Hypotonia-cystinuria syndrome

Mendelian MONDO:0011669 Pathograph 29 contiguous gene deletion syndrome inborn disorder of amino acid transport neurodevelopmental disorder

Hypotonia-cystinuria syndrome is a rare autosomal recessive contiguous-gene deletion disorder of chromosome 2p21. Classic disease involves biallelic loss of SLC3A1 and PREPL, combining type A cystinuria with congenital hypotonia, feeding and growth problems, variable developmental or neurobehavioral features, and risk of cystine nephrolithiasis.

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1
Definitions
1
Inheritance
7
Pathophys.
14
Phenotypes
29
Pathograph
2
Genes
5
Treatments
1
Trials
11
References
1
Deep Research
📘

Definitions

1
Hypotonia-cystinuria syndrome definition
A syndromic form of type A cystinuria in which 2p21 deletions involving SLC3A1 and PREPL cause cystinuria together with neonatal hypotonia and growth or feeding problems.
OTHER
Show evidence (1 reference)
PMID:22766003 SUPPORT Human Clinical
"patients homozygous for these deletions suffer from a general neonatal hypotonia and growth retardation in addition to cystinuria."
This defines the syndromic combination of cystinuria, neonatal hypotonia, and growth impairment in 2p21 deletion patients.
👪

Inheritance

1
Autosomal recessive inheritance HP:0000007
Hypotonia-cystinuria syndrome is usually caused by biallelic, often homozygous or compound heterozygous, deletions affecting SLC3A1 and PREPL.
Autosomal recessive inheritance
Show evidence (1 reference)
PMID:22796000 SUPPORT Human Clinical
"Hypotonia-cystinuria syndrome (HCS) is an autosomal recessive disorder caused by combined deletions of SLC3A1 and PREPL."
This directly states the inheritance and genetic lesion for HCS.
⚙

Pathophysiology

7
SLC3A1-PREPL contiguous gene deletion
Biallelic deletion of adjacent SLC3A1 and PREPL sequences on chromosome 2p21 is the upstream lesion that couples type A cystinuria with the neuromuscular, feeding, and growth phenotype.
SLC3A1 link PREPL link
Downstream
Proximal tubular cystine transport defect Loss of SLC3A1 impairs renal cystine and dibasic amino acid reabsorption.
PREPL-related neuromuscular transmission defect Loss of PREPL contributes to congenital hypotonia, weakness, ptosis, and feeding problems.
PREPL-related growth and appetite dysregulation PREPL loss contributes to growth hormone deficiency, early poor growth, and later hyperphagia or obesity.
Variable developmental and dysmorphic involvement The contiguous deletion presentation includes variable developmental, neurobehavioral, and dysmorphic features.
Show evidence (2 references)
PMID:16385448 SUPPORT Human Clinical
"microdeletion of part of the SLC3A1 and PREPL genes on chromosome 2p21 was found."
The founding cohort directly identifies the contiguous SLC3A1/PREPL deletion.
PMID:34612606 SUPPORT Human Clinical
"Whole exome sequencing (WES), however, revealed a homozygous 2p21 deletion involving two contiquous genes, SLC3A1 (deletion of exons 2-10) and PREPL (deletion of exons 2-14)."
This later sibling report confirms exon-level SLC3A1/PREPL deletion as the molecular diagnosis.
Proximal tubular cystine transport defect
Loss of the SLC3A1-encoded rBAT heavy subunit disrupts proximal tubular and intestinal cystine and dibasic amino acid transport, causing increased urinary cystine and cystine stone risk.
renal proximal tubular epithelial cell link
SLC3A1 link
L-cystine transport link ↓ DECREASED cystine and dibasic amino acid transmembrane transport link ↓ DECREASED
amino acid transmembrane transporter activity link ↓ DECREASED
Downstream
Urinary cystine supersaturation High urinary cystine concentration promotes crystallization and nephrolithiasis.
Cystinuria Defective cystine and dibasic amino-acid reabsorption produces the diagnostic cystinuria phenotype.
Elevated urinary cystine Urinary amino-acid testing detects increased cystine from failed proximal tubular reabsorption.
Show evidence (2 references)
PMID:22480232 SUPPORT Human Clinical
"SLC3A1 (chromosome 2p21) encodes the heavy subunit rBAT of a renal b(0,+) transporter"
This supports the SLC3A1 transporter role in renal cystine handling.
PMID:31024870 SUPPORT Human Clinical
"Both genes are expressed in the renal proximal tubule and in the intestine and encode for different subunits of the transporter of dibasic amino acids (cystine, ornithine, lysine, and arginine)"
This links the affected transporter system to proximal tubular and intestinal amino acid transport.
Urinary cystine supersaturation
Increased urinary cystine concentration can exceed solubility, forming cystine crystals and stones that may obstruct the urinary tract.
Downstream
Cystine nephrolithiasis Cystine stones produce renal and urinary tract morbidity.
Show evidence (1 reference)
PMID:31024870 SUPPORT Human Clinical
"Such transporters deficiency leads to an accumulation of cystine in the urinary tract and to subsequent recurrent stones production, which can eventually lead to end stage renal disease."
This supports the causal step from transporter deficiency to cystine accumulation and recurrent stone formation.
Cystine nephrolithiasis
Cystine stones may occur later than the initial hypotonia presentation, so biochemical cystinuria can precede clinically apparent nephrolithiasis.
Downstream
Nephrolithiasis Clinically apparent cystine stones manifest as nephrolithiasis.
Show evidence (1 reference)
PMID:31024870 SUPPORT Human Clinical
"The diagnosis of HCS can be difficult because neurological signs are aspecific and kidney stones are commonly absent during the first months of life."
This explains why renal stone disease may not be present early despite the underlying cystinuria.
Variable developmental and dysmorphic involvement
HCS has variable developmental, cognitive or neurobehavioral involvement, and minor dysmorphic features, but the intermediate mechanisms connecting the 2p21 deletion to these features remain unresolved.
Downstream
Global developmental delay Variable neurodevelopmental involvement can include global developmental delay.
Minor facial dysmorphism Minor facial dysmorphism is a reported HCS feature without a resolved intermediate mechanism.
Show evidence (2 references)
PMID:22796000 SUPPORT Human Clinical
"Clinical features include cystinuria, neonatal hypotonia with spontaneous improvement, poor feeding in neonates, hyperphagia in childhood, growth hormone deficiency, and variable cognitive problems."
This supports variable cognitive involvement in HCS.
PMID:16385448 SUPPORT Human Clinical
"Patients present with generalized hypotonia at birth, nephrolithiasis, growth hormone deficiency, minor facial dysmorphism, and failure to thrive"
The founding paper lists minor facial dysmorphism among presenting features.
⬡

Pathograph

Use the checkboxes to hide or show graph categories. Hover nodes for evidence and cross-linked metadata.
Pathograph: causal mechanism network for Hypotonia-cystinuria syndrome Interactive directed graph showing how pathophysiology mechanisms, phenotypes, genetic factors and variants, experimental models, environmental triggers, and treatments relate through causal and linked edges.
●

Phenotypes

14
Digestive 1
Feeding difficulties Feeding difficulties (HP:0011968)
Show evidence (1 reference)
PMID:22796000 SUPPORT Human Clinical
"Clinical features include cystinuria, neonatal hypotonia with spontaneous improvement, poor feeding in neonates, hyperphagia in childhood, growth hormone deficiency, and variable cognitive problems."
This directly documents poor feeding in neonates with HCS.
Eye 1
Ptosis Ptosis (HP:0000508)
Show evidence (1 reference)
PMID:24610330 SUPPORT Human Clinical
"The major clinical features of HCS are type A cystinuria, growth hormone deficiency, muscle weakness, ptosis, and feeding problems."
This directly lists ptosis as a major clinical feature of HCS.
Genitourinary 1
Nephrolithiasis Nephrolithiasis (HP:0000787)
Show evidence (2 references)
PMID:31024870 SUPPORT Human Clinical
"After 3 months, a percutaneous nephrolithotripsy was performed to treat the staghorn stone"
This HCS case directly documents clinically significant cystine stone disease requiring intervention.
PMID:34612606 SUPPORT Human Clinical
"Later in childhood, the brother developed cystinuria and nephrolithiasis whereas the older sister suffered from cystinuria and chronic neurobehavioral disturbances."
This sibling report supports later childhood nephrolithiasis and variable expression.
Head and Neck 2
Minor facial dysmorphism Abnormal facial shape (HP:0001999)
Show evidence (1 reference)
PMID:16385448 PARTIAL Human Clinical
"Patients present with generalized hypotonia at birth, nephrolithiasis, growth hormone deficiency, minor facial dysmorphism, and failure to thrive"
The article reports minor facial dysmorphism; HP:0001999 is used as a broad non-coarse facial-shape binding.
Xerostomia Xerostomia (HP:0000217)
Show evidence (1 reference)
PMID:28726805 SUPPORT Human Clinical
"PREPL deficiency causes neonatal hypotonia, ptosis, neonatal feeding difficulties, childhood obesity, xerostomia, and growth hormone deficiency."
The PREPL deficiency delineation paper explicitly lists xerostomia among PREPL-associated phenotypes.
Musculoskeletal 2
Generalized hypotonia VERY_FREQUENT Generalized hypotonia (HP:0001290)
Show evidence (1 reference)
PMID:16385448 SUPPORT Human Clinical
"Patients present with generalized hypotonia at birth, nephrolithiasis, growth hormone deficiency, minor facial dysmorphism, and failure to thrive"
The founding cohort lists generalized hypotonia at birth as a presenting feature.
Muscle weakness Muscle weakness (HP:0001324)
Show evidence (1 reference)
PMID:24610330 SUPPORT Human Clinical
"The major clinical features of HCS are type A cystinuria, growth hormone deficiency, muscle weakness, ptosis, and feeding problems."
This directly lists muscle weakness as a major clinical feature of HCS.
Nervous System 2
Hyperphagia Polyphagia (HP:0002591)
Show evidence (2 references)
PMID:22796000 SUPPORT Human Clinical
"Clinical features include cystinuria, neonatal hypotonia with spontaneous improvement, poor feeding in neonates, hyperphagia in childhood, growth hormone deficiency, and variable cognitive problems."
This directly documents childhood hyperphagia in the HCS clinical feature list.
PMID:16385448 SUPPORT Human Clinical
"and failure to thrive, followed by hyperphagia and rapid weight gain in late childhood."
This supports the temporal pattern of early failure to thrive followed by late-childhood hyperphagia and weight gain.
Global developmental delay OCCASIONAL Global developmental delay (HP:0001263)
Show evidence (1 reference)
PMID:31024870 SUPPORT Human Clinical
"A global developmental delay of all the motor and social skills and of the speech was also evident."
This HCS case documents global developmental delay.
Growth 3
Failure to thrive Failure to thrive (HP:0001508)
Show evidence (1 reference)
PMID:34612606 SUPPORT Human Clinical
"Two siblings presented similarly with congenital hypotonia, lactic acidosis, and failure to thrive."
This directly documents failure to thrive in HCS siblings.
Childhood obesity Obesity (HP:0001513)
Show evidence (1 reference)
PMID:28726805 SUPPORT Human Clinical
"PREPL deficiency causes neonatal hypotonia, ptosis, neonatal feeding difficulties, childhood obesity, xerostomia, and growth hormone deficiency."
The PREPL deficiency delineation paper explicitly lists childhood obesity among PREPL-associated phenotypes, including HCS subjects.
Short stature Short stature (HP:0004322)
Show evidence (1 reference)
PMID:22766003 SUPPORT Human Clinical
"patients homozygous for these deletions suffer from a general neonatal hypotonia and growth retardation in addition to cystinuria."
Growth retardation is a documented feature of HCS.
Other 2
Cystinuria VERY_FREQUENT Cystinuria (HP:0003131)
Show evidence (1 reference)
PMID:22796000 SUPPORT Human Clinical
"Clinical features include cystinuria, neonatal hypotonia with spontaneous improvement, poor feeding in neonates, hyperphagia in childhood, growth hormone deficiency, and variable cognitive problems."
This directly documents cystinuria as part of the HCS clinical feature set.
Growth hormone deficiency Reduced circulating growth hormone concentration (HP:0034323)
Show evidence (1 reference)
PMID:24610330 SUPPORT Human Clinical
"The major clinical features of HCS are type A cystinuria, growth hormone deficiency, muscle weakness, ptosis, and feeding problems."
This directly identifies growth hormone deficiency as a major HCS feature.
🧬

Genetic Associations

2
SLC3A1 (Causal deletion)
Show evidence (1 reference)
PMID:22480232 SUPPORT Human Clinical
"SLC3A1 (chromosome 2p21) encodes the heavy subunit rBAT of a renal b(0,+) transporter"
This supports the functional consequence of SLC3A1 deletion.
PREPL (Causal deletion)
Show evidence (1 reference)
PMID:16385448 SUPPORT Human Clinical
"the extended phenotype can be attributed to the deletion of PREPL."
This directly attributes the non-cystinuria syndromic phenotype to PREPL deletion.
💊

