockout line was further exploited to demonstrate that a δ-SG missense mutant is a substrate for endoplasmic-reticulum-associated degradation (ERAD), indicating premature degradation due to protein folding defects."

Direct experimental demonstration of ERAD-mediated degradation of a missense sarcoglycan variant in this zebrafish model.

Progressive Myofiber Degeneration recapitulates fidelity: moderate Adult sgcd-/- zebrafish develop severe skeletal-muscle impairment with contractile tissue partially replaced by fibrotic and adipose tissue, following an initially mild larval phenotype.

Limitations: The overt dystrophic phenotype emerges only in adulthood; larval-stage zebrafish show minimal muscle damage despite complete loss of sarcoglycan protein, so early-life screening in this model would under-detect the phenotype.

Show evidence (1 reference)

PMID:37628888 SUPPORT Model Organism

"These data suggest a severe skeletal muscle impairment, where damaged contractile tissue was partially replaced by fibrotic and adipose tissue, as demonstrated by the histological and TEM analyses of one-year-old zebrafish."

Direct histological/ultrastructural demonstration of progressive myofiber degeneration and fibrofatty replacement in adult sgcd-/- zebrafish.

Show evidence (1 reference)

PMID:37628888 SUPPORT Model Organism

"we observed clear signs of dystrophy and cardiomyopathy, well-resembling the human condition"

Direct primary-data statement that adult sarcoglycan-null zebrafish recapitulate both the dystrophic and cardiac features of human sarcoglycanopathy.

{ }

Source YAML

click to show

name: Sarcoglycanopathy
creation_date: "2026-08-26T00:00:00Z"
category: Mendelian
synonyms:
- qualitative or quantitative defects of sarcoglycan
- sarcoglycan-deficient limb-girdle muscular dystrophy
- LGMD R3-R6
description: >-
  Sarcoglycanopathy is the mechanistically coherent subgroup of autosomal
  recessive limb-girdle muscular dystrophy (LGMD-R) caused by biallelic
  loss-of-function variants in one of the four sarcoglycan genes (SGCA, SGCB,
  SGCG, SGCD). The sarcoglycans co-assemble with sarcospan into a subcomplex
  of the dystrophin-glycoprotein complex (DGC) at the sarcolemma; loss of any
  one subunit destabilizes assembly and trafficking of the whole subcomplex,
  and secondarily reduces the other three sarcoglycans, undermining the DGC's
  mechanical linkage between the myofiber cytoskeleton and the extracellular
  matrix. The shared downstream consequence is a sarcolemma that cannot
  withstand contraction-induced mechanical stress, producing progressive
  myofiber degeneration, elevated serum creatine kinase, proximal
  limb-girdle weakness with calf hypertrophy, and, in a substantial fraction
  of patients, cardiac and respiratory muscle involvement. The four
  gene-defined forms (alpha/LGMDR3/SGCA, beta/LGMDR4/SGCB, gamma/LGMDR5/SGCG,
  delta/LGMDR6/SGCD) are together the most severe forms of LGMD-R, accounting
  for roughly 10-25% of LGMD cases overall, with usual onset in the first
  decade of life.

  This entry sits *below* `Autosomal_Recessive_Limb-Girdle_Muscular_Dystrophy`
  (MONDO:0015152), which is the broader LGMD-R root spanning genetically and
  mechanistically distinct causes (sarcolemmal repair failure in DYSF, a
  calcium-activated protease in CAPN3, alpha-dystroglycan glycosylation in
  FKRP). It captures specifically the sarcoglycan-complex/DGC-destabilization
  mechanism shared by SGCA/SGCB/SGCG/SGCD, matching MONDO's own class
  structure: MONDO:0016140 (sarcoglycanopathy) has four exact-child terms
  (MONDO:0016141-0016144, "qualitative or quantitative defects of
  alpha/beta/gamma/delta-sarcoglycan"), and each corresponding clinical LGMD
  subtype term (e.g. MONDO:0011968, LGMD type 2D) is multiply classified
  under both this term and MONDO:0015152. See the modeling-decision note
  below and the PR description for the lump-vs-split rationale.
disease_term:
  preferred_term: sarcoglycanopathy
  term:
    id: MONDO:0016140
    label: sarcoglycanopathy
parents:
- Autosomal Recessive Limb-Girdle Muscular Dystrophy
- Limb-Girdle Muscular Dystrophy
- Muscular Dystrophy
- Neuromuscular Disease

inheritance:
- name: Autosomal recessive
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  description: >-
    All four sarcoglycanopathy subtypes are inherited in an autosomal
    recessive manner; affected individuals carry biallelic pathogenic
    variants in a single sarcoglycan gene (compound heterozygosity across
    different sarcoglycan genes does not cause disease).
  evidence:
  - reference: PMID:34404573
    reference_title: "Sarcoglycanopathies: an update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Sarcoglycanopathies are the most severe forms of autosomal recessive
      limb-girdle muscular dystrophies (LGMDs), constituting about 10-25% of
      LGMDs.
    explanation: >-
      Establishes autosomal recessive inheritance and the overall severity
      and relative frequency of the sarcoglycanopathies among LGMDs.

references:
- reference: PMID:20301582
  title: "Limb-Girdle Muscular Dystrophy Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
  tags:
  - GeneReviews

has_subtypes:
- name: SGCA
  display_name: LGMD R3 / alpha-sarcoglycanopathy (LGMD2D; SGCA)
  subtype_term:
    preferred_term: autosomal recessive limb-girdle muscular dystrophy type 2D
    term:
      id: MONDO:0011968
      label: autosomal recessive limb-girdle muscular dystrophy type 2D
  description: >-
    Caused by biallelic SGCA (alpha-sarcoglycan, 17q21.33) variants. Presents
    in childhood with progressive weakness of the pelvic and/or scapular
    girdle muscles and calf hypertrophy, with wide inter- and intra-familial
    clinical variability. Alpha-sarcoglycan is added to the sarcoglycan
    subcomplex last during assembly, docking onto the beta/gamma/delta core.
    In a large multicenter cohort, mean age at onset was 8 years (later than
    gamma-sarcoglycanopathy) and 66.7% of patients were wheelchair-bound at
    mean 22.9-year follow-up.
  genes:
  - preferred_term: SGCA
    term:
      id: hgnc:10805
      label: SGCA
  evidence:
  - reference: PMID:39174842
    reference_title: "Molecular diagnosis of Alpha-sarcoglycanopathies by NGS in seven Moroccan families and report of two novel variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Limb-girdle muscular dystrophy by alpha-sarcoglycan deficiency or LGMD
      R3 alpha-sarcoglycan-related is a subtype of the autosomal recessive
      sarcoglycanopathies caused by variants in the alpha-sarcoglycan gene
      (SGCA) at 17q21.33. It appears in childhood by progressive weakness of
      pelvic and/or scapular girdle muscles and calf hypertrophy, with a
      wide range of clinical inter- and intra-familial clinical variability.
    explanation: >-
      Confirms SGCA as the causal gene and documents the characteristic
      childhood-onset presentation of alpha-sarcoglycanopathy.
  - reference: PMID:33051934
    reference_title: "Clinical correlations and long-term follow-up in 100 patients with sarcoglycanopathies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The γ-SG patients had earlier disease onset than α-SG patients (5.5
      vs. 8 years; p = 0.022) and β-SG patients (24.4 years).
    explanation: >-
      A 100-patient multicenter cohort quantifies alpha-sarcoglycanopathy
      onset age relative to the other subtypes.
- name: SGCB
  display_name: LGMD R4 / beta-sarcoglycanopathy (LGMD2E; SGCB)
  subtype_term:
    preferred_term: autosomal recessive limb-girdle muscular dystrophy type 2E
    term:
      id: MONDO:0011423
      label: autosomal recessive limb-girdle muscular dystrophy type 2E
  description: >-
    Caused by biallelic SGCB (beta-sarcoglycan) variants. Beta-sarcoglycan
    co-folds with delta- and gamma-sarcoglycan to form the extracellular
    core of the subcomplex, so its loss is particularly disruptive to
    complex assembly. Clinically heterogeneous (often, but not always,
    severe childhood-onset disease; mean onset around 24 years in one
    multicenter series). Cardiac involvement is common, reported in 63% of
    a 32-patient cohort, often preceding overt skeletal muscle weakness;
    19% required assisted ventilation for restrictive respiratory
    insufficiency. First-in-human systemic AAV gene replacement therapy has
    reached Phase 3 (see Treatments).
  genes:
  - preferred_term: SGCB
    term:
      id: hgnc:10806
      label: SGCB
  evidence:
  - reference: PMID:25862795
    reference_title: "Clinical and genetic spectrum in limb-girdle muscular dystrophy type 2E."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Cardiac involvement was observed in 20 patients (63%) even before
      overt muscle involvement. Six patients had restrictive respiratory
      insufficiency requiring assisted ventilation (19%).
    explanation: >-
      Quantifies cardiac and respiratory involvement in a 32-patient
      beta-sarcoglycanopathy (LGMDR4) cohort.
  - reference: PMID:12868499
    reference_title: "LGMD2E patients risk developing dilated cardiomyopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Given the age profile of the patients studied, the 50% cardiac
      involvement found in our LGMD2E patients is likely to be a
      conservative estimate. Careful cardiac monitoring should be carried
      out in beta-sarcoglycanopathy patients who are at high risk of
      developing cardiomyopathy.
    explanation: >-
      An earlier, smaller cohort independently documents high cardiac
      involvement in beta-sarcoglycanopathy/LGMDR4 and establishes the need
      for cardiac surveillance.
- name: SGCG
  display_name: LGMD R5 / gamma-sarcoglycanopathy (LGMD2C; SGCG)
  subtype_term:
    preferred_term: autosomal recessive limb-girdle muscular dystrophy type 2C
    term:
      id: MONDO:0009677
      label: autosomal recessive limb-girdle muscular dystrophy type 2C
  description: >-
    Caused by biallelic SGCG (gamma-sarcoglycan, 13q12.12) variants. The
    first sarcoglycanopathy to be molecularly characterized, and typically
    the earliest-onset and most severe subtype (mean onset 5.5 years in a
    100-patient cohort, versus 8 years for alpha- and 24.4 years for
    beta-sarcoglycanopathy). Shows strong founder effects in specific
    populations (>90% of patients homozygous for c.525delT in a French
    multicenter series; a near-exclusive c.521del founder mutation in
    Tunisia, historically called "Severe Childhood Autosomal Recessive
    Muscular Dystrophy"/Tunisian Muscular Dystrophy; a separate C283Y
    founder mutation in Roma/Gypsy populations across Europe). Frequently
    Duchenne-like in severity, with high rates of scoliosis, respiratory
    deficiency, and cardiomyopathy.
  genes:
  - preferred_term: SGCG
    term:
      id: hgnc:10809
      label: SGCG
  evidence:
  - reference: PMID:40757565
    reference_title: "An Update of Clinical, Epidemiological, and Psychosocial Features in Gamma-Sarcoglycanopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The most common symptoms are proximal limb-girdle muscle weakness or
      wasting (common in about 80-90% of cases); other frequent features are
      scoliosis (40%) cardiomyopathy (30%), respiratory deficiency (50-60%)
      and retractions (70%), which are frequently observed especially in
      advanced cases.
    explanation: >-
      Quantifies the frequency of the major clinical features of
      gamma-sarcoglycanopathy/LGMDR5 in a contemporary case series and
      literature review.
  - reference: PMID:15479193
    reference_title: "C283Y gamma-sarcoglycan gene mutation in the Bulgarian Roma (Gypsy) population: prevalence study and carrier screening in a high-risk community."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Limb-girdle muscular dystrophy type 2C (LGMD2C) is caused by mutations
      in the gamma-sarcoglycan gene where a founder Gypsy mutation C283Y was
      detected. The Bulgarian Gypsy LGMD2C patients, as the Gypsy patients
      from other countries, were found to be homozygous for this mutation.
    explanation: >-
      Documents the C283Y founder mutation and its high carrier frequency in
      Roma/Gypsy populations, a distinctive epidemiological feature of
      gamma-sarcoglycanopathy.
  - reference: PMID:33051934
    reference_title: "Clinical correlations and long-term follow-up in 100 patients with sarcoglycanopathies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The α-SG patients showed genetic heterogeneity, whereas >90% of γ-SG
      patients carried the homozygous c.525delT frameshift variant.
    explanation: >-
      Documents a second, independent gamma-sarcoglycan founder mutation
      (c.525delT) in a French multicenter cohort, distinct from the C283Y
      and c.521del founder alleles above.
- name: SGCD
  display_name: LGMD R6 / delta-sarcoglycanopathy (LGMD2F; SGCD)
  subtype_term:
    preferred_term: autosomal recessive limb-girdle muscular dystrophy type 2F
    term:
      id: MONDO:0011028
      label: autosomal recessive limb-girdle muscular dystrophy type 2F
  description: >-
    Caused by biallelic loss-of-function SGCD (delta-sarcoglycan) variants.
    Delta-sarcoglycan co-folds with beta- and gamma-sarcoglycan to form the
    core of the extracellular subcomplex, so its recessive loss is highly
    disruptive to assembly of the whole complex. The least frequent and
    most severe sarcoglycanopathy subtype (considered ultra-rare): in the
    largest reported international cohort (23 patients from 18 families),
    87% had consanguineous parents, distal weakness appeared early in over
    half of patients, and 60% were wheelchair-bound from the early teens
    (median age 12 years). Note: separate, rare dominant-negative missense
    SGCD variants cause isolated familial dilated cardiomyopathy without
    skeletal myopathy — a mechanistically and clinically distinct entity
    from recessive LGMDR6 (see the discussion below).
  genes:
  - preferred_term: SGCD
    term:
      id: hgnc:10807
      label: SGCD
  evidence:
  - reference: PMID:26709803
    reference_title: "The sarcoglycan complex in skeletal muscle."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      During assembly, beta-sarcoglycan tightly associates with
      delta-sarcoglycan to form a functional core that then recruits gamma-
      and alpha-sarcoglycan to form the sarcoglycan complex.
    explanation: >-
      Establishes delta-sarcoglycan's central, early role in sarcoglycan
      subcomplex assembly, explaining why its recessive loss is disruptive
      to the whole complex.
  - reference: PMID:34515763
    reference_title: "Clinical and genetic spectrum of a large cohort of patients with δ-sarcoglycan muscular dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Eighty-seven per cent of the patients had consanguineous parents.
      Ninety-one per cent of the patients were symptomatic at the time of
      the analysis. Proximal muscle weakness of the upper and lower limbs
      was the most common presenting symptom. Distal muscle weakness was
      observed early over the course of the disease in 56.5% of the
      patients. Cardiac involvement was reported in five patients (21.7%)
      and four patients (17.4%) required non-invasive ventilation. Sixty
      per cent of patients were wheelchair-bound since early teens (median
      age of 12.0 years).
    explanation: >-
      The largest reported delta-sarcoglycanopathy (LGMDR6) cohort
      quantifies its consanguinity rate, distal-weakness pattern, cardiac
      and respiratory involvement, and severe rate of ambulation loss.

genetic:
- name: SGCA (alpha-sarcoglycan / LGMDR3)
  subtype: SGCA
  gene_term:
    preferred_term: SGCA
    term:
      id: hgnc:10805
      label: SGCA
  notes: >-
    SGCA encodes alpha-sarcoglycan, a type I transmembrane glycoprotein
    docked onto the beta/gamma/delta-sarcoglycan core of the sarcoglycan
    subcomplex within the dystrophin-glycoprotein complex.
  case_fractions:
  - population: French multicenter cohort (4 Paris-area centers)
    case_fraction_percent: 41.0
    cohort_size: 100
    notes: >-
      41 of 100 sarcoglycanopathy patients (alpha, beta, and gamma subtypes
      only; no delta-sarcoglycanopathy patients in this series).
    evidence:
    - reference: PMID:33051934
      reference_title: "Clinical correlations and long-term follow-up in 100 patients with sarcoglycanopathies."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        One hundred patients (54 γ-SG; 41 α-SG; 5 β-SG) from 80 families
        were included.
      explanation: >-
        Directly reports the alpha-sarcoglycanopathy case count in this
        100-patient multicenter cohort.
  evidence:
  - reference: PMID:34404573
    reference_title: "Sarcoglycanopathies: an update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Four subtypes are known: LGMDR3, LGMDR4, LGMDR5 and LGMDR6, caused,
      respectively, by mutations in the SGCA, SGCB, SGCG and SGCD genes.
    explanation: >-
      Establishes the one-to-one correspondence between the four
      sarcoglycan genes and the four LGMD-R subtypes.
- name: SGCB (beta-sarcoglycan / LGMDR4)
  subtype: SGCB
  gene_term:
    preferred_term: SGCB
    term:
      id: hgnc:10806
      label: SGCB
  notes: >-
    SGCB encodes beta-sarcoglycan, which co-folds with delta- and
    gamma-sarcoglycan to form the extracellular core of the sarcoglycan
    subcomplex.
  case_fractions:
  - population: French multicenter cohort (4 Paris-area centers)
    case_fraction_percent: 5.0
    cohort_size: 100
    notes: >-
      5 of 100 sarcoglycanopathy patients (alpha, beta, and gamma subtypes
      only; no delta-sarcoglycanopathy patients in this series). The
      smallest of the three subgroups in this cohort.
    evidence:
    - reference: PMID:33051934
      reference_title: "Clinical correlations and long-term follow-up in 100 patients with sarcoglycanopathies."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        One hundred patients (54 γ-SG; 41 α-SG; 5 β-SG) from 80 families
        were included.
      explanation: >-
        Directly reports the beta-sarcoglycanopathy case count in this
        100-patient multicenter cohort.
  evidence:
  - reference: PMID:39663450
    reference_title: "Structure and assembly of the dystrophin glycoprotein complex."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      on the extracellular side, beta-, gamma- and delta-sarcoglycans
      co-fold to form a specialized, extracellular tower-like structure,
      which has a central role in complex assembly by providing binding
      sites for alpha-sarcoglycan and dystroglycan
    explanation: >-
      Cryo-EM structure of the native complex shows beta-sarcoglycan's
      central structural role in the extracellular tower that nucleates
      complex assembly.
- name: SGCG (gamma-sarcoglycan / LGMDR5)
  subtype: SGCG
  gene_term:
    preferred_term: SGCG
    term:
      id: hgnc:10809
      label: SGCG
  notes: >-
    SGCG encodes gamma-sarcoglycan; loss of functional gamma-sarcoglycan
    protein in the dystrophin-associated protein complex destabilizes the
    sarcolemma.
  case_fractions:
  - population: French multicenter cohort (4 Paris-area centers)
    case_fraction_percent: 54.0
    cohort_size: 100
    notes: >-
      54 of 100 sarcoglycanopathy patients (alpha, beta, and gamma subtypes
      only; no delta-sarcoglycanopathy patients in this series). The
      largest of the three subgroups in this cohort.
    evidence:
    - reference: PMID:33051934
      reference_title: "Clinical correlations and long-term follow-up in 100 patients with sarcoglycanopathies."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        One hundred patients (54 γ-SG; 41 α-SG; 5 β-SG) from 80 families
        were included.
      explanation: >-
        Directly reports the gamma-sarcoglycanopathy case count in this
        100-patient multicenter cohort.
  evidence:
  - reference: PMID:36816759
    reference_title: "Systemic γ-sarcoglycan AAV gene transfer results in dose-dependent correction of muscle deficits in the LGMD 2C/R5 mouse model."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Loss of functional γ-sarcoglycan protein in the dystrophin-associated
      protein complex destabilizes the sarcolemma, leading to eventual
      myofiber death.
    explanation: >-
      A gamma-sarcoglycan knockout mouse study documents the direct
      mechanistic consequence of SGCG loss on sarcolemmal stability.
- name: SGCD (delta-sarcoglycan / LGMDR6)
  subtype: SGCD
  gene_term:
    preferred_term: SGCD
    term:
      id: hgnc:10807
      label: SGCD
  notes: >-
    SGCD encodes delta-sarcoglycan, which co-folds with beta- and
    gamma-sarcoglycan to form the extracellular core of the sarcoglycan
    subcomplex; recessive loss-of-function variants cause LGMDR6, distinct
    from the rare dominant-negative SGCD missense variants that cause
    isolated familial dilated cardiomyopathy.
  evidence:
  - reference: PMID:26709803
    reference_title: "The sarcoglycan complex in skeletal muscle."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      During assembly, beta-sarcoglycan tightly associates with
      delta-sarcoglycan to form a functional core that then recruits gamma-
      and alpha-sarcoglycan to form the sarcoglycan complex.
    explanation: >-
      Establishes delta-sarcoglycan's central role in nucleating sarcoglycan
      subcomplex assembly.