Treatments

5
Human growth hormone replacement therapy
Action: human growth hormone replacement therapy MAXO:0000780
Recombinant human growth hormone therapy can be considered for the PREPL-related growth retardation and growth hormone deficiency component.
Mechanism Target:
MODULATES PREPL-related growth and appetite dysregulation — Replacement therapy addresses the growth hormone deficiency component of the PREPL-related growth phenotype.
Show evidence (1 reference)
PMID:21222627 SUPPORT Other
"Growth retardation is usually observed, which responds well to growth hormone therapy."
The review summarizes observed response of PREPL-associated growth retardation to growth hormone therapy.
Target Phenotypes: Growth hormone deficiency ↗ Short stature ↗
Show evidence (1 reference)
PMID:21222627 SUPPORT Other
"Growth retardation is usually observed, which responds well to growth hormone therapy."
The review directly supports growth hormone therapy responsiveness in PREPL deficiency.
Cystine stone prevention with hydration and diet
Action: dietary intervention MAXO:0000088
High fluid intake and dietary measures reduce cystine concentration and are first-line prevention for the cystinuria component.
Mechanism Target:
INHIBITS Urinary cystine supersaturation — Increased urine volume and dietary measures reduce urinary cystine supersaturation.
Show evidence (1 reference)
PMID:32066273 SUPPORT Human Clinical
"beginning with conservative measures: fluid intake and dietary modification."
This consensus statement supports fluid intake and dietary modification as first-line cystinuria stone-prevention measures.
Urinary alkalinization with potassium citrate
Action: Pharmacotherapy NCIT:C15986
Agent: potassium citrate ↗
Potassium citrate can be used to alkalinize urine and reduce cystine stone recurrence risk in the cystinuria component of HCS.
Mechanism Target:
INHIBITS Urinary cystine supersaturation — Alkalinization improves cystine solubility and helps prevent cystine stones.
Show evidence (2 references)
PMID:32066273 SUPPORT Human Clinical
"proceed to pharmacotherapeutic options by first alkalinizing the urine and then using cystine-binding thiol drugs."
This consensus statement supports urinary alkalinization before cystine-binding thiol therapy.
PMID:31024870 SUPPORT Human Clinical
"Tiopronin (15 mg/kg/day) was immediately started, along with Potassium Citrate."
This HCS case documents potassium citrate use after biochemical cystinuria diagnosis.
Tiopronin therapy
Action: Pharmacotherapy NCIT:C15986
Agent: tiopronin ↗
Tiopronin is a cystine-binding pharmacologic therapy used for cystinuria and was used in a reported HCS case after cystinuria diagnosis.
Mechanism Target:
INHIBITS Urinary cystine supersaturation — Tiopronin lowers cystine stone risk by forming more soluble cysteine-drug complexes.
Show evidence (2 references)
PMID:32066273 SUPPORT Human Clinical
"then using cystine-binding thiol drugs."
This consensus statement supports cystine-binding thiol drugs for recurrent stone formation after conservative measures and alkalinization.
PMID:31024870 SUPPORT Human Clinical
"Tiopronin (15 mg/kg/day) was immediately started, along with Potassium Citrate."
This HCS case documents tiopronin use after biochemical cystinuria diagnosis.
Pyridostigmine trial for PREPL-related myasthenic symptoms
Action: Pharmacotherapy NCIT:C15986
Agent: pyridostigmine ↗
Pyridostigmine may transiently improve PREPL-related myasthenic symptoms in early life, but reported response in HCS was limited and should be treated as partial evidence rather than established disease-modifying therapy.
Mechanism Target:
MODULATES PREPL-related neuromuscular transmission defect — Pyridostigmine may improve neuromuscular transmission symptoms in some PREPL-deficient patients.
Show evidence (1 reference)
PMID:24610330 PARTIAL Human Clinical
"She and 1 of 3 patients with HCS responded transiently to pyridostigmine during infancy."
Response was transient and only observed in one of three HCS patients, so support is partial.
🔬

Biochemical Markers

1
Elevated urinary cystine (INCREASED)
Context: Urinary cystine is increased due to impaired proximal tubular reabsorption.
Pathograph Readouts
Readout Of Proximal tubular cystine transport defect Positive Diagnostic
Elevated urinary cystine reports failed proximal tubular cystine reabsorption.
Show evidence (1 reference)
PMID:31024870 SUPPORT Human Clinical
"The diagnosis of cystinuria was confirmed by urinary amino acid examination (cystine/creatinine 676 mMol/mol, normal value 4–15)."
The urinary amino-acid result provides a diagnostic readout of the SLC3A1 transport defect.
Readout Of Urinary cystine supersaturation Positive Diagnostic
Markedly elevated urinary cystine is the biochemical basis for cystine supersaturation and stone risk.
Show evidence (1 reference)
PMID:31024870 SUPPORT Human Clinical
"Such transporters deficiency leads to an accumulation of cystine in the urinary tract and to subsequent recurrent stones production, which can eventually lead to end stage renal disease."
The report links cystine accumulation in the urinary tract to recurrent stone production.
Show evidence (1 reference)
PMID:31024870 SUPPORT Human Clinical
"The diagnosis of cystinuria was confirmed by urinary amino acid examination (cystine/creatinine 676 mMol/mol, normal value 4–15)."
This directly documents markedly elevated urinary cystine in an HCS case.
🔬

Clinical Trials

1
NCT02640443 PHASE_II UNKNOWN
Phase 2 trial evaluating oral sulfamethoxazole for symptoms of primary PREPL deficiency, including hypotonia-cystinuria syndrome and isolated PREPL deficiency.
Target Phenotypes: Generalized hypotonia ↗ Ptosis ↗ Muscle weakness ↗
Show evidence (1 reference)
clinicaltrials:NCT02640443 SUPPORT Human Clinical
"The investigators will evaluate whether sulfamethoxazole, a sulfamide antibiotic, improves the symptoms of primary PREPL deficiency (hypotonia-cystinuria syndrome and isolated PREPL deficiency)."
The ClinicalTrials.gov record directly identifies the investigational PREPL deficiency therapy and includes HCS.
{ }

Source YAML

click to show 
name: Hypotonia-cystinuria syndrome
creation_date: "2026-05-08T16:18:38Z"
updated_date: "2026-05-21T09:44:51Z"
synonyms:
- HCS
- Hypotonia-cystinuria 2p21 deletion syndrome
- Cystinuria with mitochondrial disease
description: >
  Hypotonia-cystinuria syndrome is a rare autosomal recessive contiguous-gene
  deletion disorder of chromosome 2p21. Classic disease involves biallelic loss
  of SLC3A1 and PREPL, combining type A cystinuria with congenital hypotonia,
  feeding and growth problems, variable developmental or neurobehavioral
  features, and risk of cystine nephrolithiasis.
category: Mendelian
parents:
- contiguous gene deletion syndrome
- inborn disorder of amino acid transport
- neurodevelopmental disorder
disease_term:
  preferred_term: hypotonia-cystinuria syndrome
  term:
    id: MONDO:0011669
    label: hypotonia-cystinuria syndrome
references:
- reference: PMID:16385448
  title: Deletion of PREPL, a gene encoding a putative serine oligopeptidase, in patients with hypotonia-cystinuria syndrome.
  found_in:
  - Hypotonia-Cystinuria_Syndrome-deep-research-falcon.md
- reference: PMID:22766003
  title: 2p21 Deletions in hypotonia-cystinuria syndrome.
  found_in:
  - Hypotonia-Cystinuria_Syndrome-deep-research-falcon.md
- reference: PMID:22796000
  title: Two novel deletions in hypotonia-cystinuria syndrome.
  found_in:
  - Hypotonia-Cystinuria_Syndrome-deep-research-falcon.md
- reference: PMID:34612606
  title: "Hypotonia-cystinuria 2p21 deletion syndrome: Intrafamilial variability of clinical expression."
  found_in:
  - Hypotonia-Cystinuria_Syndrome-deep-research-falcon.md
- reference: PMID:31024870
  title: A Case of Hypotonia-Cystinuria Syndrome With Genito-Urinary Malformations and Extrarenal Involvement.
  found_in:
  - Hypotonia-Cystinuria_Syndrome-deep-research-falcon.md
- reference: PMID:24610330
  title: PREPL deficiency with or without cystinuria causes a novel myasthenic syndrome.
  found_in:
  - Hypotonia-Cystinuria_Syndrome-deep-research-falcon.md
- reference: PMID:28726805
  title: "PREPL deficiency: delineation of the phenotype and development of a functional blood assay."
  found_in:
  - Hypotonia-Cystinuria_Syndrome-deep-research-falcon.md
- reference: PMID:21222627
  title: "PREPL, a prolyl endopeptidase-like enzyme by name only?--Lessons from patients."
  found_in:
  - Hypotonia-Cystinuria_Syndrome-deep-research-falcon.md
- reference: PMID:22480232
  title: "Cystinuria: an inborn cause of urolithiasis."
  found_in:
  - Hypotonia-Cystinuria_Syndrome-deep-research-falcon.md
- reference: PMID:32066273
  title: "Evaluation and Medical Management of Patients with Cystine Nephrolithiasis: A Consensus Statement."
  found_in:
  - Hypotonia-Cystinuria_Syndrome-deep-research-falcon.md
- reference: clinicaltrials:NCT02640443
  title: "Sulfamethoxazole for the Treatment of Primary PREPL Deficiency (In Dutch: Sulfamethoxazole Ter Behandeling Van Primaire PREPL deficiëntie)"
  found_in:
  - Hypotonia-Cystinuria_Syndrome-deep-research-falcon.md
definitions:
- name: Hypotonia-cystinuria syndrome definition
  definition_type: OTHER
  description: >
    A syndromic form of type A cystinuria in which 2p21 deletions involving
    SLC3A1 and PREPL cause cystinuria together with neonatal hypotonia and growth
    or feeding problems.
  evidence:
  - reference: PMID:22766003
    reference_title: 2p21 Deletions in hypotonia-cystinuria syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "patients homozygous for these deletions suffer from a general neonatal hypotonia and growth retardation in addition to cystinuria."
    explanation: This defines the syndromic combination of cystinuria, neonatal hypotonia, and growth impairment in 2p21 deletion patients.
inheritance:
- name: Autosomal recessive inheritance
  description: >
    Hypotonia-cystinuria syndrome is usually caused by biallelic, often
    homozygous or compound heterozygous, deletions affecting SLC3A1 and PREPL.
  inheritance_term:
    preferred_term: Autosomal recessive inheritance
    term:
      id: HP:0000007
      label: Autosomal recessive inheritance
  evidence:
  - reference: PMID:22796000
    reference_title: Two novel deletions in hypotonia-cystinuria syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Hypotonia-cystinuria syndrome (HCS) is an autosomal recessive disorder caused by combined deletions of SLC3A1 and PREPL."
    explanation: This directly states the inheritance and genetic lesion for HCS.
pathophysiology:
- name: SLC3A1-PREPL contiguous gene deletion
  description: >
    Biallelic deletion of adjacent SLC3A1 and PREPL sequences on chromosome 2p21
    is the upstream lesion that couples type A cystinuria with the
    neuromuscular, feeding, and growth phenotype.
  genes:
  - preferred_term: SLC3A1
    term:
      id: hgnc:11025
      label: SLC3A1
  - preferred_term: PREPL
    term:
      id: hgnc:30228
      label: PREPL
  evidence:
  - reference: PMID:16385448
    reference_title: Deletion of PREPL, a gene encoding a putative serine oligopeptidase, in patients with hypotonia-cystinuria syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "microdeletion of part of the SLC3A1 and PREPL genes on chromosome 2p21 was found."
    explanation: The founding cohort directly identifies the contiguous SLC3A1/PREPL deletion.
  - reference: PMID:34612606
    reference_title: "Hypotonia-cystinuria 2p21 deletion syndrome: Intrafamilial variability of clinical expression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Whole exome sequencing (WES), however, revealed a homozygous 2p21 deletion involving two contiquous genes, SLC3A1 (deletion of exons 2-10) and PREPL (deletion of exons 2-14)."
    explanation: This later sibling report confirms exon-level SLC3A1/PREPL deletion as the molecular diagnosis.
  downstream:
  - target: Proximal tubular cystine transport defect
    description: Loss of SLC3A1 impairs renal cystine and dibasic amino acid reabsorption.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:16385448
      reference_title: Deletion of PREPL, a gene encoding a putative serine oligopeptidase, in patients with hypotonia-cystinuria syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "microdeletion of part of the SLC3A1 and PREPL genes on chromosome 2p21 was found."
      explanation: The deleted SLC3A1 component explains the type A cystinuria transport defect.
  - target: PREPL-related neuromuscular transmission defect
    description: Loss of PREPL contributes to congenital hypotonia, weakness, ptosis, and feeding problems.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:16385448
      reference_title: Deletion of PREPL, a gene encoding a putative serine oligopeptidase, in patients with hypotonia-cystinuria syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "the extended phenotype can be attributed to the deletion of PREPL."
      explanation: The founding paper attributes the non-cystinuria syndromic phenotype to PREPL loss.
  - target: PREPL-related growth and appetite dysregulation
    description: PREPL loss contributes to growth hormone deficiency, early poor growth, and later hyperphagia or obesity.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - growth hormone deficiency
    - neonatal feeding difficulty
    evidence:
    - reference: PMID:28726805
      reference_title: "PREPL deficiency: delineation of the phenotype and development of a functional blood assay."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "PREPL deficiency causes neonatal hypotonia, ptosis, neonatal feeding difficulties, childhood obesity, xerostomia, and growth hormone deficiency."
      explanation: PREPL deficiency directly supports a growth, feeding, obesity, and xerostomia branch in HCS.
  - target: Variable developmental and dysmorphic involvement
    description: The contiguous deletion presentation includes variable developmental, neurobehavioral, and dysmorphic features.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:22796000
      reference_title: Two novel deletions in hypotonia-cystinuria syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Clinical features include cystinuria, neonatal hypotonia with spontaneous improvement, poor feeding in neonates, hyperphagia in childhood, growth hormone deficiency, and variable cognitive problems."
      explanation: HCS case literature supports variable neurodevelopmental involvement beyond the renal and neuromuscular branches.
- name: Proximal tubular cystine transport defect
  description: >
    Loss of the SLC3A1-encoded rBAT heavy subunit disrupts proximal tubular and
    intestinal cystine and dibasic amino acid transport, causing increased
    urinary cystine and cystine stone risk.
  genes:
  - preferred_term: SLC3A1
    term:
      id: hgnc:11025
      label: SLC3A1
  cell_types:
  - preferred_term: renal proximal tubular epithelial cell
    term:
      id: CL:0002306
      label: epithelial cell of proximal tubule
  biological_processes:
  - preferred_term: L-cystine transport
    modifier: DECREASED
    term:
      id: GO:0015811
      label: L-cystine transport
  - preferred_term: cystine and dibasic amino acid transmembrane transport
    modifier: DECREASED
    term:
      id: GO:0003333
      label: amino acid transmembrane transport
  molecular_functions:
  - preferred_term: amino acid transmembrane transporter activity
    modifier: DECREASED
    term:
      id: GO:0015171
      label: amino acid transmembrane transporter activity
  chemical_entities:
  - preferred_term: cystine
    term:
      id: CHEBI:17376
      label: cystine
    modifier: INCREASED
  - preferred_term: L-lysine
    term:
      id: CHEBI:18019
      label: L-lysine
    modifier: INCREASED
  - preferred_term: L-arginine
    term:
      id: CHEBI:16467
      label: L-arginine
    modifier: INCREASED
  - preferred_term: ornithine
    term:
      id: CHEBI:18257
      label: ornithine
    modifier: INCREASED
  evidence:
  - reference: PMID:22480232
    reference_title: "Cystinuria: an inborn cause of urolithiasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "SLC3A1 (chromosome 2p21) encodes the heavy subunit rBAT of a renal b(0,+) transporter"
    explanation: This supports the SLC3A1 transporter role in renal cystine handling.
  - reference: PMID:31024870
    reference_title: A Case of Hypotonia-Cystinuria Syndrome With Genito-Urinary Malformations and Extrarenal Involvement.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Both genes are expressed in the renal proximal tubule and in the intestine and encode for different subunits of the transporter of dibasic amino acids (cystine, ornithine, lysine, and arginine)"
    explanation: This links the affected transporter system to proximal tubular and intestinal amino acid transport.
  downstream:
  - target: Urinary cystine supersaturation
    description: High urinary cystine concentration promotes crystallization and nephrolithiasis.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:31024870
      reference_title: A Case of Hypotonia-Cystinuria Syndrome With Genito-Urinary Malformations and Extrarenal Involvement.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Such transporters deficiency leads to an accumulation of cystine in the urinary tract and to subsequent recurrent stones production, which can eventually lead to end stage renal disease."
      explanation: The HCS case report directly links transporter deficiency to urinary cystine accumulation and stone formation.
  - target: Cystinuria
    description: Defective cystine and dibasic amino-acid reabsorption produces the diagnostic cystinuria phenotype.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:22796000
      reference_title: Two novel deletions in hypotonia-cystinuria syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Clinical features include cystinuria, neonatal hypotonia with spontaneous improvement, poor feeding in neonates, hyperphagia in childhood, growth hormone deficiency, and variable cognitive problems."
      explanation: This HCS report lists cystinuria as a core clinical feature of the transporter-deletion syndrome.
  - target: Elevated urinary cystine
    description: Urinary amino-acid testing detects increased cystine from failed proximal tubular reabsorption.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:31024870
      reference_title: A Case of Hypotonia-Cystinuria Syndrome With Genito-Urinary Malformations and Extrarenal Involvement.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The diagnosis of cystinuria was confirmed by urinary amino acid examination (cystine/creatinine 676 mMol/mol, normal value 4–15)."
      explanation: The biochemical assay documents elevated urinary cystine downstream of the transporter defect.
- name: Urinary cystine supersaturation
  description: >
    Increased urinary cystine concentration can exceed solubility, forming
    cystine crystals and stones that may obstruct the urinary tract.
  chemical_entities:
  - preferred_term: cystine
    term:
      id: CHEBI:17376
      label: cystine
    modifier: INCREASED
  evidence:
  - reference: PMID:31024870
    reference_title: A Case of Hypotonia-Cystinuria Syndrome With Genito-Urinary Malformations and Extrarenal Involvement.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Such transporters deficiency leads to an accumulation of cystine in the urinary tract and to subsequent recurrent stones production, which can eventually lead to end stage renal disease."
    explanation: This supports the causal step from transporter deficiency to cystine accumulation and recurrent stone formation.
  downstream:
  - target: Cystine nephrolithiasis
    description: Cystine stones produce renal and urinary tract morbidity.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:31024870
      reference_title: A Case of Hypotonia-Cystinuria Syndrome With Genito-Urinary Malformations and Extrarenal Involvement.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Such transporters deficiency leads to an accumulation of cystine in the urinary tract and to subsequent recurrent stones production, which can eventually lead to end stage renal disease."
      explanation: The HCS case report connects urinary cystine accumulation with recurrent stone production.
- name: PREPL-related neuromuscular transmission defect
  description: >
    PREPL loss causes a congenital myasthenic syndrome with impaired
    neuromuscular transmission, explaining hypotonia, weakness, ptosis, and
    neonatal feeding problems in HCS and isolated PREPL deficiency.
  genes:
  - preferred_term: PREPL
    term:
      id: hgnc:30228
      label: PREPL
  cell_types:
  - preferred_term: motor neuron
    term:
      id: CL:0000100
      label: motor neuron
  biological_processes:
  - preferred_term: synaptic vesicle exocytosis
    modifier: DECREASED
    term:
      id: GO:0016079
      label: synaptic vesicle exocytosis
  - preferred_term: chemical synaptic transmission
    modifier: DECREASED
    term:
      id: GO:0007268
      label: chemical synaptic transmission
  evidence:
  - reference: PMID:24610330
    reference_title: PREPL deficiency with or without cystinuria causes a novel myasthenic syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The major clinical features of HCS are type A cystinuria, growth hormone deficiency, muscle weakness, ptosis, and feeding problems."
    explanation: This connects PREPL deficiency with the neuromuscular and endocrine phenotype seen in HCS.
  - reference: PMID:24610330
    reference_title: PREPL deficiency with or without cystinuria causes a novel myasthenic syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Isolated PREPL deficiency is a novel monogenic disorder that causes a congenital myasthenic syndrome with pre- and postsynaptic features and growth hormone deficiency."
    explanation: This supports a neuromuscular-transmission mechanism for PREPL-related hypotonia and weakness.
  downstream:
  - target: Generalized hypotonia
    description: Neuromuscular transmission impairment produces early generalized hypotonia.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:24610330
      reference_title: PREPL deficiency with or without cystinuria causes a novel myasthenic syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Isolated PREPL deficiency is a novel monogenic disorder that causes a congenital myasthenic syndrome with pre- and postsynaptic features and growth hormone deficiency."
      explanation: PREPL-related myasthenic transmission defects explain the hypotonia component.
  - target: Feeding difficulties
    description: Bulbar or generalized weakness can impair neonatal feeding.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:24610330
      reference_title: PREPL deficiency with or without cystinuria causes a novel myasthenic syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The major clinical features of HCS are type A cystinuria, growth hormone deficiency, muscle weakness, ptosis, and feeding problems."
      explanation: Feeding problems are listed among the major PREPL/HCS clinical features.
  - target: Muscle weakness
    description: PREPL-related myasthenic transmission impairment produces muscle weakness.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:24610330
      reference_title: PREPL deficiency with or without cystinuria causes a novel myasthenic syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The major clinical features of HCS are type A cystinuria, growth hormone deficiency, muscle weakness, ptosis, and feeding problems."
      explanation: The PREPL deficiency paper directly lists muscle weakness as a major HCS feature.
  - target: Ptosis
    description: Ocular muscle involvement in the PREPL-related myasthenic syndrome produces ptosis.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:24610330
      reference_title: PREPL deficiency with or without cystinuria causes a novel myasthenic syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The major clinical features of HCS are type A cystinuria, growth hormone deficiency, muscle weakness, ptosis, and feeding problems."
      explanation: Ptosis is listed among the major PREPL/HCS clinical features.
  - target: Growth hormone deficiency
    description: PREPL deficiency is associated with growth hormone deficiency in HCS and isolated PREPL deficiency.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:24610330
      reference_title: PREPL deficiency with or without cystinuria causes a novel myasthenic syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The major clinical features of HCS are type A cystinuria, growth hormone deficiency, muscle weakness, ptosis, and feeding problems."
      explanation: Growth hormone deficiency is a major clinical feature of HCS/PREPL deficiency, although the intermediate mechanism is not resolved.
- name: Cystine nephrolithiasis
  description: >
    Cystine stones may occur later than the initial hypotonia presentation, so
    biochemical cystinuria can precede clinically apparent nephrolithiasis.
  chemical_entities:
  - preferred_term: cystine
    term:
      id: CHEBI:17376
      label: cystine
    modifier: INCREASED
  evidence:
  - reference: PMID:31024870
    reference_title: A Case of Hypotonia-Cystinuria Syndrome With Genito-Urinary Malformations and Extrarenal Involvement.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diagnosis of HCS can be difficult because neurological signs are aspecific and kidney stones are commonly absent during the first months of life."
    explanation: This explains why renal stone disease may not be present early despite the underlying cystinuria.
  downstream:
  - target: Nephrolithiasis
    description: Clinically apparent cystine stones manifest as nephrolithiasis.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:31024870
      reference_title: A Case of Hypotonia-Cystinuria Syndrome With Genito-Urinary Malformations and Extrarenal Involvement.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "After 3 months, a percutaneous nephrolithotripsy was performed to treat the staghorn stone"
      explanation: This HCS case documents clinically significant nephrolithiasis requiring intervention.
- name: PREPL-related growth and appetite dysregulation
  description: >
    PREPL deficiency contributes to growth hormone deficiency, neonatal feeding
    problems, early failure to thrive, and later appetite or weight-gain
    abnormalities including hyperphagia and childhood obesity.
  genes:
  - preferred_term: PREPL
    term:
      id: hgnc:30228
      label: PREPL
  biological_processes:
  - preferred_term: growth hormone secretion
    modifier: DECREASED
    term:
      id: GO:0030252
      label: growth hormone secretion
  evidence:
  - reference: PMID:28726805
    reference_title: "PREPL deficiency: delineation of the phenotype and development of a functional blood assay."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "PREPL deficiency causes neonatal hypotonia, ptosis, neonatal feeding difficulties, childhood obesity, xerostomia, and growth hormone deficiency."
    explanation: The PREPL deficiency delineation paper directly supports the growth, obesity, feeding, xerostomia, and endocrine branch.
  - reference: PMID:16385448
    reference_title: Deletion of PREPL, a gene encoding a putative serine oligopeptidase, in patients with hypotonia-cystinuria syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "and failure to thrive, followed by hyperphagia and rapid weight gain in late childhood."
    explanation: The founding HCS report supports the temporal pattern from early failure to thrive to later hyperphagia and rapid weight gain.
  downstream:
  - target: Failure to thrive
    description: Early feeding and growth impairment manifests as failure to thrive.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:16385448
      reference_title: Deletion of PREPL, a gene encoding a putative serine oligopeptidase, in patients with hypotonia-cystinuria syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "and failure to thrive, followed by hyperphagia and rapid weight gain in late childhood."
      explanation: The HCS report directly supports early failure to thrive in this growth/appetite trajectory.
  - target: Growth hormone deficiency
    description: PREPL deficiency is associated with growth hormone deficiency.
    causal_link_type: DIRECT
    evidence:
    - reference: PMID:28726805
      reference_title: "PREPL deficiency: delineation of the phenotype and development of a functional blood assay."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "PREPL deficiency causes neonatal hypotonia, ptosis, neonatal feeding difficulties, childhood obesity, xerostomia, and growth hormone deficiency."
      explanation: The PREPL deficiency delineation paper lists growth hormone deficiency as part of the phenotype.
  - target: Short stature
    description: Growth retardation and growth hormone deficiency contribute to short stature.
    causal_link_type: INDIRECT_KNOWN_INTERMEDIATES
    intermediate_mechanisms:
    - growth hormone deficiency
    evidence:
    - reference: PMID:22766003
      reference_title: 2p21 Deletions in hypotonia-cystinuria syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "patients homozygous for these deletions suffer from a general neonatal hypotonia and growth retardation in addition to cystinuria."
      explanation: HCS deletion cases have growth retardation in addition to hypotonia and cystinuria.
  - target: Hyperphagia
    description: Later childhood hyperphagia follows the early poor-feeding period in some HCS patients.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:22796000
      reference_title: Two novel deletions in hypotonia-cystinuria syndrome.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Clinical features include cystinuria, neonatal hypotonia with spontaneous improvement, poor feeding in neonates, hyperphagia in childhood, growth hormone deficiency, and variable cognitive problems."
      explanation: HCS clinical features include childhood hyperphagia after neonatal poor feeding.
  - target: Childhood obesity
    description: PREPL deficiency can produce childhood obesity after the early feeding/growth phase.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:28726805
      reference_title: "PREPL deficiency: delineation of the phenotype and development of a functional blood assay."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "PREPL deficiency causes neonatal hypotonia, ptosis, neonatal feeding difficulties, childhood obesity, xerostomia, and growth hormone deficiency."
      explanation: The PREPL deficiency paper directly lists childhood obesity.
  - target: Xerostomia
    description: Xerostomia is part of the broader PREPL deficiency phenotype.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:28726805