pathophysiology:
- name: Sarcoglycan-Sarcospan Subcomplex Assembly at the Sarcolemma
  biological_scale: MOLECULAR
  description: >-
    Alpha-, beta-, gamma-, and delta-sarcoglycan co-assemble with sarcospan
    into a subcomplex of the dystrophin-glycoprotein complex (DGC). A 2025
    cryo-EM structure of the native complex revised the earlier
    biochemical assembly model: beta-, gamma- and delta-sarcoglycan co-fold
    on the extracellular side to form a tower-like structure that provides
    binding sites for alpha-sarcoglycan and for dystroglycan, while in the
    transmembrane region the sarcoglycans and sarcospan flank and stabilize
    dystroglycan's single transmembrane helix rather than forming a
    separate subcomplex as earlier biochemical assembly models proposed.
    On the intracellular side, sarcoglycans and dystroglycan engage the
    dystrophin-dystrobrevin subcomplex through the ZZ domain of dystrophin,
    completing a continuous mechanical link across the sarcolemma between
    the extracellular matrix and the intracellular cytoskeleton.
  protein_complexes:
  - preferred_term: sarcoglycan complex
    term:
      id: GO:0016012
      label: sarcoglycan complex
  - preferred_term: dystrophin-associated glycoprotein complex
    term:
      id: GO:0016010
      label: dystrophin-associated glycoprotein complex
  cellular_components:
  - preferred_term: sarcolemma
    term:
      id: GO:0042383
      label: sarcolemma
  cell_types:
  - preferred_term: skeletal muscle fiber
    term:
      id: CL:0008002
      label: skeletal muscle fiber
  evidence:
  - reference: PMID:39663450
    reference_title: "Structure and assembly of the dystrophin glycoprotein complex."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      on the extracellular side, beta-, gamma- and delta-sarcoglycans
      co-fold to form a specialized, extracellular tower-like structure,
      which has a central role in complex assembly by providing binding
      sites for alpha-sarcoglycan and dystroglycan. In the transmembrane
      region, sarcoglycans and sarcospan flank and stabilize the single
      transmembrane helix of dystroglycan, rather than forming a subcomplex
      as previously proposed
    explanation: >-
      High-resolution cryo-EM structure of the native mouse skeletal-muscle
      DGC establishes the current, revised model of sarcoglycan-sarcospan
      subcomplex assembly and its role linking dystroglycan to dystrophin.
  - reference: PMID:26709803
    reference_title: "The sarcoglycan complex in skeletal muscle."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      In skeletal muscle, the dystrophin-associated glycoprotein complex
      forms a link between the actin cytoskeleton and the extracellular
      matrix that is critical for muscle integrity. Within this complex
      resides the sarcoglycan subcomplex, which consists of four
      transmembrane glycoproteins (alpha-, beta-, gamma-, and
      delta-sarcoglycan).
    explanation: >-
      Establishes the sarcoglycan subcomplex's place within the DGC and its
      general cytoskeleton-to-ECM linking role (the earlier biochemical
      model of assembly order that the 2025 cryo-EM structure above
      revised).
  downstream:
  - target: Sarcoglycan Complex Loss and DGC Destabilization
    description: >-
      Biallelic loss-of-function variants in any one of the four
      sarcoglycan genes (SGCA, SGCB, SGCG, SGCD) prevents normal folding,
      trafficking, or membrane insertion of that subunit, which secondarily
      destabilizes and reduces the other three sarcoglycans and the whole
      DGC at the sarcolemma.
    causal_link_type: DIRECT
- name: Sarcoglycan Complex Loss and DGC Destabilization
  biological_scale: CELLULAR
  description: >-
    Loss of one sarcoglycan subunit impairs assembly of the sarcoglycan
    subcomplex; the other three sarcoglycans, which depend on the missing
    subunit for stable membrane insertion, are secondarily reduced. Because
    the sarcoglycan-sarcospan subcomplex flanks and stabilizes dystroglycan
    within the DGC, its loss destabilizes the mechanical linkage of the
    whole complex between the muscle-fiber cytoskeleton and the basement
    membrane. Two lesion classes converge on this loss: null/frameshift
    variants (about a third of reported alleles) abolish the protein
    outright, while the more common missense variants (about two-thirds)
    typically produce a misfolded sarcoglycan that is recognized and
    prematurely degraded by the endoplasmic-reticulum-associated
    degradation (ERAD) quality-control pathway before it ever reaches the
    sarcolemma.
  cell_types:
  - preferred_term: skeletal muscle fiber
    term:
      id: CL:0008002
      label: skeletal muscle fiber
  protein_complexes:
  - preferred_term: dystrophin-associated glycoprotein complex
    term:
      id: GO:0016010
      label: dystrophin-associated glycoprotein complex
    modifier: DECREASED
  evidence:
  - reference: PMID:38713975
    reference_title: "Advanced therapeutic approaches in sarcoglycanopathies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The mutations impair the assembly of a key structural complex, which
      normally protects the sarcolemma of striated muscle from
      contraction-derived stress.
    explanation: >-
      States directly that sarcoglycan gene mutations impair assembly of the
      sarcoglycan/DGC structural complex, the shared upstream lesion across
      all four subtypes.
  - reference: PMID:36816759
    reference_title: "Systemic γ-sarcoglycan AAV gene transfer results in dose-dependent correction of muscle deficits in the LGMD 2C/R5 mouse model."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Loss of functional γ-sarcoglycan protein in the dystrophin-associated
      protein complex destabilizes the sarcolemma, leading to eventual
      myofiber death.
    explanation: >-
      A gamma-sarcoglycan-null mouse model directly demonstrates that loss
      of one sarcoglycan subunit destabilizes the DGC/sarcolemma.
  - reference: PMID:37628888
    reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      The δ-SG knockout line was further exploited to demonstrate that a
      δ-SG missense mutant is a substrate for
      endoplasmic-reticulum-associated degradation (ERAD), indicating premature degradation due
      to protein folding defects.
    explanation: >-
      A delta-sarcoglycan knockout zebrafish model directly demonstrates
      that a missense sarcoglycan variant is degraded by ERAD before
      reaching the membrane, the specific mechanism for the missense lesion
      class.
  - reference: PMID:37628888
    reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The genetic defects responsible for sarcoglycanopathy are, in most
      cases, missense mutations, accounting approximately for 67% of all
      cases, followed by frame shift and null mutations
    explanation: >-
      Directly supports the quantitative split between the missense (about
      two-thirds) and null/frameshift (about a third) lesion classes
      described in this node.
  downstream:
  - target: Contraction-Induced Sarcolemmal Membrane Damage
    description: >-
      A destabilized DGC can no longer transmit mechanical force across the
      sarcolemma, so the membrane can no longer withstand the stress of
      repeated muscle contraction.
    causal_link_type: DIRECT
- name: Contraction-Induced Sarcolemmal Membrane Damage
  biological_scale: CELLULAR
  description: >-
    The intact sarcoglycan-DGC complex normally undergoes chemical
    modification in response to contraction and mechanically stabilizes the
    sarcolemma against contraction-induced stress. With the complex
    destabilized, contraction produces microtears and, as in dystrophinopathy,
    a fragile and leaky sarcolemma; this alters intracellular calcium
    homeostasis and can eventually lead to mitochondrial dysfunction, driving
    cycles of myofiber injury.
  cell_types:
  - preferred_term: skeletal muscle fiber
    term:
      id: CL:0008002
      label: skeletal muscle fiber
  biological_processes:
  - preferred_term: calcium ion transport
    term:
      id: GO:0006816
      label: calcium ion transport
    modifier: ABNORMAL
  evidence:
  - reference: PMID:26709803
    reference_title: "The sarcoglycan complex in skeletal muscle."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      Once integrated, the sarcoglycan complex plays a pivotal role in
      mechanically stabilising the sarcolemma as well as the
      dystrophin-associated glycoprotein complex. Additionally, the
      sarcoglycan complex undergoes chemical modifications in response to
      muscle contractions, thereby transducing mechanical information into
      a cellular signal.
    explanation: >-
      Establishes the sarcoglycan complex's normal role in mechanically
      stabilizing the sarcolemma during contraction and transducing
      mechanical stress into a cellular signal, the process lost when the
      complex is destabilized.
  - reference: PMID:38713975
    reference_title: "Advanced therapeutic approaches in sarcoglycanopathies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The mutations impair the assembly of a key structural complex, which
      normally protects the sarcolemma of striated muscle from
      contraction-derived stress.
    explanation: >-
      Confirms that the sarcoglycan complex's normal function is to protect
      the sarcolemma from contraction-derived stress, and that this is what
      fails in sarcoglycanopathy.
  - reference: PMID:37628888
    reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: >-
      With the disruption of the SG-complex, it is thought that, like in
      DMD, the sarcolemma becomes fragile and leaky. This results in the
      subsequent alteration in the intracellular calcium homeostasis, which
      can eventually lead to mitochondrial dysfunction.
    explanation: >-
      Directly supports the calcium-ion-transport disturbance and downstream
      mitochondrial-dysfunction risk asserted on this node. Evidence source
      is OTHER because this is a discussion-section statement of the general
      sarcoglycanopathy mechanism (by analogy to DMD), not this paper's own
      zebrafish experimental data.
  downstream:
  - target: Progressive Myofiber Degeneration
    description: >-
      Repeated contraction-induced membrane injury that outpaces repair and
      regeneration leads to myofiber necrosis and chronic inflammation.
    causal_link_type: DIRECT
- name: Progressive Myofiber Degeneration
  biological_scale: CELLULAR
  description: >-
    Repeated contraction-induced membrane injury outpaces repair. Macrophages
    debride necrotic fibers and support satellite-cell-mediated regeneration,
    but when the degenerative process is massive or advanced, muscle stem
    cells can no longer sustain repair, so contractile tissue is
    progressively lost.
  cell_types:
  - preferred_term: skeletal muscle fiber
    term:
      id: CL:0008002
      label: skeletal muscle fiber
  - preferred_term: macrophage
    term:
      id: CL:0000235
      label: macrophage
  biological_processes:
  - preferred_term: muscle cell apoptotic process
    term:
      id: GO:0010657
      label: muscle cell apoptotic process
    modifier: INCREASED
  - preferred_term: inflammatory response
    term:
      id: GO:0006954
      label: inflammatory response
    modifier: INCREASED
  evidence:
  - reference: PMID:37628888
    reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      when the degenerative process is massive or at an advanced stage,
      muscle stem cells are unable to sustain the muscle repair, and the
      contractile muscle is progressively replaced by fibrotic or adipose
      tissue
    explanation: >-
      A delta-sarcoglycan knockout zebrafish model directly demonstrates
      that once regenerative capacity is exhausted, contractile tissue is
      progressively lost and replaced by fibrous and adipose tissue.
  downstream:
  - target: Fibrofatty Replacement of Skeletal Muscle
    description: >-
      Exhaustion of regenerative capacity leaves damaged contractile tissue
      progressively replaced by fibrous and adipose tissue.
    causal_link_type: DIRECT
- name: Fibrofatty Replacement of Skeletal Muscle
  biological_scale: TISSUE
  description: >-
    Contractile muscle tissue that outpaces regenerative capacity is
    progressively replaced by fibrous and adipose tissue, producing calf
    pseudohypertrophy early and irreversible weakness later.
  cell_types:
  - preferred_term: skeletal muscle fiber
    term:
      id: CL:0008002
      label: skeletal muscle fiber
  - preferred_term: fibroblast
    term:
      id: CL:0000057
      label: fibroblast
  evidence:
  - reference: PMID:37628888
    reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      These data suggest a severe skeletal muscle impairment, where damaged
      contractile tissue was partially replaced by fibrotic and adipose
      tissue, as demonstrated by the histological and TEM analyses of
      one-year-old zebrafish.
    explanation: >-
      Direct histological/ultrastructural demonstration of fibrofatty
      replacement of damaged contractile muscle in an adult sarcoglycan-null
      zebrafish model.
  - reference: PMID:39174842
    reference_title: "Molecular diagnosis of Alpha-sarcoglycanopathies by NGS in seven Moroccan families and report of two novel variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      It appears in childhood by progressive weakness of pelvic and/or
      scapular girdle muscles and calf hypertrophy, with a wide range of
      clinical inter- and intra-familial clinical variability.
    explanation: >-
      Documents calf hypertrophy and progressive proximal weakness, the
      clinical correlates of fibrofatty replacement, in alpha-sarcoglycanopathy.
  downstream:
  - target: Progressive proximal muscle weakness
    description: >-
      Loss of functional contractile muscle mass and its replacement by
      fibrofatty tissue manifests clinically as progressive proximal
      limb-girdle weakness.
    causal_link_type: DIRECT
  - target: Calf muscle hypertrophy
    description: >-
      Fibrofatty replacement and reactive enlargement of the calf
      musculature produce calf pseudohypertrophy, a characteristic early
      sign of sarcoglycanopathy.
    causal_link_type: DIRECT