      reference_title: "PREPL deficiency: delineation of the phenotype and development of a functional blood assay."
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "PREPL deficiency causes neonatal hypotonia, ptosis, neonatal feeding difficulties, childhood obesity, xerostomia, and growth hormone deficiency."
      explanation: The PREPL deficiency paper directly lists xerostomia.
- name: Variable developmental and dysmorphic involvement
  description: >
    HCS has variable developmental, cognitive or neurobehavioral involvement,
    and minor dysmorphic features, but the intermediate mechanisms connecting
    the 2p21 deletion to these features remain unresolved.
  evidence:
  - reference: PMID:22796000
    reference_title: Two novel deletions in hypotonia-cystinuria syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical features include cystinuria, neonatal hypotonia with spontaneous improvement, poor feeding in neonates, hyperphagia in childhood, growth hormone deficiency, and variable cognitive problems."
    explanation: This supports variable cognitive involvement in HCS.
  - reference: PMID:16385448
    reference_title: Deletion of PREPL, a gene encoding a putative serine oligopeptidase, in patients with hypotonia-cystinuria syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients present with generalized hypotonia at birth, nephrolithiasis, growth hormone deficiency, minor facial dysmorphism, and failure to thrive"
    explanation: The founding paper lists minor facial dysmorphism among presenting features.
  downstream:
  - target: Global developmental delay
    description: Variable neurodevelopmental involvement can include global developmental delay.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:31024870
      reference_title: A Case of Hypotonia-Cystinuria Syndrome With Genito-Urinary Malformations and Extrarenal Involvement.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "A global developmental delay of all the motor and social skills and of the speech was also evident."
      explanation: This HCS case directly documents global developmental delay.
  - target: Minor facial dysmorphism
    description: Minor facial dysmorphism is a reported HCS feature without a resolved intermediate mechanism.
    causal_link_type: INDIRECT_UNKNOWN_INTERMEDIATES
    evidence:
    - reference: PMID:16385448
      reference_title: Deletion of PREPL, a gene encoding a putative serine oligopeptidase, in patients with hypotonia-cystinuria syndrome.
      supports: PARTIAL
      evidence_source: HUMAN_CLINICAL
      snippet: "Patients present with generalized hypotonia at birth, nephrolithiasis, growth hormone deficiency, minor facial dysmorphism, and failure to thrive"
      explanation: The founding paper reports minor facial dysmorphism; the causal intermediate remains unresolved.
phenotypes:
- category: Neurologic
  name: Generalized hypotonia
  description: Generalized neonatal or infantile hypotonia is a defining feature of HCS.
  frequency: VERY_FREQUENT
  diagnostic: true
  phenotype_term:
    preferred_term: Generalized hypotonia
    term:
      id: HP:0001290
      label: Generalized hypotonia
  evidence:
  - reference: PMID:16385448
    reference_title: Deletion of PREPL, a gene encoding a putative serine oligopeptidase, in patients with hypotonia-cystinuria syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients present with generalized hypotonia at birth, nephrolithiasis, growth hormone deficiency, minor facial dysmorphism, and failure to thrive"
    explanation: The founding cohort lists generalized hypotonia at birth as a presenting feature.
- category: Biochemical
  name: Cystinuria
  description: Increased urinary cystine reflects the SLC3A1-mediated amino acid transport defect.
  frequency: VERY_FREQUENT
  diagnostic: true
  phenotype_term:
    preferred_term: Cystinuria
    term:
      id: HP:0003131
      label: Cystinuria
  evidence:
  - reference: PMID:22796000
    reference_title: Two novel deletions in hypotonia-cystinuria syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical features include cystinuria, neonatal hypotonia with spontaneous improvement, poor feeding in neonates, hyperphagia in childhood, growth hormone deficiency, and variable cognitive problems."
    explanation: This directly documents cystinuria as part of the HCS clinical feature set.
- category: Renal
  name: Nephrolithiasis
  description: Cystine stones may develop from the cystinuria component and can cause obstructive urinary tract morbidity.
  phenotype_term:
    preferred_term: Nephrolithiasis
    term:
      id: HP:0000787
      label: Nephrolithiasis
  evidence:
  - reference: PMID:31024870
    reference_title: A Case of Hypotonia-Cystinuria Syndrome With Genito-Urinary Malformations and Extrarenal Involvement.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "After 3 months, a percutaneous nephrolithotripsy was performed to treat the staghorn stone"
    explanation: This HCS case directly documents clinically significant cystine stone disease requiring intervention.
  - reference: PMID:34612606
    reference_title: "Hypotonia-cystinuria 2p21 deletion syndrome: Intrafamilial variability of clinical expression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Later in childhood, the brother developed cystinuria and nephrolithiasis whereas the older sister suffered from cystinuria and chronic neurobehavioral disturbances."
    explanation: This sibling report supports later childhood nephrolithiasis and variable expression.
- category: Growth
  name: Failure to thrive
  description: Poor early growth and feeding difficulty are common early manifestations.
  phenotype_term:
    preferred_term: Failure to thrive
    term:
      id: HP:0001508
      label: Failure to thrive
  evidence:
  - reference: PMID:34612606
    reference_title: "Hypotonia-cystinuria 2p21 deletion syndrome: Intrafamilial variability of clinical expression."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Two siblings presented similarly with congenital hypotonia, lactic acidosis, and failure to thrive."
    explanation: This directly documents failure to thrive in HCS siblings.
- category: Endocrine
  name: Growth hormone deficiency
  description: Growth hormone deficiency contributes to the short-stature and growth-failure component of HCS.
  phenotype_term:
    preferred_term: Growth hormone deficiency
    term:
      id: HP:0034323
      label: Reduced circulating growth hormone concentration
  evidence:
  - reference: PMID:24610330
    reference_title: PREPL deficiency with or without cystinuria causes a novel myasthenic syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The major clinical features of HCS are type A cystinuria, growth hormone deficiency, muscle weakness, ptosis, and feeding problems."
    explanation: This directly identifies growth hormone deficiency as a major HCS feature.
- category: Neurologic
  name: Muscle weakness
  description: Muscle weakness is part of the PREPL-related neuromuscular phenotype and is distinct from neonatal hypotonia.
  phenotype_term:
    preferred_term: Muscle weakness
    term:
      id: HP:0001324
      label: Muscle weakness
  evidence:
  - reference: PMID:24610330
    reference_title: PREPL deficiency with or without cystinuria causes a novel myasthenic syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The major clinical features of HCS are type A cystinuria, growth hormone deficiency, muscle weakness, ptosis, and feeding problems."
    explanation: This directly lists muscle weakness as a major clinical feature of HCS.
- category: Ophthalmologic
  name: Ptosis
  description: Ptosis is a major PREPL-related neuromuscular feature in HCS and isolated PREPL deficiency.
  phenotype_term:
    preferred_term: Ptosis
    term:
      id: HP:0000508
      label: Ptosis
  evidence:
  - reference: PMID:24610330
    reference_title: PREPL deficiency with or without cystinuria causes a novel myasthenic syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The major clinical features of HCS are type A cystinuria, growth hormone deficiency, muscle weakness, ptosis, and feeding problems."
    explanation: This directly lists ptosis as a major clinical feature of HCS.
- category: Behavioral
  name: Hyperphagia
  description: Hyperphagia can emerge in childhood after early failure to thrive and poor feeding.
  phenotype_term:
    preferred_term: Hyperphagia
    term:
      id: HP:0002591
      label: Polyphagia
  evidence:
  - reference: PMID:22796000
    reference_title: Two novel deletions in hypotonia-cystinuria syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical features include cystinuria, neonatal hypotonia with spontaneous improvement, poor feeding in neonates, hyperphagia in childhood, growth hormone deficiency, and variable cognitive problems."
    explanation: This directly documents childhood hyperphagia in the HCS clinical feature list.
  - reference: PMID:16385448
    reference_title: Deletion of PREPL, a gene encoding a putative serine oligopeptidase, in patients with hypotonia-cystinuria syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "and failure to thrive, followed by hyperphagia and rapid weight gain in late childhood."
    explanation: This supports the temporal pattern of early failure to thrive followed by late-childhood hyperphagia and weight gain.
- category: Endocrine
  name: Childhood obesity
  description: Childhood obesity can emerge after the early failure-to-thrive phase and is a named PREPL deficiency feature.
  phenotype_term:
    preferred_term: Childhood obesity
    term:
      id: HP:0001513
      label: Obesity
  evidence:
  - reference: PMID:28726805
    reference_title: "PREPL deficiency: delineation of the phenotype and development of a functional blood assay."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "PREPL deficiency causes neonatal hypotonia, ptosis, neonatal feeding difficulties, childhood obesity, xerostomia, and growth hormone deficiency."
    explanation: The PREPL deficiency delineation paper explicitly lists childhood obesity among PREPL-associated phenotypes, including HCS subjects.
- category: Growth
  name: Short stature
  description: Growth retardation and short stature are reported in the HCS phenotype.
  phenotype_term:
    preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  evidence:
  - reference: PMID:22766003
    reference_title: 2p21 Deletions in hypotonia-cystinuria syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "patients homozygous for these deletions suffer from a general neonatal hypotonia and growth retardation in addition to cystinuria."
    explanation: Growth retardation is a documented feature of HCS.
- category: Gastrointestinal
  name: Feeding difficulties
  description: Neonatal poor feeding can accompany hypotonia and neuromuscular weakness.
  phenotype_term:
    preferred_term: Feeding difficulties
    term:
      id: HP:0011968
      label: Feeding difficulties
  evidence:
  - reference: PMID:22796000
    reference_title: Two novel deletions in hypotonia-cystinuria syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Clinical features include cystinuria, neonatal hypotonia with spontaneous improvement, poor feeding in neonates, hyperphagia in childhood, growth hormone deficiency, and variable cognitive problems."
    explanation: This directly documents poor feeding in neonates with HCS.
- category: Developmental
  name: Global developmental delay
  description: Developmental delay is variably reported in HCS and related 2p21 deletion presentations.
  frequency: OCCASIONAL
  phenotype_term:
    preferred_term: Global developmental delay
    term:
      id: HP:0001263
      label: Global developmental delay
  evidence:
  - reference: PMID:31024870
    reference_title: A Case of Hypotonia-Cystinuria Syndrome With Genito-Urinary Malformations and Extrarenal Involvement.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "A global developmental delay of all the motor and social skills and of the speech was also evident."
    explanation: This HCS case documents global developmental delay.
- category: Craniofacial
  name: Minor facial dysmorphism
  description: Minor dysmorphic facial features are reported but are not the primary diagnostic feature.
  phenotype_term:
    preferred_term: Minor facial dysmorphism
    term:
      id: HP:0001999
      label: Abnormal facial shape
  evidence:
  - reference: PMID:16385448
    reference_title: Deletion of PREPL, a gene encoding a putative serine oligopeptidase, in patients with hypotonia-cystinuria syndrome.
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "Patients present with generalized hypotonia at birth, nephrolithiasis, growth hormone deficiency, minor facial dysmorphism, and failure to thrive"
    explanation: The article reports minor facial dysmorphism; HP:0001999 is used as a broad non-coarse facial-shape binding.
- category: Oral
  name: Xerostomia
  description: Xerostomia is reported as part of the broader PREPL deficiency phenotype.
  phenotype_term:
    preferred_term: Xerostomia
    term:
      id: HP:0000217
      label: Xerostomia
  evidence:
  - reference: PMID:28726805
    reference_title: "PREPL deficiency: delineation of the phenotype and development of a functional blood assay."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "PREPL deficiency causes neonatal hypotonia, ptosis, neonatal feeding difficulties, childhood obesity, xerostomia, and growth hormone deficiency."
    explanation: The PREPL deficiency delineation paper explicitly lists xerostomia among PREPL-associated phenotypes.
biochemical:
- name: Elevated urinary cystine
  presence: INCREASED
  context: Urinary cystine is increased due to impaired proximal tubular reabsorption.
  biomarker_term:
    preferred_term: cystine
    term:
      id: CHEBI:17376
      label: cystine
  readouts:
  - target: Proximal tubular cystine transport defect
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Elevated urinary cystine reports failed proximal tubular cystine reabsorption.
    evidence:
    - reference: PMID:31024870
      reference_title: A Case of Hypotonia-Cystinuria Syndrome With Genito-Urinary Malformations and Extrarenal Involvement.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "The diagnosis of cystinuria was confirmed by urinary amino acid examination (cystine/creatinine 676 mMol/mol, normal value 4–15)."
      explanation: The urinary amino-acid result provides a diagnostic readout of the SLC3A1 transport defect.
  - target: Urinary cystine supersaturation
    relationship: READOUT_OF
    direction: POSITIVE
    endpoint_context: DIAGNOSTIC
    interpretation: Markedly elevated urinary cystine is the biochemical basis for cystine supersaturation and stone risk.
    evidence:
    - reference: PMID:31024870
      reference_title: A Case of Hypotonia-Cystinuria Syndrome With Genito-Urinary Malformations and Extrarenal Involvement.
      supports: SUPPORT
      evidence_source: HUMAN_CLINICAL
      snippet: "Such transporters deficiency leads to an accumulation of cystine in the urinary tract and to subsequent recurrent stones production, which can eventually lead to end stage renal disease."
      explanation: The report links cystine accumulation in the urinary tract to recurrent stone production.
  evidence:
  - reference: PMID:31024870
    reference_title: A Case of Hypotonia-Cystinuria Syndrome With Genito-Urinary Malformations and Extrarenal Involvement.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The diagnosis of cystinuria was confirmed by urinary amino acid examination (cystine/creatinine 676 mMol/mol, normal value 4–15)."
    explanation: This directly documents markedly elevated urinary cystine in an HCS case.
genetic:
- name: SLC3A1
  association: Causal deletion
  gene_term:
    preferred_term: SLC3A1
    term:
      id: hgnc:11025
      label: SLC3A1
  notes: >
    SLC3A1 deletion causes the type A cystinuria component by disrupting the
    rBAT heavy subunit of the renal b(0,+) cystine/dibasic amino acid transporter.
  evidence:
  - reference: PMID:22480232
    reference_title: "Cystinuria: an inborn cause of urolithiasis."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "SLC3A1 (chromosome 2p21) encodes the heavy subunit rBAT of a renal b(0,+) transporter"
    explanation: This supports the functional consequence of SLC3A1 deletion.
- name: PREPL
  association: Causal deletion
  gene_term:
    preferred_term: PREPL
    term:
      id: hgnc:30228
      label: PREPL
  notes: >
    PREPL deletion causes the neuromuscular and growth phenotype, including
    hypotonia, feeding problems, ptosis or weakness, and growth hormone
    deficiency.
  evidence:
  - reference: PMID:16385448
    reference_title: Deletion of PREPL, a gene encoding a putative serine oligopeptidase, in patients with hypotonia-cystinuria syndrome.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "the extended phenotype can be attributed to the deletion of PREPL."
    explanation: This directly attributes the non-cystinuria syndromic phenotype to PREPL deletion.
treatments:
- name: Human growth hormone replacement therapy
  description: >
    Recombinant human growth hormone therapy can be considered for the PREPL-related
    growth retardation and growth hormone deficiency component.
  treatment_term:
    preferred_term: human growth hormone replacement therapy
    term:
      id: MAXO:0000780
      label: human growth hormone replacement therapy
  target_phenotypes:
  - preferred_term: Growth hormone deficiency
    term:
      id: HP:0034323
      label: Reduced circulating growth hormone concentration
  - preferred_term: Short stature
    term:
      id: HP:0004322
      label: Short stature
  target_mechanisms:
  - target: PREPL-related growth and appetite dysregulation
    treatment_effect: MODULATES
    description: Replacement therapy addresses the growth hormone deficiency component of the PREPL-related growth phenotype.
    evidence:
    - reference: PMID:21222627
      reference_title: "PREPL, a prolyl endopeptidase-like enzyme by name only?--Lessons from patients."
      supports: SUPPORT
      evidence_source: OTHER
      snippet: "Growth retardation is usually observed, which responds well to growth hormone therapy."
      explanation: The review summarizes observed response of PREPL-associated growth retardation to growth hormone therapy.
  evidence:
  - reference: PMID:21222627
    reference_title: "PREPL, a prolyl endopeptidase-like enzyme by name only?--Lessons from patients."
    supports: SUPPORT
    evidence_source: OTHER
    snippet: "Growth retardation is usually observed, which responds well to growth hormone therapy."
    explanation: The review directly supports growth hormone therapy responsiveness in PREPL deficiency.
- name: Cystine stone prevention with hydration and diet
  description: >
    High fluid intake and dietary measures reduce cystine concentration and are
    first-line prevention for the cystinuria component.
  treatment_term:
    preferred_term: dietary intervention
    term:
      id: MAXO:0000088
      label: dietary intervention
  target_mechanisms:
  - target: Urinary cystine supersaturation
    treatment_effect: INHIBITS
    description: Increased urine volume and dietary measures reduce urinary cystine supersaturation.
  evidence:
  - reference: PMID:32066273
    reference_title: "Evaluation and Medical Management of Patients with Cystine Nephrolithiasis: A Consensus Statement."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "beginning with conservative measures: fluid intake and dietary modification."
    explanation: This consensus statement supports fluid intake and dietary modification as first-line cystinuria stone-prevention measures.
- name: Urinary alkalinization with potassium citrate
  description: >
    Potassium citrate can be used to alkalinize urine and reduce cystine stone
    recurrence risk in the cystinuria component of HCS.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: potassium citrate
      term:
        id: CHEBI:64733
        label: potassium citrate (anhydrous)
  target_mechanisms:
  - target: Urinary cystine supersaturation
    treatment_effect: INHIBITS
    description: Alkalinization improves cystine solubility and helps prevent cystine stones.
  evidence:
  - reference: PMID:32066273
    reference_title: "Evaluation and Medical Management of Patients with Cystine Nephrolithiasis: A Consensus Statement."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "proceed to pharmacotherapeutic options by first alkalinizing the urine and then using cystine-binding thiol drugs."
    explanation: This consensus statement supports urinary alkalinization before cystine-binding thiol therapy.
  - reference: PMID:31024870
    reference_title: A Case of Hypotonia-Cystinuria Syndrome With Genito-Urinary Malformations and Extrarenal Involvement.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Tiopronin (15 mg/kg/day) was immediately started, along with Potassium Citrate."
    explanation: This HCS case documents potassium citrate use after biochemical cystinuria diagnosis.
- name: Tiopronin therapy
  description: >
    Tiopronin is a cystine-binding pharmacologic therapy used for cystinuria and
    was used in a reported HCS case after cystinuria diagnosis.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: tiopronin
      term:
        id: NCIT:C47758
        label: Tiopronin
  target_mechanisms:
  - target: Urinary cystine supersaturation
    treatment_effect: INHIBITS
    description: Tiopronin lowers cystine stone risk by forming more soluble cysteine-drug complexes.
  evidence:
  - reference: PMID:32066273
    reference_title: "Evaluation and Medical Management of Patients with Cystine Nephrolithiasis: A Consensus Statement."
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "then using cystine-binding thiol drugs."
    explanation: This consensus statement supports cystine-binding thiol drugs for recurrent stone formation after conservative measures and alkalinization.
  - reference: PMID:31024870
    reference_title: A Case of Hypotonia-Cystinuria Syndrome With Genito-Urinary Malformations and Extrarenal Involvement.
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "Tiopronin (15 mg/kg/day) was immediately started, along with Potassium Citrate."
    explanation: This HCS case documents tiopronin use after biochemical cystinuria diagnosis.
- name: Pyridostigmine trial for PREPL-related myasthenic symptoms
  description: >
    Pyridostigmine may transiently improve PREPL-related myasthenic symptoms in
    early life, but reported response in HCS was limited and should be treated as
    partial evidence rather than established disease-modifying therapy.
  treatment_term:
    preferred_term: Pharmacotherapy
    term:
      id: NCIT:C15986
      label: Pharmacotherapy
    therapeutic_agent:
    - preferred_term: pyridostigmine
      term:
        id: NCIT:C76139
        label: Pyridostigmine
  target_mechanisms:
  - target: PREPL-related neuromuscular transmission defect
    treatment_effect: MODULATES
    description: Pyridostigmine may improve neuromuscular transmission symptoms in some PREPL-deficient patients.
  evidence:
  - reference: PMID:24610330
    reference_title: PREPL deficiency with or without cystinuria causes a novel myasthenic syndrome.
    supports: PARTIAL
    evidence_source: HUMAN_CLINICAL
    snippet: "She and 1 of 3 patients with HCS responded transiently to pyridostigmine during infancy."
    explanation: Response was transient and only observed in one of three HCS patients, so support is partial.
clinical_trials:
- name: NCT02640443
  phase: PHASE_II
  status: UNKNOWN
  description: >
    Phase 2 trial evaluating oral sulfamethoxazole for symptoms of primary PREPL
    deficiency, including hypotonia-cystinuria syndrome and isolated PREPL deficiency.
  target_phenotypes:
  - preferred_term: Generalized hypotonia
    term:
      id: HP:0001290
      label: Generalized hypotonia
  - preferred_term: Ptosis
    term:
      id: HP:0000508
      label: Ptosis
  - preferred_term: Muscle weakness
    term:
      id: HP:0001324
      label: Muscle weakness
  evidence:
  - reference: clinicaltrials:NCT02640443
    reference_title: "Sulfamethoxazole for the Treatment of Primary PREPL Deficiency"
    supports: SUPPORT
    evidence_source: HUMAN_CLINICAL
    snippet: "The investigators will evaluate whether sulfamethoxazole, a sulfamide antibiotic, improves the symptoms of primary PREPL deficiency (hypotonia-cystinuria syndrome and isolated PREPL deficiency)."
    explanation: The ClinicalTrials.gov record directly identifies the investigational PREPL deficiency therapy and includes HCS.
datasets:
📚

References & Deep Research

References

11
PMID:16385448
Deletion of PREPL, a gene encoding a putative serine oligopeptidase, in patients with hypotonia-cystinuria syndrome.
No top-level findings curated for this source.
PMID:22766003
2p21 Deletions in hypotonia-cystinuria syndrome.
No top-level findings curated for this source.
PMID:22796000
Two novel deletions in hypotonia-cystinuria syndrome.
No top-level findings curated for this source.
PMID:34612606
Hypotonia-cystinuria 2p21 deletion syndrome: Intrafamilial variability of clinical expression.
No top-level findings curated for this source.
PMID:31024870
A Case of Hypotonia-Cystinuria Syndrome With Genito-Urinary Malformations and Extrarenal Involvement.
No top-level findings curated for this source.
PMID:24610330
PREPL deficiency with or without cystinuria causes a novel myasthenic syndrome.
No top-level findings curated for this source.
PMID:28726805
PREPL deficiency: delineation of the phenotype and development of a functional blood assay.
No top-level findings curated for this source.
PMID:21222627
PREPL, a prolyl endopeptidase-like enzyme by name only?--Lessons from patients.
No top-level findings curated for this source.
PMID:22480232
Cystinuria: an inborn cause of urolithiasis.
No top-level findings curated for this source.
PMID:32066273
Evaluation and Medical Management of Patients with Cystine Nephrolithiasis: A Consensus Statement.
No top-level findings curated for this source.
clinicaltrials:NCT02640443
Sulfamethoxazole for the Treatment of Primary PREPL Deficiency (In Dutch: Sulfamethoxazole Ter Behandeling Van Primaire PREPL deficiëntie)
No top-level findings curated for this source.

Deep Research

1
Falcon ▸
Disease Characteristics Research Template
Edison Scientific Literature 24 citations 2026-05-08T12:33:11.471680

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: Hypotonia-cystinuria syndrome
  • MONDO ID: (if available)
  • Category: Mendelian

Research Objectives

Please provide a comprehensive research report on Hypotonia-cystinuria syndrome 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
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For each treatment, suggest MAXO (Medical Action Ontology) terms where applicable.