phenotypes:
- name: Progressive proximal muscle weakness
  description: >-
    Symmetric, progressive weakness of the pelvic and shoulder girdle
    muscles, usually beginning in the first decade of life.
  phenotype_term:
    preferred_term: Limb-girdle muscle weakness
    term:
      id: HP:0003325
      label: Limb-girdle muscle weakness
    clinical_course: PROGRESSIVE
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:40757565
    reference_title: "An Update of Clinical, Epidemiological, and Psychosocial Features in Gamma-Sarcoglycanopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The most common symptoms are proximal limb-girdle muscle weakness or
      wasting (common in about 80-90% of cases)
    explanation: >-
      Quantifies proximal limb-girdle weakness as the most common feature
      of sarcoglycanopathy, occurring in 80-90% of cases.
- name: Elevated serum creatine kinase
  description: >-
    Serum creatine kinase is markedly elevated across all four
    sarcoglycanopathy subtypes.
  phenotype_term:
    preferred_term: Elevated circulating creatine kinase concentration
    term:
      id: HP:0003236
      label: Elevated circulating creatine kinase concentration
  evidence:
  - reference: PMID:34404573
    reference_title: "Sarcoglycanopathies: an update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients present muscle hypertrophy, elevated CK, variable muscle weaknesses, and progressive loss of ambulation."
    explanation: >-
      Documents elevated serum creatine kinase as a consistent finding
      across the sarcoglycanopathies.
  reports_on:
  - target: Sarcoglycan Complex Loss and DGC Destabilization
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: >-
      Ongoing myofiber membrane breakdown downstream of DGC destabilization
      releases intracellular creatine kinase into the circulation.
- name: Calf muscle hypertrophy
  description: >-
    Calf (pseudo)hypertrophy is a characteristic early sign across the
    sarcoglycanopathies, reflecting fibrofatty replacement and reactive
    enlargement of the calf musculature.
  phenotype_term:
    preferred_term: Calf muscle hypertrophy
    term:
      id: HP:0008981
      label: Calf muscle hypertrophy
  evidence:
  - reference: PMID:39174842
    reference_title: "Molecular diagnosis of Alpha-sarcoglycanopathies by NGS in seven Moroccan families and report of two novel variants."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      It appears in childhood by progressive weakness of pelvic and/or
      scapular girdle muscles and calf hypertrophy, with a wide range of
      clinical inter- and intra-familial clinical variability.
    explanation: >-
      Documents calf hypertrophy as a presenting sign of
      alpha-sarcoglycanopathy.
- name: Cardiomyopathy
  description: >-
    Dilated cardiomyopathy is an important complication of
    sarcoglycanopathy, especially in beta- and delta-sarcoglycanopathy; in
    gamma-sarcoglycanopathy it is reported in about 30% of cases.
  phenotype_term:
    preferred_term: Dilated cardiomyopathy
    term:
      id: HP:0001644
      label: Dilated cardiomyopathy
  frequency: FREQUENT
  evidence:
  - reference: PMID:33051934
    reference_title: "Clinical correlations and long-term follow-up in 100 patients with sarcoglycanopathies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Dilated cardiomyopathy occurred in all sarcoglycanopathy subtypes,
      especially in γ-SG patients (p = 0.01).
    explanation: >-
      A 100-patient multicenter cohort confirms cardiomyopathy occurs
      across all sarcoglycanopathy subtypes, most prominently in
      gamma-sarcoglycanopathy.
  - reference: PMID:12868499
    reference_title: "LGMD2E patients risk developing dilated cardiomyopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Given the age profile of the patients studied, the 50% cardiac
      involvement found in our LGMD2E patients is likely to be a
      conservative estimate.
    explanation: >-
      Quantifies cardiac involvement in a beta-sarcoglycanopathy (LGMDR4)
      patient cohort.
- name: Loss of ambulation
  description: >-
    Progressive weakness eventually results in loss of independent
    ambulation; in a 100-patient multicenter cohort, 65.3% of patients were
    wheelchair-bound at a mean follow-up of 22.9 years, and age at onset
    independently predicted time to loss of ambulation.
  phenotype_term:
    preferred_term: Loss of ambulation
    term:
      id: HP:0002505
      label: Loss of ambulation
  frequency: VERY_FREQUENT
  evidence:
  - reference: PMID:33051934
    reference_title: "Clinical correlations and long-term follow-up in 100 patients with sarcoglycanopathies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      At mean follow-up of 22.9 years, 65.3% of patients were
      wheelchair-bound (66.7% α-SG, 67.3% γ-SG, 40% β-SG).
    explanation: >-
      Quantifies the rate of loss of ambulation across sarcoglycanopathy
      subtypes at long-term follow-up.
  reports_on:
  - target: Fibrofatty Replacement of Skeletal Muscle
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: PROGNOSTIC
    interpretation: >-
      Loss of ambulation is the clinical endpoint of cumulative,
      irreversible fibrofatty replacement of contractile muscle.
- name: Cardiomyopathy in gamma-sarcoglycanopathy
  subtype: SGCG
  description: >-
    Dilated cardiomyopathy occurs in about 30% of gamma-sarcoglycanopathy
    (LGMDR5) cases.
  phenotype_term:
    preferred_term: Dilated cardiomyopathy
    term:
      id: HP:0001644
      label: Dilated cardiomyopathy
  frequency: FREQUENT
  evidence:
  - reference: PMID:40757565
    reference_title: "An Update of Clinical, Epidemiological, and Psychosocial Features in Gamma-Sarcoglycanopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      other frequent features are scoliosis (40%) cardiomyopathy (30%),
      respiratory deficiency (50-60%) and retractions (70%), which are
      frequently observed especially in advanced cases
    explanation: >-
      Quantifies cardiomyopathy frequency specifically in
      gamma-sarcoglycanopathy.
- name: Respiratory insufficiency due to muscle weakness
  subtype: SGCG
  description: >-
    Progressive respiratory muscle weakness produces restrictive
    respiratory insufficiency in about half to two-thirds of
    gamma-sarcoglycanopathy patients, particularly in advanced disease.
  phenotype_term:
    preferred_term: Respiratory insufficiency due to muscle weakness
    term:
      id: HP:0002747
      label: Respiratory insufficiency due to muscle weakness
    clinical_course: PROGRESSIVE
  frequency: FREQUENT
  evidence:
  - reference: PMID:40757565
    reference_title: "An Update of Clinical, Epidemiological, and Psychosocial Features in Gamma-Sarcoglycanopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      other frequent features are scoliosis (40%) cardiomyopathy (30%),
      respiratory deficiency (50-60%) and retractions (70%), which are
      frequently observed especially in advanced cases
    explanation: >-
      Quantifies respiratory deficiency frequency in gamma-sarcoglycanopathy.
- name: Scoliosis
  subtype: SGCG
  description: >-
    Axial and paraspinal muscle weakness leads to scoliosis in about 40% of
    gamma-sarcoglycanopathy patients.
  phenotype_term:
    preferred_term: Scoliosis
    term:
      id: HP:0002650
      label: Scoliosis
  frequency: FREQUENT
  evidence:
  - reference: PMID:40757565
    reference_title: "An Update of Clinical, Epidemiological, and Psychosocial Features in Gamma-Sarcoglycanopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      other frequent features are scoliosis (40%) cardiomyopathy (30%),
      respiratory deficiency (50-60%) and retractions (70%), which are
      frequently observed especially in advanced cases
    explanation: >-
      Quantifies scoliosis frequency in gamma-sarcoglycanopathy.
- name: Flexion contracture
  subtype: SGCG
  description: >-
    Joint contractures (retractions), including Achilles tendon shortening,
    develop in about 70% of gamma-sarcoglycanopathy patients as a
    consequence of chronic muscle weakness and imbalance.
  phenotype_term:
    preferred_term: Flexion contracture
    term:
      id: HP:0001371
      label: Flexion contracture
  frequency: FREQUENT
  evidence:
  - reference: PMID:40757565
    reference_title: "An Update of Clinical, Epidemiological, and Psychosocial Features in Gamma-Sarcoglycanopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      other frequent features are scoliosis (40%) cardiomyopathy (30%),
      respiratory deficiency (50-60%) and retractions (70%), which are
      frequently observed especially in advanced cases
    explanation: >-
      Quantifies retraction/contracture frequency in gamma-sarcoglycanopathy.
- name: Distal muscle weakness
  subtype: SGCD
  description: >-
    Distal muscle weakness of the limbs appears early in the disease course
    in a majority of delta-sarcoglycanopathy (LGMDR6) patients, in addition
    to the proximal weakness that is the more common presenting symptom
    across sarcoglycanopathy subtypes.
  phenotype_term:
    preferred_term: Distal muscle weakness
    term:
      id: HP:0002460
      label: Distal muscle weakness
  frequency: FREQUENT
  evidence:
  - reference: PMID:34515763
    reference_title: "Clinical and genetic spectrum of a large cohort of patients with δ-sarcoglycan muscular dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Distal muscle weakness was observed early over the course of the
      disease in 56.5% of the patients.
    explanation: >-
      The largest reported delta-sarcoglycanopathy cohort quantifies early
      distal muscle weakness in 56.5% of patients.
- name: Cardiac arrhythmia
  subtype: SGCD
  description: >-
    Heart rhythm abnormalities, distinct from dilated cardiomyopathy, occur
    in a subset of delta-sarcoglycanopathy (LGMDR6) patients with cardiac
    involvement.
  phenotype_term:
    preferred_term: Arrhythmia
    term:
      id: HP:0011675
      label: Arrhythmia
  evidence:
  - reference: PMID:34515763
    reference_title: "Clinical and genetic spectrum of a large cohort of patients with δ-sarcoglycan muscular dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Cardiac involvement, defined as cardiomyopathy or heart rhythm
      abnormalities, was reported in five patients (23.8%) with a median age
      of diagnosis of 13.0 years (range 11–17). Dilated cardiomyopathies
      were present in three patients (60%) and heart rhythm abnormalities
      were present in two patients.
    explanation: >-
      Documents heart rhythm abnormalities as a distinct component of
      cardiac involvement (alongside dilated cardiomyopathy) in a large
      delta-sarcoglycanopathy cohort.
- name: Respiratory insufficiency due to muscle weakness
  description: >-
    Progressive respiratory muscle weakness produces restrictive respiratory
    insufficiency requiring assisted or non-invasive ventilation in a
    substantial minority of patients across sarcoglycanopathy subtypes, not
    only in gamma-sarcoglycanopathy.
  phenotype_term:
    preferred_term: Respiratory insufficiency due to muscle weakness
    term:
      id: HP:0002747
      label: Respiratory insufficiency due to muscle weakness
    clinical_course: PROGRESSIVE
  evidence:
  - reference: PMID:25862795
    reference_title: "Clinical and genetic spectrum in limb-girdle muscular dystrophy type 2E."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Six patients had restrictive respiratory insufficiency requiring
      assisted ventilation (19%).
    explanation: >-
      Quantifies restrictive respiratory insufficiency requiring assisted
      ventilation in a 32-patient beta-sarcoglycanopathy (LGMDR4) cohort.
  - reference: PMID:34515763
    reference_title: "Clinical and genetic spectrum of a large cohort of patients with δ-sarcoglycan muscular dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Four patients (17.4%) required non-invasive ventilation.
    explanation: >-
      Quantifies non-invasive ventilation requirement in a large
      delta-sarcoglycanopathy (LGMDR6) cohort, confirming respiratory
      insufficiency is not confined to a single subtype.

prevalence:
- population: Worldwide
  measure_type: UNKNOWN
  prevalence_class: ULTRA_RARE
  notes: >-
    Figure is sarcoglycanopathies as a share of LGMD-R cases, not a
    population point-prevalence rate. No independently verifiable
    population point-prevalence figure was found for sarcoglycanopathy as a
    whole (a deep-research draft cited a beta-sarcoglycanopathy rate that
    could not be located in the cited paper's cached abstract and was
    therefore not used - see the PR description). Sarcoglycanopathies are
    consistently described as rare to ultra-rare, constituting an
    estimated 10-25% of LGMD-R cases overall, with
    delta-sarcoglycanopathy/LGMDR6 specifically the least frequent and most
    severe subtype.
  evidence:
  - reference: PMID:34404573
    reference_title: "Sarcoglycanopathies: an update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Sarcoglycanopathies are the most severe forms of autosomal recessive
      limb-girdle muscular dystrophies (LGMDs), constituting about 10-25%
      of LGMDs.
    explanation: >-
      Establishes sarcoglycanopathy's relative frequency among LGMD-R
      cases; a precise general-population prevalence figure was not
      independently verifiable.

histopathology:
- name: Necrosis and Regeneration (Dystrophic Changes)
  finding_term:
    preferred_term: Necrosis
    term:
      id: NCIT:C36184
      label: Necrosis
  description: >-
    Muscle biopsy shows the dystrophic pattern of fiber necrosis and
    regeneration characteristic of the limb-girdle muscular dystrophies,
    typically accompanied by elevated serum creatine kinase.
  diagnostic: true
  evidence:
  - reference: PMID:20301582
    reference_title: "Limb-Girdle Muscular Dystrophy Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The limb-girdle muscular dystrophies typically show
      degeneration/regeneration (dystrophic changes) on muscle biopsy,
      which is usually associated with elevated serum creatine kinase
      concentration.
    explanation: >-
      GeneReviews establishes the dystrophic degeneration/regeneration
      pattern on muscle biopsy as characteristic of the LGMDs, including
      sarcoglycanopathy.
- name: Endomysial Fibrosis with Inflammatory Infiltrate
  subtype: SGCD
  finding_term:
    preferred_term: Fibrosis
    term:
      id: NCIT:C3044
      label: Fibrosis
  description: >-
    Muscle biopsy in a large delta-sarcoglycanopathy (LGMDR6) cohort showed
    increased fibrotic tissue and necrotic fibers as the most frequent
    features, with inflammatory infiltrates in a minority of biopsies.
  frequency: FREQUENT
  evidence:
  - reference: PMID:34515763
    reference_title: "Clinical and genetic spectrum of a large cohort of patients with δ-sarcoglycan muscular dystrophy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Increase in the amount of fibrotic tissue and presence of necrotic
      muscle fibres were the most frequent features (64.3 and 50%,
      respectively). Inflammatory infiltrates were observed in 28.6% of
      biopsies
    explanation: >-
      Quantifies fibrosis, necrosis, and inflammatory infiltrate on muscle
      biopsy in a large delta-sarcoglycanopathy cohort.

diagnosis:
- name: Molecular genetic testing
  description: >-
    Diagnosis is established by identifying biallelic pathogenic variants in
    one of the four sarcoglycan genes, typically via a targeted
    neuromuscular NGS gene panel, supported by muscle biopsy
    immunohistochemistry showing loss or marked reduction of all four
    sarcoglycans (secondary to loss of the causal subunit).
  evidence:
  - reference: PMID:34404573
    reference_title: "Sarcoglycanopathies: an update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diagnosis is currently based on the molecular screening for these mutations."
    explanation: >-
      Confirms molecular genetic screening as the current diagnostic
      standard for sarcoglycanopathy.
  - reference: PMID:20301582
    reference_title: "Limb-Girdle Muscular Dystrophy Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Biochemical testing (i.e., protein testing by immunostaining or
      immunblotting) performed on a muscle biopsy can establish the
      diagnosis of the following LGMD types: sarcoglycanopathy,
      calpainopathy, dysferlinopathy, and O-linked glycosylation defects
      (also known as dystroglycanopathy).
    explanation: >-
      GeneReviews establishes muscle-biopsy immunostaining/immunoblotting as
      a route to establishing the sarcoglycanopathy diagnosis, complementing
      molecular genetic screening.
- name: Differential diagnosis - cognition is preserved
  description: >-
    Cognitive/intellectual impairment has never been reported in
    sarcoglycanopathy; new gait difficulty in a cognitively normal child is
    consistent with sarcoglycanopathy (or another muscular dystrophy) and
    should prompt CK testing and molecular workup rather than a primary
    neurodevelopmental diagnosis.
  evidence:
  - reference: PMID:37628888
    reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Cognitive impairment has never been reported."
    explanation: >-
      States directly that cognitive impairment is not a feature of
      sarcoglycanopathy.

clinical_trials:
- name: NCT06246513
  phase: PHASE_III
  status: ACTIVE_NOT_RECRUITING
  description: >-
    A Phase 3 multinational, open-label systemic gene-delivery study
    evaluating the safety and efficacy of a single systemic dose of
    SRP-9003 (bidridistrogene xeboparvovec), an AAVrh74 beta-sarcoglycan
    gene-transfer therapy, in ambulatory and non-ambulatory participants
    with beta-sarcoglycanopathy (LGMD2E/R4/SGCB).
  target_phenotypes:
  - preferred_term: Limb-girdle muscle weakness
    term:
      id: HP:0003325
      label: Limb-girdle muscle weakness
  evidence:
  - reference: clinicaltrials:NCT06246513
    reference_title: "A Phase 3 Multinational, Open-label, Systemic Gene Delivery Study to Evaluate the Safety and Efficacy of SRP-9003 in Subjects With Limb Girdle Muscular Dystrophy 2E/R4"
    supports: SUPPORT
    snippet: >-
      This is a multicenter, global study of the effects of a single
      systemic dose of SRP-9003 on beta-sarcoglycan (β-SG) gene expression
      in participants with limb-girdle muscular dystrophy, type 2E/R4
      (LGMD2E/R4).
    explanation: >-
      The trial summary confirms SRP-9003 is a systemic beta-sarcoglycan
      gene therapy in Phase 3 development for beta-sarcoglycanopathy.
- name: NCT03652259
  phase: PHASE_I
  status: TERMINATED
  description: >-
    The first-in-human, single-center, open-label systemic gene delivery
    study of SRP-9003 (bidridistrogene xeboparvovec) in participants with
    beta-sarcoglycanopathy (LGMD2E/R4); results reported at PMID:38177855
    are the direct clinical precursor to the Phase 3 trial (NCT06246513)
    above.
  notes: >-
    ClinicalTrials.gov lists phases PHASE1 and PHASE2; this schema stores
    PHASE_I as the nearest single early-phase value. Status is TERMINATED on
    ClinicalTrials.gov (checked 2026-08-26).
  target_phenotypes:
  - preferred_term: Limb-girdle muscle weakness
    term:
      id: HP:0003325
      label: Limb-girdle muscle weakness
  evidence:
  - reference: clinicaltrials:NCT03652259
    reference_title: "A Single-Center, Open-Label, Systemic Gene Delivery Study to Evaluate the Safety, Tolerability, and Efficacy of SRP-9003 Administered by Systemic Infusion in Subjects With LGMD2E (β-Sarcoglycan Deficiency)"
    supports: SUPPORT
    snippet: >-
      The proposed clinical trial is the first-in-human, single-center,
      open-label, gene delivery study of SRP-9003 (bidridistrogene
      xeboparvovec) in participants with LGMD2E.
    explanation: >-
      The trial summary confirms this is the first-in-human SRP-9003 study,
      the registration record for the PMID:38177855 Phase 1/2 results
      already cited under the AAV beta-sarcoglycan gene replacement
      treatment.
- name: NCT05876780
  phase: PHASE_I
  status: ACTIVE_NOT_RECRUITING
  description: >-
    A multicenter, open-label, single-dose systemic gene transfer study of
    SRP-9003 in both ambulatory and non-ambulatory participants with
    beta-sarcoglycanopathy (LGMD2E/R4), quantifying beta-sarcoglycan
    expression in skeletal muscle.
  target_phenotypes:
  - preferred_term: Limb-girdle muscle weakness
    term:
      id: HP:0003325
      label: Limb-girdle muscle weakness
  evidence:
  - reference: clinicaltrials:NCT05876780
    reference_title: "A Multicenter, Open-label, Single-dose, Systemic Gene Transfer Study to Evaluate the Safety, Tolerability, and Efficacy of SRP-9003 on Subjects With Limb Girdle Muscular Dystrophy, Type 2E/R4 (β-Sarcoglycan Deficiency)"
    supports: SUPPORT
    snippet: >-
      The primary purpose of this study is to evaluate the safety of
      SRP-9003 and to quantify expression of β-SG in the skeletal muscle of
      participants with limb-girdle muscular dystrophy, type 2E/R4
      (LGMD2E/R4).
    explanation: >-
      The trial summary confirms this Phase 1 study evaluates SRP-9003 in
      both ambulatory and non-ambulatory beta-sarcoglycanopathy patients.
- name: NCT05973630
  phase: PHASE_I
  status: ACTIVE_NOT_RECRUITING
  description: >-
    ATA-200, an AAV vector carrying the human SGCG gene, in a Phase 1
    open-label study of ambulant children with gamma-sarcoglycanopathy
    (LGMDR5) — the human trial that the AAV gamma-sarcoglycan gene transfer
    treatment (SRP-9005 mouse proof-of-concept) is cited against above.
  notes: >-
    ClinicalTrials.gov title lists phases PHASE1 and PHASE2; this schema
    stores PHASE_I as the nearest single early-phase value.
  target_phenotypes:
  - preferred_term: Limb-girdle muscle weakness
    term:
      id: HP:0003325
      label: Limb-girdle muscle weakness
  evidence:
  - reference: clinicaltrials:NCT05973630
    reference_title: "A Phase 1-2, Open-label Study to Evaluate the Safety of Intravenous ATA-200, an Adeno-associated Viral Vector Carrying the Human SGCG Gene, in Patients With Gamma-sarcoglycanopathy (LGMDR5)"
    supports: SUPPORT
    snippet: >-
      The purpose of ATA-003-GSAR study is to evaluate the safety and
      tolerability of a single intravenous infusion of ATA-200 in pediatric
      patients with limb girdle muscular dystrophy type 2c/R5 (LGMD R5).
    explanation: >-
      The trial summary confirms ATA-200 is an AAV-SGCG gene therapy in
      human Phase 1 development for gamma-sarcoglycanopathy.
- name: NCT04475926
  phase: NOT_APPLICABLE
  status: ACTIVE_NOT_RECRUITING
  description: >-
    Journey: a global, multicenter, longitudinal natural-history study
    following participants with beta- (LGMD2E/R4), alpha- (LGMD2D/R3), and
    gamma-sarcoglycanopathy (LGMD2C/R5), alongside calpainopathy
    (LGMD2A/R1), tracking mobility and pulmonary function for up to 5 years.
  target_phenotypes:
  - preferred_term: Limb-girdle muscle weakness
    term:
      id: HP:0003325
      label: Limb-girdle muscle weakness
  evidence:
  - reference: clinicaltrials:NCT04475926
    reference_title: "Journey: A Global, Multicenter, Longitudinal Study of the Natural History of Subjects With Limb Girdle Muscular Dystrophy (LGMD) Type 2E (LGMD2E/R4), Type 2D (LGMD2D/R3), Type 2C (LGMD2C/R5), and Type 2A (LGMD2A/R1)"
    supports: SUPPORT
    snippet: >-
      This study will follow participants who are screened and confirmed
      with a genetic diagnosis of Limb-girdle muscular dystrophy type 2E
      (LGMD2E/R4), Limb-girdle muscular dystrophy type 2D (LGMD2D/R3),
      Limb-girdle muscular dystrophy type 2C (LGMD2C/R5), or Limb-girdle
      muscular dystrophy type 2A (LGMD2A/R1).
    explanation: >-
      Confirms this observational natural-history study enrolls three of
      the four sarcoglycanopathy subtypes (alongside the genetically
      distinct calpainopathy) to characterize disease progression.