13. Prevention

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14. Other Species / Natural Disease

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  • Resources:
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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, MAXO, 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 (MAXO terms) - Evidence items with PMIDs and exact abstract quotes - Epidemiology, prognosis, diagnostic, and prevention information - Animal model descriptions with phenotype recapitulation details

Comprehensive Disease Characteristics Research Report: Hypotonia–cystinuria syndrome (HCS)

Executive summary

Hypotonia–cystinuria syndrome (HCS) is a very rare autosomal recessive contiguous-gene deletion disorder at chromosome 2p21, classically due to biallelic deletions disrupting SLC3A1 (type I cystinuria) and PREPL (neuromuscular/growth phenotype), producing neonatal/infantile hypotonia and biochemical cystinuria with risk of cystine nephrolithiasis. The condition sits on a deletion-size spectrum in 2p21 in which larger deletions (e.g., including CAMKMT/C2orf34 and/or PPM1B) can produce more severe multisystem disease. (eggermann20122p21deletionsin pages 1-2, eggermann2012cystinuriaaninborn pages 6-8, kılıc2018firstcardiacmanifestation pages 1-3, chabrol2008deletionofc2orf34 pages 2-3)

Item type Value Source (author/year/journal) URL/DOI Notes
Identifier OMIM 606407 Eggermann et al., 2012, European Journal of Medical Genetics https://doi.org/10.1016/j.ejmg.2012.06.008 HCS explicitly cited as “HCS; OMIM 606407”; autosomal recessive condition caused by 2p21 deletions disrupting SLC3A1 and PREPL (eggermann20122p21deletionsin pages 1-2)
Identifier OMIM 606407 Kılıç et al., 2018, Metabolic Brain Disease https://doi.org/10.1007/s11011-018-0226-2 Described as a “very rare autosomal recessive contiguous gene deletion disorder” due to combined microdeletions of SLC3A1 and PREPL at chromosome 2p21 (kılıc2018firstcardiacmanifestation pages 1-3)
Synonym Hypotonia-cystinuria syndrome Jaeken et al., 2006, American Journal of Human Genetics https://doi.org/10.1086/498852 Foundational naming paper referring to “the hypotonia-cystinuria syndrome”; associated with microdeletion involving 2p21 region and PREPL deletion (eggermann2012cystinuriaaninborn pages 6-8)
Synonym HCS Eggermann et al., 2012, European Journal of Medical Genetics https://doi.org/10.1016/j.ejmg.2012.06.008 Common abbreviation used in peer-reviewed literature for hypotonia-cystinuria syndrome (eggermann20122p21deletionsin pages 1-2)
Synonym Hypotonia–cystinuria 2p21 deletion syndrome Towheed et al., 2021, Annals of Clinical and Translational Neurology https://doi.org/10.1002/acn3.51464 Used for cases with homozygous 2p21 deletion involving SLC3A1 and PREPL; emphasizes chromosomal-deletion mechanism and intrafamilial variability (eggermann20122p21deletionsin pages 1-2)
Definition Rare autosomal recessive contiguous-gene deletion syndrome characterized by neonatal/infantile hypotonia and type I (type A) cystinuria Eggermann et al., 2012, European Journal of Medical Genetics https://doi.org/10.1016/j.ejmg.2012.06.008 Core lesion: chromosome 2p21 deletions disrupting SLC3A1 and PREPL; common features include generalized neonatal hypotonia, failure to thrive, growth retardation, and cystinuria (eggermann20122p21deletionsin pages 1-2)
Definition Syndromic form of cystinuria associated with homozygous contiguous deletions at 2p21 affecting at least SLC3A1 and PREPL Eggermann et al., 2012, Orphanet Journal of Rare Diseases https://doi.org/10.1186/1750-1172-7-19 Reported hallmarks: generalized hypotonia at birth, failure to thrive, growth retardation, cystinuria/nephrolithiasis; 13 patients and 5 different HCS deletions noted in review (eggermann2012cystinuriaaninborn pages 6-8)
Definition Very rare autosomal recessive contiguous gene deletion disorder caused by combined microdeletions of SLC3A1 and PREPL on chromosome 2p21 Kılıç et al., 2018, Metabolic Brain Disease https://doi.org/10.1007/s11011-018-0226-2 Additional commonly reported features include feeding problems, developmental delay, growth hormone deficiency, nephrolithiasis, and minor dysmorphism (kılıc2018firstcardiacmanifestation pages 1-3)
Definition Contiguous-gene disorder linked to 2p21 deletions disrupting SLC3A1 and PREPL, with phenotype intermediate to larger 2p21 deletion syndromes when only these two genes are involved Martens et al., 2008, Current Molecular Medicine https://doi.org/10.2174/156652408785747997 Larger deletions including PPM1B and/or C2orf34/CAMKMT produce more severe related syndromes; HCS specifically refers to deletions including SLC3A1 and PREPL (martens2008multisystemdisordersyndromes pages 2-3, chabrol2008deletionofc2orf34 pages 2-3)
Synonym/Related term Atypical hypotonia–cystinuria syndrome Chabrol et al., 2008, Journal of Medical Genetics https://doi.org/10.1136/jmg.2007.055475 Related but distinct phenotype caused by deletion encompassing SLC3A1, PREPL, and C2orf34/CAMKMT; useful for differential nomenclature, not identical to classic HCS (chabrol2008deletionofc2orf34 pages 2-3)

Table: This table summarizes the key disease identifiers, accepted names, and core disease definition for hypotonia-cystinuria syndrome using only supported evidence from the retrieved literature. It is useful for normalizing terminology and linking HCS to its characteristic 2p21 contiguous-gene deletion mechanism.

Genetic lesion category Genes involved (HGNC symbols) Genomic region Typical zygosity / inheritance Reported deletion sizes / ranges Key phenotypic correlates Key diagnostic methods Key sources (author/year) with DOI/URL
Classic HCS contiguous-gene deletion SLC3A1, PREPL 2p21 Usually homozygous; autosomal recessive ~38–127 kb across reported HCS deletions Generalized neonatal hypotonia, failure to thrive, growth retardation, cystinuria / nephrolithiasis Urine amino acid analysis; Sanger failure to amplify deleted exons; SNP microarray / molecular karyotyping Eggermann 2012, Eur J Med Genet; DOI: 10.1016/j.ejmg.2012.06.008; https://doi.org/10.1016/j.ejmg.2012.06.008 (eggermann20122p21deletionsin pages 1-2)
Classic HCS contiguous-gene deletion (reviewed series) SLC3A1, PREPL 2p21 Homozygous contiguous deletions; recessive disease mechanism Five different deletions; approximately ~38–127 kb; 13 reported patients Hypotonia at birth, failure to thrive, growth retardation, cystinuria / nephrolithiasis Molecular screening for SLC3A1 defects; deletion analysis in cystinuria workup Eggermann 2012, Orphanet J Rare Dis; DOI: 10.1186/1750-1172-7-19; https://doi.org/10.1186/1750-1172-7-19 (eggermann2012cystinuriaaninborn pages 6-8)
Atypical HCS with larger deletion SLC3A1, PREPL, C2orf34/CAMKMT 2p21 Familial genomic deletion; recessive presentation Breakpoints mapped from SLC3A1 intron 4 to C2orf34 intron 1; exact total size not stated in excerpt Severe neonatal hypotonia, poor sucking requiring nasogastric feeding, delayed motor milestones, psychomotor/growth retardation, cystinuria with nephrolithiasis Urinary amino acid chromatography; qPCR breakpoint mapping; junction-fragment sequencing Chabrol 2008, J Med Genet; DOI: 10.1136/jmg.2007.055475; https://doi.org/10.1136/jmg.2007.055475 (chabrol2008deletionofc2orf34 pages 2-3)
HCS / related 2p21 deletion spectrum SLC3A1, PREPL; larger related deletions may include PPM1B and C2orf34/CAMKMT 2p21 HCS: recessive contiguous-gene disorder; larger deletions associated with more severe related syndromes Initial HCS series identified recurrent deletions; severe related syndrome reported with ~179 kb homozygous deletion HCS: neonatal/infantile hypotonia, poor feeding, GH deficiency, type I cystinuria; larger deletions: neonatal seizures, severe developmental delay Genetic testing for 2p21 deletions and SLC3A1/PREPL analysis Martens 2008, Curr Mol Med; DOI: 10.2174/156652408785747997; https://doi.org/10.2174/156652408785747997 (martens2008multisystemdisordersyndromes pages 2-3)
Very rare autosomal recessive HCS due to combined microdeletions SLC3A1, PREPL (sometimes discussion includes neighboring genes in differential / expanded deletions) 2p21 Homozygous combined microdeletion; autosomal recessive Not quantified in excerpt; deletion detected by chromosomal microarray Infantile hypotonia, feeding problems, failure to thrive, short stature / GH deficiency, developmental delay, cystinuria type A; cardiac involvement reported as unusual extension Metabolic testing; urinary amino acid analysis; chromosomal microarray; echocardiography for extrarenal evaluation Kılıç 2018, Metab Brain Dis; DOI: 10.1007/s11011-018-0226-2; https://doi.org/10.1007/s11011-018-0226-2 (kılıc2018firstcardiacmanifestation pages 1-3, kılıc2018firstcardiacmanifestation pages 4-5)
Intrafamilial variable HCS with exon-level deletion SLC3A1 (exons 2–10), PREPL (exons 2–14) 2p21 Homozygous deletion; recessive Exon-level deletion reported; bp size not given in excerpt Congenital hypotonia, lactic acidosis, failure to thrive in infancy; later divergence to cystinuria/nephrolithiasis vs chronic neurobehavioral disturbance Whole-exome sequencing revealing homozygous 2p21 deletion; muscle biopsy / respiratory chain studies in differential workup Towheed 2021, Ann Clin Transl Neurol; DOI: 10.1002/acn3.51464; https://doi.org/10.1002/acn3.51464 (eggermann20122p21deletionsin pages 1-2)
Rare compound heterozygous mechanism within HCS spectrum SLC3A1, PREPL plus separate SLC3A1 deletion on other allele 2p21 Compound heterozygous at locus; functionally biallelic disruption Not stated Syndromic cystinuria with HCS phenotype supports need to evaluate CNVs plus single-gene defects Screening cystinuria patients for SLC3A1 mutations / deletions; deletion analysis Eggermann 2012, Orphanet J Rare Dis; DOI: 10.1186/1750-1172-7-19; https://doi.org/10.1186/1750-1172-7-19 (eggermann2012cystinuriaaninborn pages 6-8)
Mechanistic interpretation of classic HCS SLC3A1 loss explains type I cystinuria; PREPL loss implicated in hypotonia / growth phenotype 2p21 Recessive contiguous-gene loss Recurrent deletions summarized in reported families Renal amino acid transport defect with cystinuria from SLC3A1 deficiency; neuromuscular / growth manifestations linked to PREPL deficiency Combined biochemical and molecular testing; deletion-focused assays when syndromic features coexist with cystinuria Eggermann 2012; Martens 2008; Kılıç 2018 (eggermann20122p21deletionsin pages 1-2, martens2008multisystemdisordersyndromes pages 2-3, kılıc2018firstcardiacmanifestation pages 1-3)

Table: This table summarizes the known molecular basis of hypotonia-cystinuria syndrome across classic and atypical 2p21 deletion presentations. It is useful for linking gene content, deletion class, phenotype, and the most informative diagnostic methods in reported cases.

1. Disease information

1.1 What is the disease?

HCS is described as a “very rare autosomal recessive contiguous gene deletion disorder” caused by combined microdeletions of SLC3A1 and PREPL on chromosome 2p21, characterized by neonatal/infantile hypotonia and cystinuria (type A/type I) with nephrolithiasis risk, alongside growth and neurodevelopmental features. (eggermann20122p21deletionsin pages 1-2, kılıc2018firstcardiacmanifestation pages 1-3)

A key clinical caveat reported in case-based literature is that kidney stones may be absent in early infancy, which can delay diagnosis if clinicians do not recognize the syndromic combination of hypotonia + biochemical cystinuria. (taroni2019acaseof pages 2-3)

1.2 Key identifiers (best-available from retrieved sources)

  • OMIM: 606407 (explicitly used in multiple peer-reviewed sources) (eggermann20122p21deletionsin pages 1-2, kılıc2018firstcardiacmanifestation pages 1-3)
  • ICD-10/ICD-11 / MeSH / MONDO / Orphanet: Not available in the retrieved corpus using the provided tools; therefore not reported here.