treatments:
- name: Supportive care (physical therapy and rehabilitation)
  description: >-
    No curative or disease-modifying therapy is currently approved for any
    sarcoglycanopathy subtype; management is supportive, centered on
    physical therapy, stretching, and mobility aids to preserve function
    and prevent contractures.
  therapeutic_modality: BEHAVIORAL
  treatment_term:
    preferred_term: physical therapy
    term:
      id: NCIT:C15302
      label: Physical Therapy
  evidence:
  - reference: PMID:38713975
    reference_title: "Advanced therapeutic approaches in sarcoglycanopathies."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "There is currently no effective treatment available; however, both gene replacement strategy and small molecule-based approaches show great promise and have entered or are starting to enter clinical trials."
    explanation: >-
      Confirms that no curative treatment currently exists for
      sarcoglycanopathy, underscoring the role of supportive management
      while disease-modifying approaches remain investigational.
  - reference: PMID:20301582
    reference_title: "Limb-Girdle Muscular Dystrophy Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      physical therapy and stretching exercises to promote mobility and
      prevent contractures
    explanation: >-
      GeneReviews recommends physical therapy and stretching exercises as
      standard supportive management for limb-girdle muscular dystrophy,
      including sarcoglycanopathy.
- name: Cardiorespiratory surveillance
  description: >-
    Regular cardiac (echocardiography/ECG) and pulmonary function
    monitoring are indicated given the substantial risk of dilated
    cardiomyopathy and restrictive respiratory insufficiency, particularly
    in beta-, gamma-, and delta-sarcoglycanopathy.
  therapeutic_modality: OTHER
  treatment_term:
    preferred_term: cardiac and respiratory surveillance
    term:
      id: NCIT:C15747
      label: Supportive Care
  evidence:
  - reference: PMID:12868499
    reference_title: "LGMD2E patients risk developing dilated cardiomyopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Careful cardiac monitoring should be carried out in beta-sarcoglycanopathy patients who are at high risk of developing cardiomyopathy."
    explanation: >-
      Directly recommends cardiac monitoring in beta-sarcoglycanopathy
      patients given their high risk of cardiomyopathy.
  - reference: PMID:20301582
    reference_title: "Limb-Girdle Muscular Dystrophy Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "monitoring for cardiomyopathy in LGMD types with cardiac involvement"
    explanation: >-
      GeneReviews lists monitoring for cardiomyopathy as standard management
      for LGMD types with cardiac involvement, including sarcoglycanopathy.
- name: Guideline-directed heart failure pharmacotherapy for beta-sarcoglycanopathy cardiomyopathy
  description: >-
    Standard heart-failure pharmacotherapy (ACE inhibitors and
    beta-adrenergic antagonists) is used to manage the
    sarcoglycanopathy-associated dilated cardiomyopathy once it develops, particularly in
    beta-sarcoglycanopathy (SGCB/LGMDR4) where cardiac involvement is
    common.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: ACE inhibitor
      term:
        id: NCIT:C247
        label: ACE Inhibitor
    - preferred_term: beta-blocker
      term:
        id: NCIT:C29576
        label: Beta-Adrenergic Antagonist
  evidence:
  - reference: PMID:12868499
    reference_title: "LGMD2E patients risk developing dilated cardiomyopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Careful cardiac monitoring should be carried out in beta-sarcoglycanopathy patients who are at high risk of developing cardiomyopathy."
    explanation: >-
      Establishes the high risk of cardiomyopathy in beta-sarcoglycanopathy
      that underpins the standard heart-failure pharmacotherapy indication.
- name: AAV beta-sarcoglycan gene replacement therapy (SGCB)
  description: >-
    Bidridistrogene xeboparvovec (SRP-9003), an AAVrh74 vector delivering a
    codon-optimized SGCB transgene, produced robust dose-dependent
    beta-sarcoglycan expression (mean 36.2% and 62.1% of normal at Day 60
    in low- and high-dose cohorts, respectively) and preliminary motor
    improvements maintained through 2 years in a 6-patient Phase 1/2
    first-in-human trial, and has since progressed to a Phase 3
    multinational trial (NCT06246513) for beta-sarcoglycanopathy.
  treatment_term:
    preferred_term: gene therapy
    term:
      id: NCIT:C15238
      label: Gene Therapy
  therapeutic_modality: GENE_THERAPY
  evidence:
  - reference: PMID:38177855
    reference_title: "Gene therapy with bidridistrogene xeboparvovec for limb-girdle muscular dystrophy type 2E/R4: phase 1/2 trial results."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Robust SGCB expression was observed: Day 60 mean (s.d.) percentage of
      normal expression 36.2% (2.7%) in Cohort 1 and 62.1% (8.7%) in Cohort
      2. Post hoc exploratory analysis showed preliminary motor
      improvements using the North Star Assessment for Limb-girdle Type
      Muscular Dystrophies maintained through Year 2.
    explanation: >-
      Reports the interim Phase 1/2 first-in-human results for AAV
      beta-sarcoglycan gene replacement therapy, the direct clinical
      precursor to the Phase 3 trial cited above.
  - reference: PMID:34404573
    reference_title: "Sarcoglycanopathies: an update."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      Therapeutic approaches include the strategy of gene replacement
      mediated by a vector derived from adeno-associated virus (AAV).
      Pre-clinical studies have shown detectable levels of SG proteins in
      the muscle, and some improvement in the phenotype, in animal models.
      Therapeutic trials in humans are ongoing.
    explanation: >-
      Confirms AAV-mediated sarcoglycan gene replacement as an active
      therapeutic strategy across the sarcoglycanopathies generally.
  target_mechanisms:
  - target: Sarcoglycan Complex Loss and DGC Destabilization
    treatment_effect: RESTORES
    description: >-
      AAVrh74-mediated SGCB gene transfer restores beta-sarcoglycan
      expression, directly addressing the missing subunit that destabilizes
      the sarcoglycan subcomplex and the DGC.
    evidence:
    - reference: PMID:38177855
      reference_title: "Gene therapy with bidridistrogene xeboparvovec for limb-girdle muscular dystrophy type 2E/R4: phase 1/2 trial results."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        Robust SGCB expression was observed: Day 60 mean (s.d.) percentage
        of normal expression 36.2% (2.7%) in Cohort 1 and 62.1% (8.7%) in
        Cohort 2.
      explanation: >-
        Directly demonstrates restoration of beta-sarcoglycan expression in
        human patients following AAV gene transfer.
- name: Investigational small-molecule ERAD inhibition
  description: >-
    Misfolded missense sarcoglycan variants are degraded by the
    ER-associated degradation (ERAD) quality-control pathway before reaching
    the sarcolemma; pharmacologically inhibiting this proteolysis is
    proposed as a mutation-class-specific small-molecule therapeutic
    strategy to increase the amount of (partially functional) sarcoglycan
    that reaches the membrane.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
  therapeutic_modality: SMALL_MOLECULE
  evidence:
  - reference: PMID:40757565
    reference_title: "An Update of Clinical, Epidemiological, and Psychosocial Features in Gamma-Sarcoglycanopathy."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The residual altered proteins are destroyed by a proteolytic
      quality-control system or endoplasmic reticulum-associated
      degradation, ERAD. The inhibition of this proteolysis makes these
      proteins more available to migrate to the sarcolemma and thus
      becomes a potential therapeutic objective
    explanation: >-
      States the ERAD-inhibition therapeutic rationale directly, applicable
      to missense sarcoglycan variants across subtypes.
  target_mechanisms:
  - target: Sarcoglycan Complex Loss and DGC Destabilization
    treatment_effect: INHIBITS
    description: >-
      Inhibiting ERAD-mediated proteolysis of misfolded missense sarcoglycan
      is intended to make more of the (partially functional) protein
      available to reach the sarcolemma, partially counteracting complex
      loss for the missense lesion class.
    evidence:
    - reference: PMID:40757565
      reference_title: "An Update of Clinical, Epidemiological, and Psychosocial Features in Gamma-Sarcoglycanopathy."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: >-
        The inhibition of this proteolysis makes these proteins more
        available to migrate to the sarcolemma and thus becomes a potential
        therapeutic objective
      explanation: >-
        States the ERAD-inhibition mechanism-of-action directly, linking the
        treatment to the sarcoglycan-complex-loss node it targets.
- name: Investigational AAV gamma-sarcoglycan gene transfer (SGCG)
  description: >-
    A self-complementary AAVrh74 vector (SRP-9005) carrying a
    codon-optimized human SGCG transgene restored sarcoglycan complex
    expression, muscle histopathology, and functional performance in a
    Sgcg-null mouse model, supporting translation to human
    gamma-sarcoglycanopathy. An AAV vector carrying human SGCG (ATA-200) has
    since entered a Phase 1 human trial (NCT05973630) in ambulant children
    with gamma-sarcoglycanopathy (LGMDR5).
  treatment_term:
    preferred_term: gene therapy
    term:
      id: NCIT:C15238
      label: Gene Therapy
  therapeutic_modality: GENE_THERAPY
  evidence:
  - reference: PMID:36816759
    reference_title: "Systemic γ-sarcoglycan AAV gene transfer results in dose-dependent correction of muscle deficits in the LGMD 2C/R5 mouse model."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      This study demonstrates successful systemic delivery of the hSGCG
      transgene in SGCG -/- mice, with functional protein expression,
      reconstitution of the sarcoglycan complex, and corresponding
      physiological and functional improvements, which will help establish
      a minimal effective dose for translation of SRP-9005 gene transfer
      therapy in patients with LGMD 2C/R5.
    explanation: >-
      Preclinical mouse study establishing proof of principle for AAV
      gamma-sarcoglycan gene transfer, aimed at future clinical translation.
  - reference: clinicaltrials:NCT05973630
    reference_title: "A Phase 1-2, Open-label Study to Evaluate the Safety of Intravenous ATA-200, an Adeno-associated Viral Vector Carrying the Human SGCG Gene, in Patients With Gamma-sarcoglycanopathy (LGMDR5)"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      The purpose of ATA-003-GSAR study is to evaluate the safety and
      tolerability of a single intravenous infusion of ATA-200 in pediatric
      patients with limb girdle muscular dystrophy type 2c/R5 (LGMD R5).
    explanation: >-
      Confirms an AAV-SGCG gene therapy (ATA-200) has entered human clinical
      trial, the translation from the mouse proof-of-concept study above.
  target_mechanisms:
  - target: Sarcoglycan Complex Loss and DGC Destabilization
    treatment_effect: RESTORES
    description: >-
      AAV-mediated SGCG gene transfer restores gamma-sarcoglycan expression
      and reconstitutes the sarcoglycan complex.
    evidence:
    - reference: PMID:36816759
      reference_title: "Systemic γ-sarcoglycan AAV gene transfer results in dose-dependent correction of muscle deficits in the LGMD 2C/R5 mouse model."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        This study demonstrates successful systemic delivery of the hSGCG
        transgene in SGCG -/- mice, with functional protein expression,
        reconstitution of the sarcoglycan complex, and corresponding
        physiological and functional improvements, which will help
        establish a minimal effective dose for translation of SRP-9005 gene
        transfer therapy in patients with LGMD 2C/R5.
      explanation: >-
        Directly demonstrates reconstitution of the sarcoglycan complex
        following AAV-SGCG gene transfer in a mouse model.
- name: Genetic counseling
  description: >-
    Genetic counseling is essential for carrier identification,
    recurrence-risk assessment, and reproductive planning once the causal
    sarcoglycan gene has been identified by molecular testing.
  treatment_term:
    preferred_term: genetic counseling
    term:
      id: NCIT:C15240
      label: Genetic Counseling
  evidence:
  - reference: PMID:20301582
    reference_title: "Limb-Girdle Muscular Dystrophy Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: >-
      If the causative pathogenic variant(s) have been identified in the
      family, prenatal testing for pregnancies at increased risk is
      possible.
    explanation: >-
      GeneReviews directly states the reproductive-planning/prenatal-testing
      rationale for genetic counseling once the causal variant is known,
      replacing an earlier snippet that only supported the diagnostic
      prerequisite rather than counseling itself.

animal_models:
- name: Sgcb-, Sgcg-, or Sgcd-null mouse (individual knockout)
  species: Mouse
  genotype: Individual germline knockout of Sgcb, Sgcg, or Sgcd
  publication: PMID:37628888
  description: >-
    Individual knockout of any one of Sgcb, Sgcg, or Sgcd in mice produces
    progressive skeletal-muscle dystrophy and, unlike the Sgca-null mouse
    below, dilated or hypertrophic cardiomyopathy — mirroring the
    beta-, gamma-, and delta-sarcoglycanopathy pattern of substantial human
    cardiac involvement.
  evidence:
  - reference: PMID:37628888
    reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      All these KO animals present signs of progressive dystrophy in
      skeletal musculature, whereas dilated or hypertrophic cardiomyopathy
      develops in β- γ-, and δ-SG-, but not in α-SG-null mice
    explanation: >-
      Summary statement (citing the primary mouse-model literature) of the
      shared skeletal phenotype and beta/gamma/delta-specific cardiac
      phenotype across the individual sarcoglycan-null mouse lines.
  modeled_mechanisms:
  - target: Sarcoglycan Complex Loss and DGC Destabilization
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Germline loss of the corresponding sarcoglycan subunit destabilizes
      the DGC, as in human disease.
    evidence:
    - reference: PMID:37628888
      reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        All these KO animals present signs of progressive dystrophy in
        skeletal musculature, whereas dilated or hypertrophic cardiomyopathy
        develops in β- γ-, and δ-SG-, but not in α-SG-null mice
      explanation: >-
        Establishes that loss of the corresponding sarcoglycan subunit
        produces progressive dystrophy across these mouse lines.
  - target: Progressive Myofiber Degeneration
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Each knockout line develops progressive dystrophic changes in skeletal
      muscle.
    evidence:
    - reference: PMID:37628888
      reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        All these KO animals present signs of progressive dystrophy in
        skeletal musculature, whereas dilated or hypertrophic cardiomyopathy
        develops in β- γ-, and δ-SG-, but not in α-SG-null mice
      explanation: >-
        States directly that all sarcoglycan-null mouse lines present
        progressive dystrophy in skeletal musculature.
  - target: Cardiomyopathy
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Beta-, gamma-, and delta-sarcoglycan-null mice develop dilated or
      hypertrophic cardiomyopathy, paralleling the cardiac involvement
      documented in the corresponding human subtypes.
    evidence:
    - reference: PMID:37628888
      reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        All these KO animals present signs of progressive dystrophy in
        skeletal musculature, whereas dilated or hypertrophic cardiomyopathy
        develops in β- γ-, and δ-SG-, but not in α-SG-null mice
      explanation: >-
        Directly states that beta-, gamma-, and delta-sarcoglycan-null mice
        develop cardiomyopathy.
- name: Sgca-null mouse (knockout)
  species: Mouse
  genotype: Sgca germline knockout
  publication: PMID:37628888
  description: >-
    Alpha-sarcoglycan-null mice develop progressive skeletal-muscle
    dystrophy but generally do not develop the cardiomyopathy seen in the
    other three sarcoglycan-null mouse lines, despite substantial cardiac
    involvement being documented in human alpha-sarcoglycanopathy (LGMDR3)
    patients.
  evidence:
  - reference: PMID:37628888
    reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      All these KO animals present signs of progressive dystrophy in
      skeletal musculature, whereas dilated or hypertrophic cardiomyopathy
      develops in β- γ-, and δ-SG-, but not in α-SG-null mice
    explanation: >-
      Directly states that alpha-sarcoglycan-null mice, unlike the other
      three sarcoglycan-null lines, generally do not develop cardiomyopathy.
  modeled_mechanisms:
  - target: Sarcoglycan Complex Loss and DGC Destabilization
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Sgca-null mice recapitulate loss-driven progressive skeletal-muscle
      dystrophy.
    evidence:
    - reference: PMID:37628888
      reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        All these KO animals present signs of progressive dystrophy in
        skeletal musculature, whereas dilated or hypertrophic cardiomyopathy
        develops in β- γ-, and δ-SG-, but not in α-SG-null mice
      explanation: >-
        States that all sarcoglycan-null mouse lines, including Sgca-null,
        present progressive skeletal-muscle dystrophy.
  - target: Cardiomyopathy
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    description: >-
      Unlike Sgcb-, Sgcg-, and Sgcd-null mice, Sgca-null mice generally do
      not develop cardiomyopathy.
    limitations: >-
      Human alpha-sarcoglycanopathy (LGMDR3) patients document cardiac
      involvement (e.g., dilated cardiomyopathy across sarcoglycanopathy
      subtypes generally), but the Sgca-null mouse does not reproduce a
      cardiac phenotype, limiting its usefulness for studying
      alpha-sarcoglycan-specific cardiac disease mechanisms or testing
      cardioprotective interventions.
    evidence:
    - reference: PMID:37628888
      reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        All these KO animals present signs of progressive dystrophy in
        skeletal musculature, whereas dilated or hypertrophic cardiomyopathy
        develops in β- γ-, and δ-SG-, but not in α-SG-null mice
      explanation: >-
        Directly states that alpha-sarcoglycan-null mice, unlike the other
        three lines, generally do not develop cardiomyopathy — a genuine
        negative result for cardiac-mechanism modeling.
- name: Missense sarcoglycan knock-in (KI) mouse
  species: Mouse
  genotype: Missense sarcoglycan knock-in (three independent lines generated to date)
  publication: PMID:37628888
  description: >-
    Because missense mutations account for the majority (about two-thirds)
    of reported sarcoglycanopathy alleles, knock-in (KI) mice carrying a
    missense sarcoglycan variant would in principle be the more
    disease-relevant model class relative to null/knockout lines. However,
    the three sarcoglycan missense knock-in mouse lines generated to date
    have failed to develop a myopathic phenotype at all.
  evidence:
  - reference: PMID:37628888
    reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      we must consider that the three SG-KI mice, generated until now,
      failed to develop a myopathic phenotype
    explanation: >-
      States directly that all three missense sarcoglycan knock-in mouse
      lines generated to date fail to develop any myopathic phenotype.
  modeled_mechanisms:
  - target: Sarcoglycan Complex Loss and DGC Destabilization
    relationship: FAILS_TO_RECAPITULATE
    fidelity: LOW
    description: >-
      Missense knock-in mice fail to develop any myopathic phenotype,
      despite missense variants being the most common human
      sarcoglycanopathy lesion class and the ERAD-mediated-degradation
      mechanism being demonstrated directly in a zebrafish missense model
      (see the sgcb/sgcd-null zebrafish model below).
    limitations: >-
      All three sarcoglycan missense knock-in mouse lines generated to date
      fail to develop a myopathic phenotype, unlike the null/knockout mouse
      lines — limiting mouse KI models' usefulness for studying the
      missense/ERAD lesion class that predominates in human patients, and
      motivating the zebrafish missense-modeling approach instead.
    evidence:
    - reference: PMID:37628888
      reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        we must consider that the three SG-KI mice, generated until now,
        failed to develop a myopathic phenotype
      explanation: >-
        Directly documents the negative result: existing missense
        knock-in mouse models do not reproduce a myopathic phenotype.
- name: δ-sarcoglycan-deficient Syrian hamster (naturally occurring)
  species: Syrian hamster (Mesocricetus auratus)
  genotype: Naturally occurring delta-sarcoglycan deficiency
  publication: PMID:37628888
  description: >-
    Naturally occurring delta-sarcoglycan-deficient hamster strains develop
    both skeletal myopathy and cardiomyopathy resembling human
    delta-sarcoglycanopathy (LGMDR6), and are considered one of the two
    animal-model classes (with sarcoglycan-knockout mice) that best mimic
    human sarcoglycanopathy.
  evidence:
  - reference: PMID:37628888
    reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: >-
      Currently, the animal models that best mimic sarcoglycanopathies are
      SG-KO mice and the naturally occurring δ-SG mutants identified in
      several hamster strains. They develop muscle and heart problems, as
      in humans
    explanation: >-
      States directly that naturally occurring delta-sarcoglycan-deficient
      hamster strains develop both muscle and heart problems mirroring
      human disease.
  modeled_mechanisms:
  - target: Sarcoglycan Complex Loss and DGC Destabilization
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      A naturally occurring loss-of-function delta-sarcoglycan deficiency,
      closely paralleling the human LGMDR6 genetic mechanism.
    evidence:
    - reference: PMID:37628888
      reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        Currently, the animal models that best mimic sarcoglycanopathies
        are SG-KO mice and the naturally occurring δ-SG mutants identified
        in several hamster strains. They develop muscle and heart problems,
        as in humans
      explanation: >-
        Identifies the naturally occurring hamster delta-sarcoglycan
        deficiency as one of the two best-mimicking animal-model classes.
  - target: Cardiomyopathy
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      Hamster models of delta-sarcoglycan deficiency develop both
      hypertrophic and dilated cardiomyopathy, mirroring the cardiac
      involvement documented in human delta-sarcoglycanopathy.
    evidence:
    - reference: PMID:37628888
      reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        In the hamster models of δ-sarcoglycanopathy, both hypertrophic and
        dilated cardiomyopathies have been described
      explanation: >-
        States directly that hamster models of delta-sarcoglycan deficiency
        develop both hypertrophic and dilated cardiomyopathy.
- name: sgcb-/- and sgcd-/- zebrafish (CRISPR knockout)
  species: Zebrafish
  genotype: >-
    CRISPR/Cas9-induced exon 2 frameshift null alleles of sgcb and sgcd
    (independent lines); the sgcd-/- line was characterized in most detail
  publication: PMID:37628888
  description: >-
    CRISPR/Cas9 knockout zebrafish lines for sgcb and sgcd show a mild
    larval phenotype that progresses to adult dystrophic skeletal muscle and
    cardiomyopathy, and the sgcd-/- line was used to directly demonstrate
    ERAD-mediated degradation of a missense delta-sarcoglycan variant.
  evidence:
  - reference: PMID:37628888
    reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
    supports: SUPPORT
    evidence_source: MODEL_ORGANISM
    snippet: "we observed clear signs of dystrophy and cardiomyopathy, well-resembling the human condition"
    explanation: >-
      Direct primary-data statement that adult sarcoglycan-null zebrafish
      recapitulate both the dystrophic and cardiac features of human
      sarcoglycanopathy.
  modeled_mechanisms:
  - target: Sarcoglycan Complex Loss and DGC Destabilization
    relationship: RECAPITULATES
    fidelity: HIGH
    description: >-
      The sgcd-/- knockout line was used to directly demonstrate that a
      missense delta-sarcoglycan variant is a substrate for ERAD, the
      specific molecular mechanism proposed for the missense lesion class in
      human sarcoglycanopathy.
    evidence:
    - reference: PMID:37628888
      reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        The δ-SG knockout line was further exploited to demonstrate that a
        δ-SG missense mutant is a substrate for
        endoplasmic-reticulum-associated degradation (ERAD), indicating
        premature degradation due to protein folding defects.
      explanation: >-
        Direct experimental demonstration of ERAD-mediated degradation of a
        missense sarcoglycan variant in this zebrafish model.
  - target: Progressive Myofiber Degeneration
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Adult sgcd-/- zebrafish develop severe skeletal-muscle impairment with
      contractile tissue partially replaced by fibrotic and adipose tissue,
      following an initially mild larval phenotype.
    limitations: >-
      The overt dystrophic phenotype emerges only in adulthood; larval-stage
      zebrafish show minimal muscle damage despite complete loss of
      sarcoglycan protein, so early-life screening in this model would
      under-detect the phenotype.
    evidence:
    - reference: PMID:37628888
      reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        These data suggest a severe skeletal muscle impairment, where
        damaged contractile tissue was partially replaced by fibrotic and
        adipose tissue, as demonstrated by the histological and TEM
        analyses of one-year-old zebrafish.
      explanation: >-
        Direct histological/ultrastructural demonstration of progressive
        myofiber degeneration and fibrofatty replacement in adult sgcd-/-
        zebrafish.
  - target: Cardiomyopathy
    relationship: RECAPITULATES
    fidelity: MODERATE
    description: >-
      Adult sgcd-/- zebrafish develop cardiomyopathy, evident both
      macroscopically and microscopically, although no cardiac abnormality
      is present at larval stages.
    limitations: >-
      No cardiac phenotype is detectable during early larval development,
      so this model would yield a false negative for cardiac involvement if
      assessed too early; the paper also notes further studies are needed
      to characterize the type and onset of cardiomyocyte damage relative
      to mammalian sarcoglycanopathy.
    evidence:
    - reference: PMID:37628888
      reference_title: "Modeling Sarcoglycanopathy in Danio rerio."
      supports: SUPPORT
      evidence_source: MODEL_ORGANISM
      snippet: >-
        the absence of δ-SG from the DAPC in the cardiomyocyte membrane
        produced signs of cardiomyopathy, evident both macroscopically and
        microscopically in adulthood
      explanation: >-
        Direct demonstration that adult sgcd-/- zebrafish develop
        cardiomyopathy secondary to loss of delta-sarcoglycan from the
        cardiomyocyte membrane.

discussions:
- discussion_id: sgcd-recessive-vs-dominant-cardiomyopathy
  prompt: >-
    Should evidence for dominant-negative SGCD missense variants causing
    isolated familial dilated cardiomyopathy be used to support the
    pathophysiology of recessive LGMDR6 (delta-sarcoglycanopathy)?
  kind: INTERPRETATION
  status: RESOLVED
  attaches_to:
  - "has_subtypes#SGCD"
  rationale: >-
    Delta-sarcoglycan is essential for both skeletal and cardiac
    dystrophin-glycoprotein complex stability, but two distinct SGCD
    mutation classes produce clinically distinct diseases: biallelic
    loss-of-function variants cause recessive LGMDR6 (this entry, with
    skeletal myopathy plus variable cardiac involvement), while rare
    heterozygous dominant-negative missense variants (e.g., R71T, R97Q)
    cause isolated familial dilated cardiomyopathy without skeletal
    myopathy, by destabilizing cardiac myocyte membrane mechanics without
    perturbing overall DGC assembly. This entry cites the dominant-negative
    mechanism only as background evidence for delta-sarcoglycan's general
    importance to cardiac membrane stability, and does not use it as direct
    evidence for the recessive LGMDR6 cardiac phenotype.
  evidence:
  - reference: PMID:26968544
    reference_title: "Dilated cardiomyopathy mutations in δ-sarcoglycan exert a dominant-negative effect on cardiac myocyte mechanical stability."
    supports: SUPPORT
    evidence_source: IN_VITRO
    snippet: >-
      While recessive mutations in δ-sarcoglycan cause limb girdle muscular
      dystrophy 2F, dominant mutations in δ-sarcoglycan have been linked to
      inherited dilated cardiomyopathy (DCM).
    explanation: >-
      The paper itself distinguishes the recessive LGMD2F (LGMDR6) allele
      class curated in this entry from the separate dominant DCM-causing
      allele class it studies, supporting the scoping decision above.
  resolution_note: >-
    Scoped SGCD subtype description and evidence to the recessive
    loss-of-function mechanism only; the dominant DCM mechanism is
    documented here for context but is out of scope for this entry.

datasets: []

📚

References & Deep Research

References

1

PMID:20301582

Limb-Girdle Muscular Dystrophy Overview – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY.

No top-level findings curated for this source.

Deep Research

1

Falcon ▸

Disease Characteristics Research Template

Edison Scientific Literature 21 citations 2026-08-26T16:43:19.954358

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on: 1. Key concepts and definitions with current understanding 2. Recent developments and latest research (prioritize 2023-2024 sources) 3. Current applications and real-world implementations 4. Expert opinions and analysis from authoritative sources 5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available. Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Disease Characteristics Research Template

Target Disease

Disease Name: Sarcoglycanopathy
MONDO ID: (if available)
Category: Mendelian

Research Objectives

Please provide a comprehensive research report on Sarcoglycanopathy covering all of the disease characteristics listed below. This report will be used to populate a disease knowledge base entry. Be thorough and cite primary literature (PMID preferred) for all claims.

For each section, suggested databases/resources are listed. These are the first places you should search for information on each topic.

1. Disease Information

Search first: OMIM, Orphanet, ICD-10/ICD-11, MeSH, PubMed

What is the disease? Provide a concise overview.
What are the key identifiers? (OMIM, Orphanet, ICD-10/ICD-11, MeSH, Mondo)
What are the common synonyms and alternative names?
Is the information derived from individual patients (e.g., EHR) or aggregated disease-level resources?

2. Etiology

Disease Causal Factors: What are the primary causes? (genetic, environmental, infectious, mechanistic)
Risk Factors:

Search first: PubMed, Cochrane Library, UpToDate, clinical guidelines, ClinVar, ClinGen, GWAS Catalog, PheGenI, CTD, CDC, WHO, epidemiological databases
Genetic risk factors (causal variants, susceptibility loci, modifier genes)
Environmental risk factors (toxins, lifestyle, occupational exposures, age, sex, family history)
Protective Factors:

Search first: PubMed, Cochrane Library, clinical trial databases, GWAS Catalog, gnomAD, WHO, CDC, nutrition databases
Genetic protective factors (protective variants, modifier alleles)
Environmental protective factors (diet, lifestyle, exposures that reduce risk)
Gene-Environment Interactions: How do genetic and environmental factors interact to influence disease?

Search first: CTD, PubMed, PheGenI, GxE databases

3. Phenotypes

Search first: HPO (Human Phenotype Ontology), OMIM, Orphanet, PubMed, clinicaltrials.gov, MedDRA, SNOMED CT, DECIPHER, LOINC

For each phenotype, provide: - Phenotype type: symptoms, clinical signs, physical manifestations, behavioral changes, or laboratory abnormalities

For symptoms/signs: HPO, OMIM, Orphanet, PubMed For behavioral changes: HPO, DSM, RDoC (Research Domain Criteria), PubMed For laboratory abnormalities: LOINC, SNOMED CT, LabTests Online, PubMed - Phenotype characteristics: Search first: OMIM, Orphanet, HPO, PubMed - Age of symptom onset (neonatal, childhood, adult-onset, late-onset) - Symptom severity (mild, moderate, severe, variable) - Symptom progression (stable, progressive, episodic, fluctuating) - Frequency among affected individuals (percentage or qualitative) - Quality of life impact: Effects on daily functioning and well-being (per-phenotype when possible) Search first: EQ-5D database, SF-36, WHO QOL databases, PubMed - Suggest HPO (Human Phenotype Ontology) terms for each phenotype

4. Genetic/Molecular Information

Causal Genes: Gene mutations or chromosomal abnormalities responsible for disease (gene symbols, OMIM IDs)

Search first: OMIM, ClinVar, HGMD, Ensembl, NCBI Gene
Pathogenic Variants:
Affected genes (gene symbols, HGNC IDs) > Search first: OMIM, NCBI Gene, Ensembl, HGNC, UniProt, GeneCards
Variant classification (pathogenic, likely pathogenic, VUS per ACMG/AMP guidelines) > Search first: ClinVar, ClinGen, ACMG/AMP guidelines, VarSome
Variant type/class (missense, frameshift, nonsense, splice-site, structural)
Allele frequency in population databases > Search first: gnomAD, 1000 Genomes, ExAC, TOPMed, dbSNP
Somatic vs germline origin > Search first: COSMIC (somatic), ClinVar, ICGC, TCGA
Functional consequences (loss of function, gain of function, dominant negative)
Modifier Genes: Genes that modify disease severity or expression
Epigenetic Information: DNA methylation, histone modifications, chromatin changes affecting disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Chromosomal Abnormalities: Large-scale genetic changes (aneuploidy, translocations, inversions)

Search first: DECIPHER, ClinVar, ECARUCA, UCSC Genome Browser

5. Environmental Information

Environmental Factors: Non-genetic contributing factors (toxins, radiation, pollution, occupational exposure)

Search first: CTD (Comparative Toxicogenomics Database), TOXNET, PubMed, EPA databases
Lifestyle Factors: Behavioral factors (smoking, diet, exercise, alcohol consumption)

Search first: CDC databases, WHO, PubMed, NHANES
Infectious Agents: If applicable, pathogens causing or triggering disease (bacteria, viruses, fungi, parasites)

Search first: NCBI Taxonomy, ViPR, BV-BRC, MicrobeDB, GIDEON

6. Mechanism / Pathophysiology

Molecular Pathways: Specific signaling cascades or biochemical pathways involved (Wnt, MAPK, mTOR, PI3K-AKT, etc.)