1.3 Synonyms / alternative names

  • Hypotonia–cystinuria syndrome; HCS (eggermann20122p21deletionsin pages 1-2, kılıc2018firstcardiacmanifestation pages 1-3)
  • Hypotonia–cystinuria 2p21 deletion syndrome (used in literature emphasizing exon-level deletions and phenotypic variability) (eggermann20122p21deletionsin pages 1-2)
  • Related term (distinct entity): Atypical hypotonia–cystinuria syndrome (deletion includes SLC3A1–PREPL–CAMKMT/C2orf34) (chabrol2008deletionofc2orf34 pages 2-3)

1.4 Evidence provenance (patient-level vs aggregated)

The HCS knowledge base evidence is largely derived from: * Patient-level reports and small series defining deletion structure and clinical spectrum (e.g., atypical deletions; case reports with additional malformations). (chabrol2008deletionofc2orf34 pages 2-3, taroni2019acaseof pages 2-3) * Aggregated reviews summarizing number of reported cases and deletion classes (e.g., 13 reported HCS patients with five deletion classes). (eggermann2012cystinuriaaninborn pages 6-8)

2. Etiology

2.1 Disease causal factors

Primary cause: biallelic disruption of the 2p21 region affecting at least SLC3A1 and PREPL (most often homozygous deletions), causing combined renal amino-acid transport defect (cystinuria type I) and neuromuscular/growth phenotype. (eggermann20122p21deletionsin pages 1-2, eggermann2012cystinuriaaninborn pages 6-8, kılıc2018firstcardiacmanifestation pages 1-3)

Deletion-size spectrum / mechanistic stratification: * Classic HCS: SLC3A1 + PREPL deletions (~38–127 kb). (eggermann20122p21deletionsin pages 1-2, eggermann2012cystinuriaaninborn pages 6-8) * Atypical HCS: deletion includes CAMKMT/C2orf34 in addition to SLC3A1 + PREPL, with severe hypotonia/feeding difficulty and developmental delay. (chabrol2008deletionofc2orf34 pages 2-3) * Larger 2p21 deletions: inclusion of PPM1B is associated with more severe phenotypes (e.g., neonatal seizures, severe global developmental delay in related syndromes), consistent with gene-content modifying disease expression. (eggermann20122p21deletionsin pages 1-2, eggermann2012cystinuriaaninborn pages 6-8)

2.2 Risk factors

  • Genetic risk: autosomal recessive inheritance with homozygous or compound-heterozygous disruption at 2p21 involving SLC3A1 and PREPL. (eggermann20122p21deletionsin pages 1-2, eggermann2012cystinuriaaninborn pages 6-8)
  • Family structure: consanguinity is frequently present in recessive deletion syndromes in general; specific quantitative risk estimates were not extractable from the retrieved corpus.

2.3 Protective factors / gene–environment interactions

No HCS-specific protective factors or explicit gene–environment interactions were identified in the retrieved corpus. For the cystinuria component, conservative measures that reduce urinary cystine supersaturation (high urine volume, alkalinization, dietary sodium restriction) are widely described as preventive strategies for stone formation and recurrence. (d’ambrosio2022cystinuriaanupdate pages 1-3, d’ambrosio2022cystinuriaanupdate pages 4-5)

3. Phenotypes (clinical spectrum)

3.1 Core phenotype domains (human)

From clinical series and reviews, the most consistently reported features include:

Neuromuscular / neurodevelopmental * Generalized neonatal hypotonia (HP:0001252) (eggermann20122p21deletionsin pages 1-2, eggermann2012cystinuriaaninborn pages 6-8, kılıc2018firstcardiacmanifestation pages 1-3) * Feeding difficulties / poor sucking (HP:0011968 / HP:0002039), sometimes requiring nasogastric feeding in severe presentations (chabrol2008deletionofc2orf34 pages 2-3) * Developmental delay (HP:0001263) (kılıc2018firstcardiacmanifestation pages 1-3, taroni2019acaseof pages 2-3)

Growth / endocrine * Failure to thrive (HP:0001508) and growth retardation/short stature (HP:0004322) (eggermann20122p21deletionsin pages 1-2, eggermann2012cystinuriaaninborn pages 6-8, kılıc2018firstcardiacmanifestation pages 1-3) * Growth hormone deficiency (HP:0000824) is repeatedly cited as part of the phenotype; growth response to GH therapy is noted in reviews (martens2008multisystemdisordersyndromes pages 2-3, boonen2011preplaprolyl pages 1-3)

Renal / metabolic (cystinuria type I/type A) * Cystinuria / hyperexcretion of dibasic amino acids in urine (HP:0003355; also consider “Aminoaciduria” HP:0003354) (eggermann20122p21deletionsin pages 1-2, chabrol2008deletionofc2orf34 pages 2-3) * Nephrolithiasis (cystine stones) (HP:0000787). A case report documented stone analysis as “100% cystine” and provided a markedly elevated cystine/creatinine ratio (676 mMol/mol; normal 4–15). (taroni2019acaseof pages 2-3)

Other reported/expanded features (case-based) * Congenital anomalies of kidney and urinary tract (CAKUT) including primary obstructed megaureter (HP:0000079/HP:0002015-related), cryptorchidism (HP:0000028), and cardiac findings (e.g., patent foramen ovale with atrial septal aneurysm in one case report). (taroni2019acaseof pages 2-3) * Cardiac involvement (rare): a report described left ventricular non-compaction/dilated cardiomyopathy in HCS. (kılıc2018firstcardiacmanifestation pages 1-3)

Phenotype frequency / statistics Quantitative phenotype frequencies are limited in the retrieved corpus. One review excerpt indicates broad clinical patterns across reported families and notes a finite number of reported deletions and families, but does not provide per-phenotype percentages in the retrieved text. (boonen2011preplaprolyl pages 1-3, eggermann2012cystinuriaaninborn pages 6-8)

3.2 Age of onset and progression

  • Onset: typically congenital/neonatal for hypotonia and feeding problems; cystinuria is biochemical and may precede overt stone disease. (eggermann20122p21deletionsin pages 1-2, taroni2019acaseof pages 2-3)
  • Progression: renal stone disease may emerge later in childhood; intrafamilial variability is described, with divergence in later childhood manifestations even with the same deletion. (eggermann20122p21deletionsin pages 1-2)

3.3 Quality of life impact

No standardized QoL instrument results (e.g., PedsQL, PROMIS) were extractable for HCS specifically; however, cystine stone disease is described as requiring chronic prevention and often repeated surgical interventions in cystinuria reviews, implying sustained morbidity. (d’ambrosio2022cystinuriaanupdate pages 1-3)

3.4 Suggested ontology mappings

HPO (examples): * HP:0001252 Hypotonia * HP:0001508 Failure to thrive * HP:0001263 Global developmental delay * HP:0000787 Nephrolithiasis * HP:0003355 Cystinuria (or HP:0003354 Aminoaciduria) * HP:0000028 Cryptorchidism (reported in one case)

4. Genetic / molecular information

4.1 Causal genes and molecular lesion types

Primary causal genes (contiguous deletion): * SLC3A1 (cystinuria type I) and PREPL (hypotonia/growth phenotype contribution) in the classic HCS definition. (eggermann20122p21deletionsin pages 1-2, eggermann2012cystinuriaaninborn pages 6-8, kılıc2018firstcardiacmanifestation pages 1-3)

Variant class: * Predominantly copy-number losses (microdeletions) at 2p21, usually homozygous; compound heterozygosity (deletion on one allele plus another deletion in SLC3A1) is also described within the HCS/cystinuria spectrum. (eggermann2012cystinuriaaninborn pages 6-8)

Deletion size / gene content: * Reported HCS deletions range approximately ~38–127 kb and consistently affect SLC3A1 and PREPL in the retrieved sources. (eggermann20122p21deletionsin pages 1-2, eggermann2012cystinuriaaninborn pages 6-8) * Larger deletions including additional genes (e.g., CAMKMT/C2orf34, PPM1B) define related syndromes and can worsen phenotype severity. (eggermann2012cystinuriaaninborn pages 6-8, chabrol2008deletionofc2orf34 pages 2-3)

4.2 Functional consequences (current understanding)

  • SLC3A1 encodes the heavy subunit (rBAT) of the renal transporter system responsible for reabsorption of cystine and dibasic amino acids; loss causes cystinuria and cystine stone formation. (d’ambrosio2022cystinuriaanupdate pages 1-3)
  • PREPL is described as encoding a putative serine oligopeptidase-like protein; loss is implicated in hypotonia and growth issues in HCS, and PREPL enzyme activity testing is being operationalized in clinical research settings. (eggermann20122p21deletionsin pages 1-2, NCT02263781 chunk 1)

4.3 Modifier genes, epigenetics

No HCS-specific modifier genes or epigenetic mechanisms were identified in the retrieved corpus; deletion gene-content effects (e.g., inclusion of PPM1B) function as a structural “modifier” via contiguous gene loss. (eggermann2012cystinuriaaninborn pages 6-8)

5. Environmental information

HCS itself is genetic. No external environmental triggers were identified. For the cystinuria component, dietary sodium/protein and hydration status are recognized modifiers of stone risk in cystinuria reviews and are targeted in management. (d’ambrosio2022cystinuriaanupdate pages 4-5)

6. Mechanism / pathophysiology

6.1 Causal chain (integrated)

  1. Genetic trigger: homozygous (or compound heterozygous) 2p21 deletion disrupting SLC3A1 and PREPL. (eggermann20122p21deletionsin pages 1-2, eggermann2012cystinuriaaninborn pages 6-8)
  2. Renal transport defect: SLC3A1 loss impairs proximal tubular reabsorption of cystine/dibasic amino acids → elevated urinary cystine. (d’ambrosio2022cystinuriaanupdate pages 1-3)
  3. Biophysical precipitation: cystine has low solubility at physiologic urine pH → supersaturation leads to crystal formation and cystine stones. (d’ambrosio2022cystinuriaanupdate pages 1-3)
  4. Clinical renal phenotype: recurrent nephrolithiasis, potential obstructive uropathy and interventions. (taroni2019acaseof pages 2-3)
  5. Neuromuscular phenotype: PREPL loss is implicated in congenital/neonatal hypotonia, feeding difficulty, and growth/endocrine issues, though the precise biochemical pathway is incompletely defined in the retrieved corpus. (eggermann20122p21deletionsin pages 1-2, NCT02263781 chunk 1)

6.2 Suggested GO / CL terms (best-effort mappings)

GO biological processes (examples): * Amino acid transmembrane transport * Renal tubule development / kidney development (for CAKUT cases) * Skeletal muscle contraction / neuromuscular process controlling balance

Cell Ontology (CL) candidates: * Renal proximal tubular epithelial cell * Skeletal muscle fiber / myocyte

(These ontology suggestions are conceptual mappings; the retrieved corpus did not provide explicit GO/CL term annotations.)

7. Anatomical structures affected

Organ/tissue systems (inferred from clinical phenotype)

  • Kidney/urinary tract (nephrolithiasis; obstructive megaureter in a case) (UBERON:0002113 kidney; UBERON:0000056 ureter) (taroni2019acaseof pages 2-3)
  • Skeletal muscle / neuromuscular system (hypotonia) (UBERON:0001134 skeletal muscle organ) (eggermann20122p21deletionsin pages 1-2, kılıc2018firstcardiacmanifestation pages 1-3)
  • Endocrine axis (growth hormone deficiency) (UBERON:0000007 pituitary gland) (kılıc2018firstcardiacmanifestation pages 1-3)
  • Heart (rare involvement in case reports) (UBERON:0000948 heart) (kılıc2018firstcardiacmanifestation pages 1-3)

8. Temporal development (natural history)

  • Neonatal period: hypotonia and feeding difficulty often dominate early presentation. (eggermann20122p21deletionsin pages 1-2, chabrol2008deletionofc2orf34 pages 2-3)
  • Infancy/childhood: cystinuria may be present biochemically; nephrolithiasis can develop later; variable neurobehavioral or other features may become apparent. (eggermann20122p21deletionsin pages 1-2, taroni2019acaseof pages 2-3)

9. Inheritance and population

9.1 Inheritance

HCS is consistently described as autosomal recessive, most often due to homozygous deletions at 2p21 involving SLC3A1 and PREPL. (eggermann20122p21deletionsin pages 1-2, kılıc2018firstcardiacmanifestation pages 1-3)

9.2 Epidemiology (best-available)

Formal prevalence/incidence estimates for HCS are not robust in the retrieved corpus. One report provides a model-based estimate tied to a deletion allele frequency (“reported incidence … 1/1000000 for an allele frequency of 1/1000 for deletion B”). (kılıc2018firstcardiacmanifestation pages 1-3)

A review also summarized that “Thirteen HCS patients have been reported” and “five different HCS deletions have been identified,” indicating extreme rarity and reliance on reported cases. (eggermann2012cystinuriaaninborn pages 6-8)

10. Diagnostics

10.1 Clinical and laboratory diagnosis

Key tests used in case reports and reviews include: * Urinary amino acid analysis / chromatography showing increased cystine, lysine, arginine, ornithine (cystinuria biochemical signature). (eggermann20122p21deletionsin pages 1-2, chabrol2008deletionofc2orf34 pages 2-3) * Stone analysis (when stones are present), e.g., “100% cystine” in one case report. (taroni2019acaseof pages 2-3)

10.2 Genetic testing

Given that HCS is a CNV-driven contiguous-gene disorder, informative methods include: * Chromosomal microarray / SNP microarray / molecular karyotyping to detect and size 2p21 deletions. (eggermann20122p21deletionsin pages 1-2, kılıc2018firstcardiacmanifestation pages 1-3) * MLPA targeted to SLC3A1/PREPL deletions (used in a case report). (taroni2019acaseof pages 2-3) * qPCR and breakpoint sequencing for detailed deletion characterization (atypical HCS). (chabrol2008deletionofc2orf34 pages 2-3)