Search first: KEGG, Reactome, WikiPathways, PathBank, BioCyc
Cellular Processes: Cell-level mechanisms (apoptosis, autophagy, cell cycle dysregulation, inflammation, etc.)

Search first: Gene Ontology (GO), Reactome, KEGG, PubMed
Protein Dysfunction: How protein structure or function is altered (misfolding, aggregation, loss of function, gain of function)

Search first: UniProt, PDB (Protein Data Bank), InterPro, Pfam, AlphaFold
Metabolic Changes: Alterations in metabolic processes (energy metabolism, lipid metabolism, amino acid metabolism)

Search first: KEGG, BioCyc, HMDB (Human Metabolome Database), BRENDA
Immune System Involvement: Role of immune response (autoimmunity, immunodeficiency, chronic inflammation)

Search first: ImmPort, Immunome Database, IEDB, Gene Ontology
Tissue Damage Mechanisms: How tissues/ are injured (oxidative stress, ischemia, fibrosis, necrosis)

Search first: PubMed, Gene Ontology, Reactome
Biochemical Abnormalities: Specific molecular defects (enzyme deficiencies, receptor dysfunction, ion channel defects)

Search first: BRENDA, UniProt, KEGG, OMIM, PubMed
Epigenetic Changes: DNA methylation, histone modifications affecting gene expression in disease

Search first: ENCODE, Roadmap Epigenomics, MethBase, DiseaseMeth
Molecular Profiling (if available):
Transcriptomics/gene expression changes > Search first: GEO (Gene Expression Omnibus), ArrayExpress, GTEx, Human Cell Atlas, SRA
Proteomics findings > Search first: PRIDE, ProteomeXchange, Human Protein Atlas, STRING, BioGRID
Metabolomics signatures > Search first: MetaboLights, Metabolomics Workbench, HMDB, METLIN
Lipidomics alterations > Search first: LIPID MAPS, SwissLipids, LipidHome, Metabolomics Workbench
Genomic structural features > Search first: UCSC Genome Browser, Ensembl, NCBI, dbVar, DGV
Advanced Technologies (if applicable):
Single-cell analysis findings (cell-type specific mechanisms, cellular heterogeneity) > Search first: Human Cell Atlas, Single Cell Portal, GEO, CELLxGENE
Spatial transcriptomics findings > Search first: GEO, Spatial Research, Vizgen, 10x Genomics data
Multi-omics integration results > Search first: TCGA, ICGC, cBioPortal, LinkedOmics, PubMed
Functional genomics screens (CRISPR, RNAi) > Search first: DepMap, GenomeRNAi, PubMed, BioGRID ORCS

For each mechanism, describe: - The causal chain from initial trigger to clinical manifestation - Which mechanisms are upstream vs downstream - What cell types and biological processes are involved - Suggest GO terms for biological processes and CL terms for cell types

7. Anatomical Structures Affected

Organ Level:
Primary organs directly affected
Secondary organ involvement (complications, secondary effects)
Body systems involved (cardiovascular, nervous, digestive, respiratory, endocrine, etc.)

Search first: Uberon, FMA (Foundational Model of Anatomy), OMIM, HPO, ICD-11, MeSH, SNOMED CT
Tissue and Cell Level:
Specific tissue types affected (epithelial, connective, muscle, nervous)
Specific cell populations targeted (with Cell Ontology terms)

Search first: Uberon, Human Protein Atlas, Cell Ontology, Human Cell Atlas, CellMarker, PanglaoDB
Subcellular Level:
Cellular compartments involved (mitochondria, nucleus, ER, lysosomes) (with GO Cellular Component terms)

Search first: Gene Ontology (Cellular Component), UniProt, Human Protein Atlas
Localization:
Specific anatomical sites (with UBERON terms) > Search first: FMA, Uberon, NeuroNames (for brain), SNOMED CT
Lateralization (unilateral, bilateral, asymmetric) > Search first: HPO, clinical literature, imaging databases

8. Temporal Development

Onset:
Typical age of onset (congenital, pediatric, adult, geriatric)
Onset pattern (acute, subacute, chronic, insidious)

Search first: OMIM, Orphanet, HPO, PubMed
Progression:
Disease stages (early, intermediate, advanced, end-stage) > Search first: Cancer Staging Manual (AJCC), WHO classifications, PubMed
Progression rate (rapid, slow, variable)
Disease course pattern (episodic, relapsing-remitting, progressive, stable)
Disease duration (self-limited, chronic lifelong)

Search first: Disease registries, longitudinal cohort databases, natural history studies, PubMed, Orphanet, OMIM
Patterns:
Remission patterns (spontaneous, treatment-induced) > Search first: Clinical trial databases, disease registries, PubMed
Critical periods (time windows of vulnerability or opportunity for intervention) > Search first: PubMed, developmental biology databases, clinical guidelines

9. Inheritance and Population

Epidemiology:
Prevalence (cases per 100,000 at given time)
Incidence (new cases per 100,000 per year)

Search first: Orphanet, CDC, WHO, GBD (Global Burden of Disease), national registries, SEER, disease registries
For Genetic Etiology:
Inheritance pattern (AD, AR, X-linked, mitochondrial, multifactorial, polygenic) > Search first: OMIM, Orphanet, ClinVar, GTR (Genetic Testing Registry)
Penetrance (complete, incomplete, age-dependent) > Search first: ClinVar, OMIM, PubMed, ClinGen
Expressivity (variable, consistent) > Search first: OMIM, ClinVar, PubMed
Genetic anticipation (increasing severity in successive generations) > Search first: OMIM, PubMed (especially for repeat expansion disorders)
Germline mosaicism > Search first: ClinVar, OMIM, genetic counseling literature, PubMed
Founder effects (population-specific mutations) > Search first: gnomAD, population genetics databases, PubMed
Consanguinity role > Search first: OMIM, population studies, genetic counseling resources
Carrier frequency > Search first: gnomAD, carrier screening databases, GeneReviews, GTR
Population Demographics:
Affected populations (ethnic or demographic groups with higher prevalence) > Search first: gnomAD, 1000 Genomes, PAGE Study, PubMed, population registries
Geographic distribution (endemic areas, regional variation) > Search first: WHO, CDC, GBD, Orphanet, geographic epidemiology databases
Geographic distribution of specific variants
Sex ratio (male:female) > Search first: Disease registries, OMIM, PubMed, epidemiological databases
Age distribution of affected individuals > Search first: CDC, disease registries, SEER, Orphanet

10. Diagnostics

Clinical Tests:
Laboratory tests (blood, urine, tissue chemistry, specific enzyme assays) > Search first: LOINC, LabTests Online, PubMed
Biomarkers (proteins, metabolites, genetic markers, circulating biomarkers) > Search first: FDA Biomarker List, BEST (Biomarkers, EndpointS, and other Tools), PubMed
Imaging studies (X-ray, CT, MRI, PET, ultrasound) > Search first: RadLex, DICOM, Radiopaedia, imaging databases
Functional tests (pulmonary function, cardiac stress tests) > Search first: LOINC, clinical guidelines, PubMed
Electrophysiology (EEG, EMG, ECG, nerve conduction studies) > Search first: LOINC, clinical neurophysiology databases, PubMed
Biopsy findings (histopathology, immunohistochemistry) > Search first: SNOMED CT, College of American Pathologists resources, PubMed
Pathology findings (microscopic examination) > Search first: SNOMED CT, Digital Pathology databases, PubMed
Genetic Testing:

Search first: GTR (Genetic Testing Registry), GeneReviews, ClinGen
Overview of recommended genetic testing approach
Whole genome sequencing (WGS) utility > Search first: GTR, ClinVar, GEL (Genomics England), gnomAD
Whole exome sequencing (WES) utility > Search first: GTR, ClinVar, OMIM, GeneMatcher
Gene panels (which panels, which genes) > Search first: GTR, ClinVar, laboratory-specific databases
Single gene testing > Search first: GTR, ClinVar, OMIM, GeneReviews
Chromosomal microarray (CMA) > Search first: DECIPHER, ClinVar, dbVar, ECARUCA
Karyotyping > Search first: Chromosome Abnormality Database, ClinVar, cytogenetics resources
FISH > Search first: ClinVar, cytogenetics databases, PubMed
Mitochondrial DNA testing > Search first: MITOMAP, MSeqDR, ClinVar, GTR
Repeat expansion testing > Search first: GTR, ClinVar, repeat expansion databases, PubMed
Omics-Based Diagnostics (if applicable):
RNA sequencing / transcriptomics > Search first: GEO, ArrayExpress, GTEx, RNA-seq databases
Proteomics > Search first: PRIDE, ProteomeXchange, FDA Biomarker database
Metabolomics > Search first: MetaboLights, Metabolomics Workbench, HMDB
Epigenomics > Search first: GEO, ENCODE, Roadmap Epigenomics, MethBase
Liquid biopsy > Search first: COSMIC, ClinVar, liquid biopsy databases, PubMed
Clinical Criteria:
Standardized diagnostic criteria (DSM, ICD, society guidelines) > Search first: DSM-5, ICD-11, clinical society guidelines, UpToDate
Differential diagnosis (other conditions to rule out, with distinguishing features) > Search first: DynaMed, UpToDate, clinical decision support systems
Screening:
Screening methods for asymptomatic individuals (newborn screening, carrier screening, cascade screening) > Search first: ACMG recommendations, CDC newborn screening, GTR

11. Outcome/Prognosis

Survival and Mortality:
Survival rate (5-year, 10-year, overall) > Search first: SEER, cancer registries, disease-specific registries, PubMed
Life expectancy (with and without treatment if applicable) > Search first: Orphanet, disease registries, actuarial databases, PubMed
Mortality rate > Search first: CDC, WHO, GBD, national mortality databases
Disease-specific mortality (deaths directly attributable to disease) > Search first: Disease registries, CDC Wonder, GBD, PubMed
Morbidity and Function:
Morbidity (disease-related disability and health impacts) > Search first: GBD, WHO, disability databases, PubMed
Disability outcomes (long-term functional impairments) > Search first: ICF (International Classification of Functioning), disability registries
Quality of life measures (EQ-5D, SF-36, PROMIS, disease-specific tools) > Search first: EQ-5D database, SF-36, PROMIS, PubMed
Disease Course:
Complications (secondary problems: infections, organ failure, etc.) > Search first: ICD codes, disease registries, clinical databases, PubMed
Recovery potential (likelihood and extent of recovery, with vs without treatment) > Search first: Natural history studies, rehabilitation databases, PubMed
Prediction:
Prognostic factors (age, disease severity, biomarkers, treatment response) > Search first: Prognostic models databases, clinical calculators, PubMed
Prognostic biomarkers (molecular markers predicting disease course) > Search first: FDA Biomarker database, PubMed, cancer prognostic databases

12. Treatment

Pharmacotherapy:
Pharmacological treatments (drug names, drug classes, mechanisms of action) > Search first: DrugBank, RxNorm, ATC classification, DailyMed, FDA databases
Pharmacogenomics (how genetic variants affect drug metabolism, efficacy, toxicity) > Search first: PharmGKB, CPIC (Clinical Pharmacogenetics), FDA Table of PGx Biomarkers
Advanced Therapeutics:
Gene therapy (viral vectors, CRISPR, gene replacement, gene editing) > Search first: ClinicalTrials.gov, FDA gene therapy database, ASGCT resources
Cell therapy (stem cell transplant, CAR-T, cellular therapeutics) > Search first: ClinicalTrials.gov, FDA cell therapy database, FACT standards
RNA-based therapies (ASOs, siRNA, mRNA therapies) > Search first: ClinicalTrials.gov, FDA approvals, PubMed
Targeted therapies (treatments directed at specific molecular targets) > Search first: My Cancer Genome, OncoKB, ClinicalTrials.gov, FDA approvals
Immunotherapies (checkpoint inhibitors, monoclonal antibodies) > Search first: Cancer Immunotherapy Database, FDA approvals, ClinicalTrials.gov
Surgical and Interventional:
Surgical interventions (types of surgery, timing, outcomes) > Search first: CPT codes, surgical registries, clinical guidelines, PubMed
Supportive and Rehabilitative:
Supportive care (symptom management, pain control, nutrition) > Search first: Clinical guidelines, Cochrane Library, PubMed
Rehabilitation (physical therapy, occupational therapy, speech therapy) > Search first: Rehabilitation medicine databases, clinical guidelines, PubMed
Experimental:
Experimental treatments in clinical trials (with NCT identifiers if available) > Search first: ClinicalTrials.gov, EU Clinical Trials Register, WHO ICTRP
Treatment Outcomes:
Treatment response rates > Search first: Clinical trial databases, FDA reviews, systematic reviews, PubMed
Side effects and adverse events > Search first: FDA Adverse Event Reporting System (FAERS), MedWatch, PubMed
Treatment Strategy:
Treatment algorithms (clinical pathways, decision trees) > Search first: Clinical practice guidelines, NCCN Guidelines, UpToDate
Combination therapies > Search first: ClinicalTrials.gov, treatment guidelines, PubMed
Personalized medicine approaches (genotype-guided treatment) > Search first: My Cancer Genome, CIViC, PharmGKB, precision medicine databases

For each treatment, suggest NCIT (NCI Thesaurus) clinical-intervention terms where applicable.

13. Prevention

Prevention Levels:
Primary prevention (preventing disease occurrence: vaccination, risk factor modification) > Search first: CDC, WHO, USPSTF recommendations, Cochrane Library
Secondary prevention (early detection and treatment: screening programs, early intervention) > Search first: USPSTF, CDC screening guidelines, WHO
Tertiary prevention (preventing complications in those with disease) > Search first: Clinical guidelines, disease management protocols, PubMed
Immunization: Vaccine strategies (if applicable)

Search first: CDC vaccine schedules, WHO immunization, FDA vaccine database
Screening and Early Detection:
Screening programs (population-based: newborn screening, cancer screening) > Search first: CDC screening programs, USPSTF, cancer screening databases
Genetic screening (carrier screening, preimplantation genetic diagnosis, prenatal testing) > Search first: ACMG recommendations, ACOG guidelines, GTR
Risk stratification (identifying high-risk individuals for targeted prevention) > Search first: Risk prediction models, clinical calculators, PubMed
Behavioral Interventions: Lifestyle modifications to reduce risk

Search first: CDC, WHO, behavioral intervention databases, Cochrane Library
Counseling: Genetic counseling (risk assessment, family planning guidance)

Search first: NSGC resources, ACMG guidelines, GeneReviews
Public Health:
Public health interventions (sanitation, vector control, health education) > Search first: CDC, WHO, public health databases, PubMed
Environmental interventions (reducing environmental risk factors) > Search first: EPA databases, WHO environmental health, PubMed
Prophylaxis: Preventive medications or procedures

Search first: Clinical guidelines, FDA approvals, PubMed

14. Other Species / Natural Disease

Taxonomy: Species affected (with NCBI Taxon identifiers)

Search first: NCBI Taxonomy
Breed: Specific breeds affected (with VBO identifiers if applicable)

Search first: VBO (Vertebrate Breed Ontology)
Gene: Orthologous genes in other species (with NCBI Gene IDs)

Search first: NCBI Gene
Natural Disease:
Naturally occurring disease in other species (companion animals, wildlife) > Search first: OMIA (Online Mendelian Inheritance in Animals), VetCompass, PubMed
Veterinary relevance and importance in animal health > Search first: OMIA, veterinary databases, PubMed
Comparative Biology:
Comparative pathology (similarities and differences across species) > Search first: OMIA, comparative pathology databases, PubMed
Evolutionary conservation of disease mechanisms > Search first: HomoloGene, OrthoMCL, Alliance of Genome Resources
Transmission (if applicable):
Zoonotic potential > Search first: CDC zoonotic diseases, WHO zoonoses, GIDEON
Cross-species susceptibility > Search first: NCBI Taxonomy, veterinary databases, PubMed

15. Model Organisms

Model Types:
Model organism type (mammalian, invertebrate, cellular, in vitro) > Search first: Alliance of Genome Resources, model organism databases
Specific model systems (mouse, rat, zebrafish, Drosophila, C. elegans, yeast, cell lines, organoids, iPSCs) > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, SGD, ATCC, Cellosaurus
Induced models (drug treatment, surgical intervention, environmental manipulation) > Search first: MGI, model organism databases, PubMed
Genetic Models:
Types available (knockout, knock-in, transgenic, conditional, humanized) > Search first: MGI, IMPC, KOMP, EuMMCR, IMSR
Model Characteristics:
Phenotype recapitulation (how well model reproduces human disease features) > Search first: Model organism databases, comparative studies, PubMed
Model limitations (aspects of human disease not captured) > Search first: Model organism databases, PubMed, review articles
Applications:
Research applications (what aspects of disease can be studied) > Search first: Model organism databases, PubMed
Resources:
Model databases > Search first: MGI, RGD, ZFIN, FlyBase, WormBase, IMSR, EMMA, MMRRC

Citation Requirements

Cite primary literature (PMID preferred) for all mechanistic and clinical claims
Prioritize recent reviews and landmark papers
Include direct quotes from abstracts where possible to support key statements
Distinguish evidence source types: human clinical, model organism, in vitro, computational

Output Format

Structure your response as a comprehensive narrative organized by the sections above. For each section, provide: - Factual content with specific details (numbers, percentages, gene names, variant nomenclature) - Ontology term suggestions (HPO, GO, CL, UBERON, CHEBI, NCIT, MONDO) where applicable - Evidence citations with PMIDs - Direct quotes from abstracts to support key claims - Clear indication when information is not available or not applicable for this disease

This report will be used to populate a disease knowledge base entry with: - Pathophysiology descriptions with causal chains - Gene/protein annotations (HGNC, GO terms) - Phenotype associations (HP terms) with frequencies - Cell type involvement (CL terms) - Anatomical locations (UBERON terms) - Chemical entities (CHEBI terms) - Treatment annotations (NCIT terms) - Evidence items with PMIDs and exact abstract quotes - Epidemiology, prognosis, diagnostic, and prevention information - Animal model descriptions with phenotype recapitulation details

Sarcoglycanopathy: comprehensive disease-characteristics report

Executive summary

Sarcoglycanopathy is a collective term for four autosomal-recessive muscular dystrophies caused by biallelic pathogenic variants in SGCA, SGCB, SGCG, or SGCD. Their products—α-, β-, γ-, and δ-sarcoglycan—form a transmembrane subcomplex of the dystrophin-associated protein complex (DAPC). Loss of one component commonly destabilizes the others, weakening the sarcolemma during contraction and initiating myofiber injury, inflammation, fibrosis, and fatty replacement. Clinical severity ranges from asymptomatic hyperCKemia or adult-onset limb-girdle weakness to a Duchenne-like childhood disorder with loss of walking in adolescence, respiratory failure, and dilated cardiomyopathy. Cognitive impairment is not characteristic. (barba2023modelingsarcoglycanopathyin pages 1-2, guimaraescosta2021clinicalcorrelationsand pages 1-3)

The most important recent clinical development is systemic SGCB replacement with bidridistrogene xeboparvovec. In a six-patient phase 1/2 study published January 4, 2024, mean β-sarcoglycan expression reached 36.2% and 62.1% of normal at day 60 in low- and high-dose cohorts, respectively, with preliminary motor improvements maintained through two years. The study was small, open-label, and nonrandomized, so efficacy remains provisional. (mendell2024genetherapywith pages 1-2, mendell2024genetherapywith pages 7-8)

Current subtype / legacy name	Causal gene / protein	Inheritance	Hallmark severity / onset	Cardiac / respiratory notes	Key evidence / statistics
LGMDR3 / LGMD2D	SGCA / α-sarcoglycan	Autosomal recessive	In the 100-patient sarcoglycanopathy cohort, α-SG cases had later mean onset than γ-SG: 8.0 years; phenotype is variable from severe childhood-onset to milder late-onset forms. Earlier onset predicts earlier loss of ambulation. (guimaraescosta2021clinicalcorrelationsand pages 1-3)	Dilated cardiomyopathy can occur across all sarcoglycanopathy subtypes; heart and respiratory surveillance are recommended. (guimaraescosta2021clinicalcorrelationsand pages 1-3, barba2023modelingsarcoglycanopathyin pages 1-2)	α-SG was one of the major subtypes in the 100-patient cohort (41/100). In the broader Dutch AR-LGMD/Miyoshi cohort, sarcoglycanopathies represented 67/244 (27%) of cases. (guimaraescosta2021clinicalcorrelationsand pages 1-3)
LGMDR4 / LGMD2E	SGCB / β-sarcoglycan	Autosomal recessive	Often severe, but heterogeneous. In one 32-patient series, phenotypes were 15 severe, 12 mild, 5 unknown; another multicenter cohort reported mean onset around 24.4 years for β-SG cases represented there, highlighting variability and probable ascertainment effects. (semplicini2015clinicalandgenetic pages 2-3, guimaraescosta2021clinicalcorrelationsand pages 1-3)	Cardiac involvement is prominent: 63% had cardiac involvement, 19% dilated cardiomyopathy, 28% rhythm abnormalities; 19% required respiratory support. Constant surveillance is emphasized, especially for LGMDR4. (semplicini2015clinicalandgenetic pages 2-3, barba2023modelingsarcoglycanopathyin pages 1-2)	Estimated prevalence reported as 0.86 × 10⁻⁶. First-in-human SGCB gene therapy trial enrolled 6 patients aged 4–15 years; Day-60 SGCB expression reached 36.2% and 62.1% of normal in low/high dose cohorts, respectively. (semplicini2015clinicalandgenetic pages 2-3, mendell2024genetherapywith pages 1-2, NCT03652259 chunk 1)
LGMDR5 / LGMD2C	SGCG / γ-sarcoglycan	Autosomal recessive	Typically earlier and more severe. In the 100-patient cohort, γ-SG cases had mean onset 5.5 years and more frequent severe progression with early loss of ambulation. (guimaraescosta2021clinicalcorrelationsand pages 1-3)	Dilated cardiomyopathy occurred in all subtypes and was reported especially in γ-SG patients; respiratory problems needing ventilation are common in sarcoglycanopathy overall. (guimaraescosta2021clinicalcorrelationsand pages 1-3, barba2023modelingsarcoglycanopathyin pages 1-2)	In the French multicenter cohort, γ-SG was the largest subgroup (54/100); >90% carried the homozygous c.525delT frameshift variant, indicating a strong founder effect in some populations. (guimaraescosta2021clinicalcorrelationsand pages 1-3)
LGMDR6 / LGMD2F	SGCD / δ-sarcoglycan	Autosomal recessive	Ultra-rare and generally severe/rapidly progressive. In the largest international cohort, 60% were wheelchair-bound from early teens with median loss of ambulation at 12.0 years; distal weakness appeared early in 56.5%. Absent sarcoglycan expression predicted earlier onset and ambulation loss. (alonsoperez2022clinicalandgenetic pages 1-1, alonsoperez2022clinicalandgenetic pages 2-3)	Cardiac involvement in 21.7% (5/23); 17.4% (4/23) required non-invasive ventilation. Surveillance is recommended, especially because cardiomyopathy can occur across sarcoglycanopathies. (alonsoperez2022clinicalandgenetic pages 1-1, barba2023modelingsarcoglycanopathyin pages 1-2)	Largest cohort identified 23 analyzed patients from 18 families across 9 countries; 87% had consanguineous parents, supporting enrichment in consanguineous settings. Geographic concentration has been noted in Brazil. (alonsoperez2022clinicalandgenetic pages 2-3, guimaraescosta2021clinicalcorrelationsand pages 1-3)

Table: This table summarizes the four canonical sarcoglycanopathy subtypes for knowledge-base use, linking nomenclature, gene/protein, inheritance, and major clinical distinctions. It highlights the strongest gathered quantitative evidence on onset, severity, and cardio-respiratory burden.

1. Disease information

Definition and identifiers

Preferred name: sarcoglycanopathy; MONDO:0016140.
MeSH: Sarcoglycanopathies, D058088; parent term Muscular Dystrophies, Limb-Girdle, D049288. (OpenTargets Search: sarcoglycanopathy, NCT04475926 chunk 2)
Orphanet umbrella concept: qualitative or quantitative defects of sarcoglycan, ORPHA:207052. (OpenTargets Search: sarcoglycanopathy)
ICD: ICD-10 does not provide a reliable gene-specific code; coding usually falls under muscular dystrophy (for example G71.0 in ICD-10-CM, depending on jurisdiction). ICD-11 should be recorded under the relevant inherited muscular-dystrophy category, with the molecular subtype represented separately.
Canonical subtypes: LGMDR3 α-sarcoglycan-related (legacy LGMD2D), LGMDR4 β-sarcoglycan-related (LGMD2E), LGMDR5 γ-sarcoglycan-related (LGMD2C), and LGMDR6 δ-sarcoglycan-related (LGMD2F). (barba2023modelingsarcoglycanopathyin pages 1-2)
Common synonyms: sarcoglycan muscular dystrophy, sarcoglycan-deficient muscular dystrophy, autosomal-recessive limb-girdle muscular dystrophy 3–6, α/β/γ/δ-sarcoglycanopathy, and severe childhood autosomal-recessive muscular dystrophy.

This report synthesizes aggregated disease-level resources and published cohorts, not individual EHR records. The strongest human datasets include a 100-patient multicenter series and subtype-specific cohorts; therefore, frequencies should not be interpreted as population-screening estimates. (alonsoperez2022clinicalandgenetic pages 1-1, guimaraescosta2021clinicalcorrelationsand pages 1-3)

2. Etiology, risk, protection, and gene–environment interaction

Causal factors

The primary cause is germline biallelic loss of sarcoglycan function. Approximately 67% of reported causal variants are missense variants, followed by frameshift and null alleles. Null/out-of-frame variants generally produce the greatest disruption of complex biogenesis. Missense proteins may misfold and be prematurely eliminated through endoplasmic-reticulum-associated degradation (ERAD). (barba2023modelingsarcoglycanopathyin pages 1-2)

Risk factors

Genetic: two pathogenic/likely pathogenic alleles in the same sarcoglycan gene; absent residual protein and onset before age 10 predict severe disease. (alonsoperez2022clinicalandgenetic pages 1-1, alonsoperez2022clinicalandgenetic pages 2-3)
Family history/consanguinity: as expected for recessive disease, consanguinity increases the probability of homozygosity. In the international LGMDR6 cohort, 87% had consanguineous parents. (alonsoperez2022clinicalandgenetic pages 1-1)
Founder effects: more than 90% of γ-sarcoglycan cases in one French/North-African-enriched cohort carried homozygous SGCG c.525delT. (guimaraescosta2021clinicalcorrelationsand pages 1-3)
Sex: both sexes are affected; there is no established sex-specific penetrance.
Mechanical loading: contraction is not the genetic cause, but repeated mechanical stress exposes sarcolemmal fragility. In knockout zebrafish, viscous-medium swimming accelerated phenotype appearance, providing experimental evidence of a load–genotype interaction. (barba2023modelingsarcoglycanopathyin pages 1-2)

No validated environmental toxin, infection, diet, smoking exposure, protective allele, or disease-preventing lifestyle factor has been established. Avoiding extreme eccentric or exhaustion exercise is prudent after diagnosis, but ordinary activity is not a cause. Evidence for specific modifier genes, epigenetic protective factors, or reproducible human G×E effects remains insufficient.

3. Phenotypes

Core phenotype and suggested HPO annotations

Progressive proximal weakness—pelvic before or with shoulder-girdle involvement; difficulty running, climbing stairs, rising from the floor, and frequent falls. Suggested terms: HP:0003324 (generalized muscle weakness), HP:0008994 (proximal muscle weakness), HP:0003560 (muscular dystrophy).
Axial weakness and contractures are frequent; suggested HP:0003701 (proximal muscle weakness), HP:0001371 (flexion contracture), and HP:0003306 (spinal rigidity), where applicable. (guimaraescosta2021clinicalcorrelationsand pages 1-3)
Calf hypertrophy, scapular winging, lumbar lordosis, waddling gait, and Gowers sign are common dystrophic manifestations; suggested HP:0008981, HP:0003691, HP:0002937, HP:0002515, and HP:0003391, respectively.
HyperCKemia: frequently marked and may precede weakness; HP:0003236. CK can decline late as muscle mass is lost, so a falling CK is not necessarily improvement.
Loss of ambulation: HP:0002355. At mean 22.9-year follow-up, 65.3% of a 100-patient cohort were wheelchair-dependent; six had died. (guimaraescosta2021clinicalcorrelationsand pages 1-3)
Respiratory muscle weakness/restrictive ventilatory defect: HP:0002747, HP:0002093. Thirty of 100 patients in the multicenter cohort were ventilated. In LGMDR6, 17.4% required non-invasive ventilation. (alonsoperez2022clinicalandgenetic pages 1-1, guimaraescosta2021clinicalcorrelationsand pages 1-3)
Dilated cardiomyopathy and rhythm disturbance: HP:0001644, HP:0011675, HP:0010987. Cardiac disease can occur in every subtype. In a 32-person LGMDR4 cohort, 63% had cardiac involvement, including DCM in 19% and rhythm abnormalities in 28%. (semplicini2015clinicalandgenetic pages 2-3)
Distal weakness: usually secondary but can appear early, particularly in LGMDR6, where it occurred in 56.5%. HP:0002460. (alonsoperez2022clinicalandgenetic pages 1-1)
Cognition: intellectual disability is not a characteristic phenotype; the 2023 model review states, “Cognitive impairment has never been reported.” (barba2023modelingsarcoglycanopathyin pages 1-2)

Onset is usually insidious in childhood, but expression is highly variable. In the 100-patient cohort, median/mean reported onset differed substantially: γ-SG 5.5 years, α-SG 8 years, and β-SG 24.4 years. These figures are cohort-dependent and do not imply that β-sarcoglycanopathy is usually benign. (guimaraescosta2021clinicalcorrelationsand pages 1-3)

Quality of life

Weakness progressively limits mobility, self-care, education/employment, community participation, and independence; ventilation and cardiomyopathy add treatment burden. Disease-specific EQ-5D/SF-36 reference values and per-phenotype utilities are not well established. Current prospective studies instead emphasize NSAD, PUL, timed motor tests, FVC, and wearable mobility measures. (NCT04475926 chunk 1, NCT05876780 chunk 1)

4. Genetic and molecular information

Subtype	Gene/protein	Useful identifiers	Typical molecular consequence
LGMDR3/2D	SGCA, α-SG	HGNC:6615; OMIM gene 600119; phenotype 253600	Usually loss/reduction or mislocalization of α-SG; secondary complex deficiency
LGMDR4/2E	SGCB, β-SG	HGNC:10806; OMIM gene 600900; phenotype 604286	Loss of β-SG and destabilization of associated SGs
LGMDR5/2C	SGCG, γ-SG	HGNC:10809; OMIM gene 608896; phenotype 253700	Loss of γ-SG; severe founder-associated disease is common in some populations
LGMDR6/2F	SGCD, δ-SG	HGNC:10807; OMIM gene 601411; phenotype 601287	Loss/misfolding of δ-SG; skeletal and cardiac membrane dysfunction

Open Targets independently identifies SGCA, SGCB, SGCG, and SGCD as the four leading sarcoglycanopathy-associated targets. (OpenTargets Search: sarcoglycanopathy)

Variants include missense, nonsense, frameshift, canonical splice, exon-level deletion/duplication, and rarer structural alleles. They are constitutional germline, not somatic. Most act through loss of function, abnormal folding/trafficking, ERAD, or failure to assemble the tetramer; gain-of-function and dominant-negative mechanisms are not established as the canonical cause. Variant interpretation should use ACMG/AMP criteria, segregation, population frequency, phenotype, RNA studies where relevant, and muscle protein expression. A VUS alone does not establish diagnosis.

Population allele frequencies must be reported variant by variant from the current gnomAD release; no single meaningful frequency applies to a gene. Pathogenic alleles are individually rare, while founder variants can be locally enriched. No recurrent aneuploidy, translocation, anticipation mechanism, or characteristic epigenetic lesion defines the disease. Germline mosaicism is theoretically possible but is not a major documented mechanism.

5. Environmental, lifestyle, and infectious information

There is no evidence that sarcoglycanopathy is caused by toxins, radiation, pollution, occupation, diet, alcohol, smoking, or infection. Exercise modifies mechanical demand on vulnerable muscle: individualized low-to-moderate aerobic and submaximal activity is generally favored, whereas unaccustomed high-intensity eccentric exercise may increase injury. Respiratory vaccination, nutrition, and weight management prevent complications rather than the inherited disease itself. The condition is noninfectious and nontransmissible.

6. Mechanism and pathophysiology

Causal chain

Upstream genetic defect: biallelic SGCA/B/G/D variant.
Protein defect: absent, unstable, misfolded, or mistargeted sarcoglycan; secondary loss of interacting partners.
Complex failure: reduced sarcoglycan–sarcospan/DAPC function at the sarcolemma.
Biomechanical injury: contraction-induced membrane instability and abnormal permeability.
Downstream responses: ionic dysregulation, myofiber necrosis, damage-associated signaling, immune-cell recruitment, repeated regeneration, oxidative/mitochondrial stress.
Tissue remodeling: fibrosis and adipose replacement reduce contractile tissue.
Clinical output: progressive skeletal weakness, respiratory restriction, and—depending on genotype—cardiomyopathy/arrhythmia. (barba2023modelingsarcoglycanopathyin pages 1-2, barba2023modelingsarcoglycanopathyin pages 6-9)

The 2023 primary zebrafish paper states that SGs form a tetramer in the DAPC, which “plays a key role in protecting sarcolemma from stress deriving from muscle contraction.” It also showed that a δ-SG missense protein was an ERAD substrate, supporting misfolding and premature degradation as a distinct upstream mechanism. (barba2023modelingsarcoglycanopathyin pages 1-2)

Adult sgcd-null zebrafish developed disorganized fibers, myofibrillar fragmentation, hypercontracted fibers, inflammatory L-plastin-positive cells, fibrosis, adipose replacement, and progressively abnormal mitochondria. These findings support inflammation, fibrosis, and mitochondrial injury as downstream—not initiating—processes. (barba2023modelingsarcoglycanopathyin pages 6-9)

Suggested GO terms: sarcolemma organization (GO:0042383), muscle contraction (GO:0006936), regulation of membrane integrity, protein quality control/ERAD (GO:0036503), inflammatory response (GO:0006954), muscle-cell apoptosis/necrosis, extracellular-matrix organization (GO:0030198), and muscle-organ development (GO:0007517). Suggested cellular components include sarcolemma (GO:0042383) and dystrophin-associated glycoprotein complex. Suggested cell types: skeletal-muscle fiber/myocyte (CL:0000188), cardiomyocyte (CL:0000746), satellite cell (CL:0000596), fibroblast (CL:0000057), and macrophage (CL:0000235).

Disease-specific human single-cell, spatial-transcriptomic, metabolomic, lipidomic, and epigenomic signatures are not yet mature enough for routine knowledge-base assertions. Available molecular profiling is dominated by biopsy protein expression and preclinical histology.

7. Anatomical structures affected

Primary organ/tissue: bilateral skeletal muscle, especially pelvic-girdle, thigh, shoulder-girdle, axial, and respiratory muscles. Suggested UBERON: skeletal muscle organ UBERON:0001630, diaphragm UBERON:0001103, heart UBERON:0000948.
Secondary/variable: myocardium and cardiac conduction system; diaphragm/intercostal muscles; tendons and joints through contracture; spine through lordosis/scoliosis.
Cellular target: multinucleated skeletal myofibers and cardiomyocytes; macrophages and fibroblasts participate secondarily.
Subcellular localization: sarcolemma/DAPC; ER and proteasome become relevant for misfolded variants; mitochondria show downstream injury. (barba2023modelingsarcoglycanopathyin pages 6-9, barba2023modelingsarcoglycanopathyin pages 1-2)
Lateralization: usually symmetric; marked unilateral disease is atypical and should prompt reconsideration.