10.3 Differential diagnosis

Because early HCS can present with hypotonia and feeding difficulties, differential workups may include neuromuscular disorders or syndromes with hypotonia/FTT; a review notes that overlap may prompt exclusion of Prader–Willi syndrome in practice. (boonen2011preplaprolyl pages 1-3)

11. Outcome / prognosis

HCS-specific long-term survival and renal outcomes data were not extractable as population statistics from the retrieved corpus. Case-level data indicate that early recognition may influence neurologic and renal outcomes by enabling earlier cystinuria prevention strategies and appropriate supportive therapies. (taroni2019acaseof pages 2-3)

12. Treatment

12.1 Management principles (renal/stone prevention; extrapolated from cystinuria evidence)

Because HCS includes type I cystinuria, standard cystinuria therapy is directly relevant: * High urine volume + alkalinization as first-line: A 2024 systematic review states that first-line therapies “including high fluid intake and urinary alkalinization, increased urine volume to >3 L/day and urinary pH >7.0,” and were associated with reduced urinary cystine levels and cystine stone formation. (bhatt2024pharmacologicalinterventionsfor pages 1-3) * Second-line cystine-binding thiol drugs: The same review reports second-line therapy with “tiopronin and D-penicillamine” reduced urinary cystine and stone formation/recurrence. (bhatt2024pharmacologicalinterventionsfor pages 1-3)

Example quantitative outcomes (cystinuria literature): tiopronin-treated adults had lower urinary cystine than untreated (154.3 mg/L vs 422.4 mg/L, p=0.004), and adherence was associated with higher stone-free rates (73% vs 33%). (bhatt2024pharmacologicalinterventionsfor pages 10-11)

12.2 HCS case-based implementations

A case report of HCS with CAKUT used: * Potassium citrate (alkalinization) and tiopronin 15 mg/kg/day, plus urologic surgeries for obstructive uropathy and stone management (nephrolithotripsy/stone removal). (taroni2019acaseof pages 2-3)

12.3 Growth / hypotonia management

Reviews of the HCS phenotype report growth hormone deficiency as a common feature and note that GH therapy can improve growth outcomes (statement summarized in reviews; quantitative effect sizes not extractable from the retrieved corpus). (martens2008multisystemdisordersyndromes pages 2-3, boonen2011preplaprolyl pages 1-3)

12.4 Experimental/clinical research (trials)

Two ClinicalTrials.gov studies directly address PREPL deficiency (including HCS):

  • NCT02640443 (Phase 2): “Sulfamethoxazole for the Treatment of Primary PREPL Deficiency” evaluates whether sulfamethoxazole improves PREPL deficiency symptoms; dosing is oral sulfamethoxazole 60 mg/kg/day (max 3 g) for 3 weeks, with outcomes centered on ptosis/facial indices and broader neuromuscular/neuropsychological and renal ultrasound endpoints. (NCT02640443 chunk 1)

Direct quote (registry): the objective is “to evaluate whether sulfamethoxazole … improves symptoms of PREPL deficiency.” (NCT02640443 chunk 1)

  • NCT02263781 (diagnostic/physiology): “PREPL in Health and Disease” measures PREPL enzyme activity in blood (and in a subset, muscle) to establish normal pediatric values and compare PREPL activity across controls, Prader–Willi syndrome, and primary PREPL deficiency. (NCT02263781 chunk 1)

Direct quote (registry content paraphrase): primary outcomes focus on PREPL activity expressed as “ng active PREPL/g protein” and comparisons between groups. (NCT02263781 chunk 1)

12.5 MAXO suggestions (examples)

  • MAXO: high fluid intake therapy (for nephrolithiasis prevention)
  • MAXO: urinary alkalinization therapy (e.g., potassium citrate)
  • MAXO: cystine-binding thiol therapy (tiopronin / D-penicillamine)
  • MAXO: growth hormone replacement therapy
  • MAXO: physical therapy / feeding support

13. Prevention

No primary prevention exists for the genetic cause, but secondary/tertiary prevention targets the cystinuria component: * Maintain high urine volume and urinary alkalinization to prevent cystine precipitation and reduce recurrence. (bhatt2024pharmacologicalinterventionsfor pages 1-3, d’ambrosio2022cystinuriaanupdate pages 4-5) * Monitor urinary pH/cystine-related measures and imaging for stones (review emphasizes regular monitoring; specific schedules vary). (bhatt2024pharmacologicalinterventionsfor pages 1-3, d’ambrosio2022cystinuriaanupdate pages 5-6)

14. Other species / natural disease

No naturally occurring non-human HCS analogs were identified in the retrieved corpus.

15. Model organisms

No dedicated HCS model organism evidence was successfully retrieved in the current tool runs; therefore, model organism section is incomplete.

Figures/tables from retrieved primary case report

A schematic of reported 2p21 deletions and a clinical-feature table were retrieved from the HCS case report and can support KB curation of deletion boundaries and phenotypic fields. (taroni2019acaseof media 9faf13df, taroni2019acaseof media d28b2f89)

Notes on evidence limitations (PMID requirement)

Several key sources in the retrieved corpus are peer-reviewed and include DOI/URLs, but PMIDs were not available in the extracted text for many items. Where PMID is required, manual PubMed crosswalk would be needed beyond current tool outputs. This report therefore provides DOI/URLs and publication metadata for traceability.

References

  1. (eggermann20122p21deletionsin pages 1-2): Thomas Eggermann, Sabrina Spengler, Andreas Venghaus, Bernd Denecke, Klaus Zerres, Michael Baudis, and Regina Ensenauer. 2p21 deletions in hypotonia-cystinuria syndrome. European journal of medical genetics, 55 10:561-3, Oct 2012. URL: https://doi.org/10.1016/j.ejmg.2012.06.008, doi:10.1016/j.ejmg.2012.06.008. This article has 18 citations and is from a peer-reviewed journal.

  2. (eggermann2012cystinuriaaninborn pages 6-8): Thomas Eggermann, Andreas Venghaus, and Klaus Zerres. Cystinuria: an inborn cause of urolithiasis. Orphanet Journal of Rare Diseases, 7:19-19, Apr 2012. URL: https://doi.org/10.1186/1750-1172-7-19, doi:10.1186/1750-1172-7-19. This article has 160 citations and is from a peer-reviewed journal.

  3. (kılıc2018firstcardiacmanifestation pages 1-3): Mustafa Kılıç, Ahmet Cevdet Ceylan, Utku Arman Örün, and Esra Kılıç. First cardiac manifestation of hypotonia-cystinuria syndrome. Metabolic Brain Disease, 33:1375-1379, Apr 2018. URL: https://doi.org/10.1007/s11011-018-0226-2, doi:10.1007/s11011-018-0226-2. This article has 5 citations and is from a peer-reviewed journal.

  4. (chabrol2008deletionofc2orf34 pages 2-3): B. Chabrol, Katrin Martens, S. Meulemans, Aline Cano, Jaak Jaeken, G. Matthijs, and John W. M. Creemers. Deletion of c2orf34, prepl and slc3a1 causes atypical hypotonia–cystinuria syndrome. Journal of Medical Genetics, 45:314-318, Jan 2008. URL: https://doi.org/10.1136/jmg.2007.055475, doi:10.1136/jmg.2007.055475. This article has 62 citations and is from a domain leading peer-reviewed journal.

  5. (martens2008multisystemdisordersyndromes pages 2-3): Kevin Martens, Jaak Jaeken, Gert Matthijs, and John Creemers. Multi-system disorder syndromes associated with cystinuria type i. Current Molecular Medicine, 8:544-550, Sep 2008. URL: https://doi.org/10.2174/156652408785747997, doi:10.2174/156652408785747997. This article has 31 citations and is from a peer-reviewed journal.

  6. (kılıc2018firstcardiacmanifestation pages 4-5): Mustafa Kılıç, Ahmet Cevdet Ceylan, Utku Arman Örün, and Esra Kılıç. First cardiac manifestation of hypotonia-cystinuria syndrome. Metabolic Brain Disease, 33:1375-1379, Apr 2018. URL: https://doi.org/10.1007/s11011-018-0226-2, doi:10.1007/s11011-018-0226-2. This article has 5 citations and is from a peer-reviewed journal.

  7. (taroni2019acaseof pages 2-3): Francesca Taroni, Valentina Capone, Alfredo Berrettini, Erika Adalgisa De Marco, Gian Antonio Manzoni, and Giovanni Montini. A case of hypotonia-cystinuria syndrome with genito-urinary malformations and extrarenal involvement. Frontiers in Pediatrics, Apr 2019. URL: https://doi.org/10.3389/fped.2019.00127, doi:10.3389/fped.2019.00127. This article has 4 citations.

  8. (d’ambrosio2022cystinuriaanupdate pages 1-3): Viola D’Ambrosio, Giovanna Capolongo, David Goldfarb, Giovanni Gambaro, and Pietro Manuel Ferraro. Cystinuria: an update on pathophysiology, genetics, and clinical management. Pediatric Nephrology, 37:1705-1711, Nov 2022. URL: https://doi.org/10.1007/s00467-021-05342-y, doi:10.1007/s00467-021-05342-y. This article has 55 citations and is from a domain leading peer-reviewed journal.

  9. (d’ambrosio2022cystinuriaanupdate pages 4-5): Viola D’Ambrosio, Giovanna Capolongo, David Goldfarb, Giovanni Gambaro, and Pietro Manuel Ferraro. Cystinuria: an update on pathophysiology, genetics, and clinical management. Pediatric Nephrology, 37:1705-1711, Nov 2022. URL: https://doi.org/10.1007/s00467-021-05342-y, doi:10.1007/s00467-021-05342-y. This article has 55 citations and is from a domain leading peer-reviewed journal.

  10. (boonen2011preplaprolyl pages 1-3): Kurt Boonen, Luc Regal, Jaak Jaeken, and John W.M. Creemers. Prepl, a prolyl endopeptidase-like enzyme by name only? – lessons from patients. CNS & Neurological Disorders - Drug Targets, 10:355-360, May 2011. URL: https://doi.org/10.2174/187152711794653760, doi:10.2174/187152711794653760. This article has 21 citations.

  11. (NCT02263781 chunk 1): PREPL in Health and Disease. Universitaire Ziekenhuizen KU Leuven. 2014. ClinicalTrials.gov Identifier: NCT02263781

  12. (bhatt2024pharmacologicalinterventionsfor pages 1-3): Nirmal Prasad Bhatt, Aniruddh Vijay Deshpande, and Malcolm Ronald Starkey. Pharmacological interventions for the management of cystinuria: a systematic review. Journal of Nephrology, 37:293-308, Nov 2024. URL: https://doi.org/10.1007/s40620-023-01795-6, doi:10.1007/s40620-023-01795-6. This article has 21 citations and is from a peer-reviewed journal.

  13. (bhatt2024pharmacologicalinterventionsfor pages 10-11): Nirmal Prasad Bhatt, Aniruddh Vijay Deshpande, and Malcolm Ronald Starkey. Pharmacological interventions for the management of cystinuria: a systematic review. Journal of Nephrology, 37:293-308, Nov 2024. URL: https://doi.org/10.1007/s40620-023-01795-6, doi:10.1007/s40620-023-01795-6. This article has 21 citations and is from a peer-reviewed journal.

  14. (NCT02640443 chunk 1): Sulfamethoxazole for the Treatment of Primary PREPL Deficiency. Universitair Ziekenhuis Brussel. 2015. ClinicalTrials.gov Identifier: NCT02640443

  15. (d’ambrosio2022cystinuriaanupdate pages 5-6): Viola D’Ambrosio, Giovanna Capolongo, David Goldfarb, Giovanni Gambaro, and Pietro Manuel Ferraro. Cystinuria: an update on pathophysiology, genetics, and clinical management. Pediatric Nephrology, 37:1705-1711, Nov 2022. URL: https://doi.org/10.1007/s00467-021-05342-y, doi:10.1007/s00467-021-05342-y. This article has 55 citations and is from a domain leading peer-reviewed journal.

  16. (taroni2019acaseof media 9faf13df): Francesca Taroni, Valentina Capone, Alfredo Berrettini, Erika Adalgisa De Marco, Gian Antonio Manzoni, and Giovanni Montini. A case of hypotonia-cystinuria syndrome with genito-urinary malformations and extrarenal involvement. Frontiers in Pediatrics, Apr 2019. URL: https://doi.org/10.3389/fped.2019.00127, doi:10.3389/fped.2019.00127. This article has 4 citations.

  17. (taroni2019acaseof media d28b2f89): Francesca Taroni, Valentina Capone, Alfredo Berrettini, Erika Adalgisa De Marco, Gian Antonio Manzoni, and Giovanni Montini. A case of hypotonia-cystinuria syndrome with genito-urinary malformations and extrarenal involvement. Frontiers in Pediatrics, Apr 2019. URL: https://doi.org/10.3389/fped.2019.00127, doi:10.3389/fped.2019.00127. This article has 4 citations.