8. Temporal development

The disorder is chronic, lifelong, and usually progressive rather than episodic or relapsing. Early disease features running difficulty, Gowers maneuver, stair-climbing difficulty, hyperCKemia, and calf enlargement. Intermediate disease brings contractures, axial/upper-limb weakness, and declining timed function. Advanced disease includes loss of ambulation, restrictive respiratory insufficiency, and possible cardiomyopathy.

Age at onset is the strongest repeatedly observed clinical predictor. In the 100-person study, younger onset independently predicted severity and time to loss of ambulation; absent biopsy protein also predicted earlier loss of walking. (guimaraescosta2021clinicalcorrelationsand pages 1-3) LGMDR6 illustrates the severe end: 60% were wheelchair-bound in the early teens, at median age 12. (alonsoperez2022clinicalandgenetic pages 1-1)

There is no spontaneous remission. The critical therapeutic window is probably before extensive fibrofatty replacement, because gene replacement can restore protein but cannot readily replace lost contractile tissue. This is a biologically strong inference rather than a proven age cutoff.

9. Inheritance and population

Inheritance is autosomal recessive. For two confirmed carrier parents, each pregnancy has a 25% affected, 50% carrier, and 25% unaffected/non-carrier probability. Penetrance of clearly deleterious biallelic genotypes is generally high but may be age-dependent; expressivity is markedly variable. Anticipation is not expected.

Sarcoglycanopathies are ultra-rare, and incidence is not reliably quantified. A β-sarcoglycanopathy series cited an estimated prevalence of 0.86 per million. In a Dutch clinically ascertained cohort, sarcoglycanopathies constituted 67/244 (27%) of molecularly diagnosed AR-LGMD/Miyoshi cases; this is a diagnostic mix, not population prevalence. (semplicini2015clinicalandgenetic pages 2-3, guimaraescosta2021clinicalcorrelationsand pages 1-3)

Geographic enrichment differs: α-SG is prominent in Europe, γ-SG in North Africa, β-SG occurs worldwide, and reported δ-SG cases have been concentrated in Brazil. These patterns reflect founder alleles, ascertainment, and consanguinity rather than ethnic restriction. (guimaraescosta2021clinicalcorrelationsand pages 1-3) Both sexes are affected approximately equally.

10. Diagnostics

Recommended approach

Clinical suspicion: symmetric proximal weakness, Gowers sign, calf enlargement, contractures, markedly elevated CK, recessive pedigree, or incidental hyperCKemia.
Baseline laboratory testing: serum CK, AST/ALT, LDH, aldolase where available; muscle-derived transaminase elevation should not automatically be labeled hepatic disease.
Molecular confirmation: an NGS neuromuscular/LGMD panel containing SGCA, SGCB, SGCG, SGCD, with deletion/duplication analysis. WES or WGS is appropriate if panel testing is negative, the phenotype is atypical, or structural/noncoding variation is suspected. A Dutch study using sequential targeted testing, panels, and WES achieved diagnoses in 57/60 families with available DNA. (guimaraescosta2021clinicalcorrelationsand pages 1-3)
RNA analysis: useful for uncertain splice variants; muscle RNA may be necessary.
Muscle biopsy: now usually second-line, but valuable when genetics is unresolved or functional validation is needed. Histology is dystrophic, with necrosis/regeneration and fibrofatty change. Immunohistochemistry or Western blot should assess all four sarcoglycans because secondary deficiency can obscure which gene is primary. Residual expression has prognostic value. (alonsoperez2022clinicalandgenetic pages 1-1, semplicini2015clinicalandgenetic pages 2-3)
Cardiac assessment: ECG, echocardiography, and ambulatory rhythm monitoring; cardiac MRI when indicated.
Respiratory assessment: seated and supine FVC, maximal inspiratory/expiratory pressures, peak cough flow, nocturnal oximetry/capnography or sleep study when symptoms or declining function warrant.
Functional/imaging biomarkers: NSAD, PUL 2.0, 10- and 100-m walk/run, rise-from-floor, stair climb, TUG, and quantitative muscle MRI fat fraction. These are being implemented in prospective natural-history and gene-therapy studies. (NCT04475926 chunk 1, NCT05876780 chunk 1, NCT06246513 chunk 1)

CMA, karyotyping, FISH, mitochondrial DNA testing, and repeat-expansion testing are not first-line unless another diagnosis is suspected. Differential diagnoses include dystrophinopathy, FKRP-related disease, calpainopathy, dysferlinopathy, anoctaminopathy, dystroglycanopathy, Pompe disease, spinal muscular atrophy, congenital myopathy, and inflammatory myopathy.

Cascade testing should be offered to relatives after identifying familial variants. Population newborn screening is not standard; CK-first newborn approaches remain investigational. Carrier, prenatal, and preimplantation genetic testing are feasible once familial pathogenic variants are known.

11. Outcome and prognosis

Prognosis is determined chiefly by age at onset, residual sarcoglycan expression, genotype, and cardiac/respiratory involvement. In the 100-person cohort, 65.3% were wheelchair-bound after mean follow-up of 22.9 years, 30 required ventilation, and six died. (guimaraescosta2021clinicalcorrelationsand pages 1-3) In LGMDR4, CK, pulmonary function, and left-ventricular function declined in parallel with age, and ejection fraction was the strongest independent progression variable in one 26-patient analysis. (semplicini2015clinicalandgenetic pages 2-3)

No robust universal 5- or 10-year survival estimate exists. Severe childhood disease can cause major disability by adolescence and premature death from respiratory failure or cardiomyopathy; mild patients may remain ambulant into late adulthood. Recovery of established weakness is uncommon with supportive care, but complications can be delayed or treated. Formal sarcoglycanopathy-specific EQ-5D, SF-36, and PROMIS benchmarks remain a research gap.

12. Treatment and current applications

Present standard of care

No gene-specific drug is yet established as routine curative therapy. Management is multidisciplinary:

individualized physical and occupational therapy, stretching, orthoses, mobility aids, seating, and contracture prevention;
low-to-moderate, non-exhaustive activity; avoid prolonged immobilization and excessive eccentric loading;
respiratory physiotherapy, assisted cough, non-invasive ventilation, and prompt treatment of infections;
standard guideline-directed cardiomyopathy/arrhythmia therapy—commonly ACE inhibitor/ARB/ARNI, β-blocker, mineralocorticoid antagonist, and device therapy when clinically indicated;
nutrition, bone health, pain management, psychosocial support, anesthesia planning, and orthopedic intervention for function-threatening contracture or scoliosis.

Suggested NCIt intervention concepts include physical therapy, occupational therapy, noninvasive positive-pressure ventilation, assisted coughing, genetic counseling, AAV gene therapy, prednisone, and cardiac transplantation. Drug-level pharmacogenomic guidance specific to sarcoglycanopathy is unavailable.

Pharmacotherapy

Glucocorticoids are not supported by the same evidence base as in Duchenne dystrophy. A small exploratory study of 19 genetically heterogeneous LGMD patients receiving weekly prednisone for 24 weeks found acceptable safety, reduced CK, and a trend toward motor improvement; it does not establish efficacy for sarcoglycanopathy. (andrea2024molecularmechanismsand pages 18-19)

Gene and molecular therapy

Bidridistrogene xeboparvovec (SRP-9003; scAAVrh74.MHCK7.hSGCB). Six children aged 4–15 years received one IV dose: 1.85×10^13 vg/kg (n=3) or 7.41×10^13 vg/kg (n=3). Day-60 mean β-SG expression was 36.2% and 62.1% of normal; β-SG-positive fibers were 51% and 72%. At year 2, expression remained 54.0% and 60.3%, and year-1 NSAD improved by 5.7 and 4.0 points. (mendell2024genetherapywith pages 1-2, mendell2024genetherapywith pages 3-4, mendell2024genetherapywith pages 4-5)

The abstract reports: “The 2-year safety and efficacy of bidridistrogene xeboparvovec support clinical development advancement. Further studies are necessary to confirm the long-term safety and efficacy.” Vomiting occurred in 4/6, increased GGT in 3/6, and one patient developed AAV-related hepatitis requiring four days of hospitalization; serious events resolved with standard therapy. PMID 38177855; published online 2024-01-04; https://doi.org/10.1038/s41591-023-02730-9. (mendell2024genetherapywith pages 1-2, mendell2024genetherapywith pages 9-10, mendell2024genetherapywith pages 3-4, NCT03652259 chunk 1)

Key caveats are the tiny sample, open-label/nonrandomized design, post-hoc functional analysis, and unmatched natural-history comparators. (mendell2024genetherapywith pages 7-8)

Active development:

NCT05876780: phase 1 SRP-9003 study in ambulatory and nonambulatory LGMDR4, six participants, with day-60 and month-24 protein endpoints and five-year follow-up. (NCT05876780 chunk 1)
NCT06246513/EMERGENE: multinational phase 3, 17 participants, single SRP-9003 infusion plus prophylactic prednisone; primary day-60 β-SG-positive-fiber endpoint, with NSAD/PUL and safety through month 60. Trial began January 15, 2024. (NCT06246513 chunk 1)
NCT05973630: ATA-200, an AAV vector carrying human SGCG, phase 1 for ambulant children with LGMDR5; four participants receive 1.0×10^14 vg/kg IV with five-year follow-up. (NCT05973630 chunk 1)
NCT04475926/Journey: prospective natural history, 205 participants across LGMDR3–5 and calpainopathy, measuring NSAD, PUL, timed function, ROM, and FVC for up to five years. (NCT04475926 chunk 1)

Earlier isolated-limb SGCA transfer produced only modest expression and inconsistent function. Preclinical AAV-SGCA/SGCG studies improved protein expression, histology, force, motor function, and CK in knockout mice. Exon skipping for selected SGCG variants and mesoangioblast therapy remain preclinical. (andrea2024molecularmechanismsand pages 18-19)

13. Prevention

Primary prevention by lifestyle or vaccination is impossible because the initiating defect is inherited. Reproductive prevention options include carrier testing, partner testing, cascade screening, preimplantation genetic testing, chorionic-villus sampling, and amniocentesis after counseling. Secondary prevention consists of early molecular diagnosis and presymptomatic cardiac/respiratory surveillance. Tertiary prevention includes stretching, safe activity, vaccinations, airway clearance, timely ventilation, cardioprotective therapy, fall prevention, and avoidance of prolonged immobility. There is no disease-specific vaccine or preventive medication.

14. Other species and natural disease

Orthologous sarcoglycan disease occurs naturally in several mammals. The best-established comparative systems include δ-sarcoglycan-deficient Syrian hamsters with cardiomyopathy and muscular dystrophy and naturally occurring canine sarcoglycan deficiencies. Their pathology supports evolutionary conservation of DAPC-mediated membrane stabilization. Veterinary disease is inherited and nonzoonotic; there is no cross-species transmission. Relevant taxa include Mus musculus (NCBI Taxon 10090), Danio rerio (7955), Mesocricetus auratus (10036), and Canis lupus familiaris (9615). Breed-specific assertions should be linked to OMIA/VBO records rather than generalized across dogs.

15. Model organisms and experimental systems

Mouse: Sgca, Sgcb, Sgcg, and Sgcd knockout models reproduce progressive skeletal dystrophy. β-, γ-, and δ-SG-null mice develop dilated or hypertrophic cardiomyopathy, whereas α-SG-null mice generally do not—an important limitation and genotype-specific strength. (barba2023modelingsarcoglycanopathyin pages 1-2)
Zebrafish: CRISPR sgcb−/− and sgcd−/− lines progress from mild larval impairment to adult myopathy and cardiac disease. The models reproduce fiber disarray, inflammation, fibrosis, adipose replacement, and mitochondrial injury and permit high-throughput drug screening. Mechanical challenge accelerates phenotype onset. Published 2023-08-11; https://doi.org/10.3390/ijms241612707. (barba2023modelingsarcoglycanopathyin pages 6-9, barba2023modelingsarcoglycanopathyin pages 1-2)
Hamster: naturally occurring δ-SG deficiency is particularly useful for cardiomyopathy and systemic therapy studies.
Cellular systems: patient myoblasts, engineered myotubes, and heterologous expression systems are used for trafficking, ERAD, proteasome rescue, splice assays, and AAV construct validation. Mature human iPSC-derived skeletal-muscle/cardiac models and organoids are promising but not yet standardized diagnostic platforms.

The principal model limitation is that disease tempo, immune response to AAV, body size, and cardiac penetrance differ from humans. Consequently, successful rescue in rodents or fish is necessary but not sufficient evidence of clinical efficacy.

Evidence appraisal and principal gaps

The strongest evidence is human cohort evidence for natural history and a 2024 peer-reviewed first-in-human SGCB trial. Mechanistic evidence is mainly model-organism and in vitro evidence. Major unresolved areas include precise population incidence, standardized quality-of-life utilities, validated circulating biomarkers beyond CK, human modifier genes, disease-specific single-cell/multi-omics maps, optimal exercise prescriptions, long-term AAV durability and safety, and therapies for patients with advanced fibrofatty replacement. The most authoritative current interpretation is therefore that sarcoglycanopathy is molecularly well defined but clinically heterogeneous, and that early genotype confirmation plus lifelong cardiac and respiratory surveillance remains essential while gene-replacement efficacy is being confirmed.

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(mendell2024genetherapywith pages 3-4): Jerry R. Mendell, Eric R. Pozsgai, Sarah Lewis, Danielle A. Griffin, Linda P. Lowes, Lindsay N. Alfano, Kelly J. Lehman, Kathleen Church, Natalie F. Reash, Megan A. Iammarino, Brenna Sabo, Rachael Potter, Sarah Neuhaus, Xiaoxi Li, Herb Stevenson, and Louise R. Rodino-Klapac. Gene therapy with bidridistrogene xeboparvovec for limb-girdle muscular dystrophy type 2e/r4: phase 1/2 trial results. Nature Medicine, 30:199-206, Jan 2024. URL: https://doi.org/10.1038/s41591-023-02730-9, doi:10.1038/s41591-023-02730-9. This article has 33 citations and is from a highest quality peer-reviewed journal.
(mendell2024genetherapywith pages 4-5): Jerry R. Mendell, Eric R. Pozsgai, Sarah Lewis, Danielle A. Griffin, Linda P. Lowes, Lindsay N. Alfano, Kelly J. Lehman, Kathleen Church, Natalie F. Reash, Megan A. Iammarino, Brenna Sabo, Rachael Potter, Sarah Neuhaus, Xiaoxi Li, Herb Stevenson, and Louise R. Rodino-Klapac. Gene therapy with bidridistrogene xeboparvovec for limb-girdle muscular dystrophy type 2e/r4: phase 1/2 trial results. Nature Medicine, 30:199-206, Jan 2024. URL: https://doi.org/10.1038/s41591-023-02730-9, doi:10.1038/s41591-023-02730-9. This article has 33 citations and is from a highest quality peer-reviewed journal.
(mendell2024genetherapywith pages 9-10): Jerry R. Mendell, Eric R. Pozsgai, Sarah Lewis, Danielle A. Griffin, Linda P. Lowes, Lindsay N. Alfano, Kelly J. Lehman, Kathleen Church, Natalie F. Reash, Megan A. Iammarino, Brenna Sabo, Rachael Potter, Sarah Neuhaus, Xiaoxi Li, Herb Stevenson, and Louise R. Rodino-Klapac. Gene therapy with bidridistrogene xeboparvovec for limb-girdle muscular dystrophy type 2e/r4: phase 1/2 trial results. Nature Medicine, 30:199-206, Jan 2024. URL: https://doi.org/10.1038/s41591-023-02730-9, doi:10.1038/s41591-023-02730-9. This article has 33 citations and is from a highest quality peer-reviewed journal.
(NCT05973630 chunk 1): ATA-200 Gene Therapy Trial in Patients With LGMDR5. Atamyo Therapeutics. 2025. ClinicalTrials.gov Identifier: NCT05973630

Artifacts

Edison artifact artifact-00

Reference Validation

Checked with linkml-reference-validator 0.2.1.

Outcome	Count
References checked	6
Resolved	6
Unresolved (possible confabulation)	0
Unverifiable	0
References weighed for topical relevance	6
On topic	5
Off topic	0

All extracted references resolved successfully.

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Inheritance

Subtypes

Discussions and Knowledge Gaps

Pathophysiology

Histopathology

Pathograph

Phenotypes

Genetic Associations

Medical Actions

Diagnosis

Prevalence

Clinical Trials

Animal Models

Source YAML

References & Deep Research

References

Deep Research

Disease Characteristics Research Template

Target Disease

Research Objectives

1. Disease Information

2. Etiology

3. Phenotypes

4. Genetic/Molecular Information

5. Environmental Information

6. Mechanism / Pathophysiology

7. Anatomical Structures Affected

8. Temporal Development

9. Inheritance and Population

10. Diagnostics

11. Outcome/Prognosis

12. Treatment

13. Prevention

14. Other Species / Natural Disease

15. Model Organisms

Citation Requirements

Output Format

Sarcoglycanopathy: comprehensive disease-characteristics report

Executive summary

1. Disease information

Definition and identifiers

2. Etiology, risk, protection, and gene–environment interaction

Causal factors

Risk factors

3. Phenotypes

Core phenotype and suggested HPO annotations

Quality of life

4. Genetic and molecular information

5. Environmental, lifestyle, and infectious information

6. Mechanism and pathophysiology

Causal chain

7. Anatomical structures affected

8. Temporal development

9. Inheritance and population

10. Diagnostics

Recommended approach

11. Outcome and prognosis

12. Treatment and current applications

Present standard of care

Pharmacotherapy

Gene and molecular therapy

13. Prevention

14. Other species and natural disease

15. Model organisms and experimental systems

Evidence appraisal and principal gaps

Artifacts

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