| Domain | Evidence-backed finding | Suggested ontology/code | Evidence type/strength |
|---|---|---|---|
| Disease identifiers | Schaaf-Yang syndrome (SYS) is a rare Mendelian neurodevelopmental/imprinting disorder; OMIM 615547; Open Targets disease mapping supports MONDO_0014243; overlaps partly with Prader-Willi syndrome but is clinically distinct (pqac-00000000, pqac-00000002) | MONDO: Schaaf-Yang syndrome; OMIM: 615547; category: Mendelian disease; candidate MeSH/Orphanet labels: Schaaf-Yang syndrome | Human peer-reviewed review/original synthesis + curated database association; moderate-strong |
| Synonyms / naming | Common names include Schaaf-Yang syndrome and SYS; older literature may describe a Prader-Willi-like syndrome with arthrogryposis due to MAGEL2 (pqac-00000002) | candidate synonyms: SYS; MAGEL2-related Schaaf-Yang syndrome | Human literature synthesis; moderate |
| Causal gene / imprinting | Disease is caused primarily by truncating variants in MAGEL2 on 15q11-q13 affecting the paternally expressed allele; maternal allele is imprinted/silenced, so parental-origin confirmation is clinically important (pqac-00000002, pqac-00000006) | Gene: MAGEL2; chromosome region: 15q11-q13; inheritance concept: autosomal dominant with genomic imprinting / paternal expression | Human molecular genetics; strong |
| Variant class | Reported disease-causing variants are predominantly nonsense or frameshift truncating variants; truncated protein lacks the MAGE homology domain (pqac-00000002, pqac-00000006) | sequence_variant classes: nonsense_variant; frameshift_variant; truncating variant; loss-of-function with possible neomorphic effect | Human molecular genetics + in vitro functional evidence; strong |
| Pathogenic mechanism summary | MAGEL2 normally participates in retrograde transport and endosomal protein recycling; SYS likely reflects both loss of MAGEL2 function and pathogenic effects of a stable truncated protein (pqac-00000002, pqac-00000006, pqac-00000008) | GO candidate terms: endosomal transport; retrograde transport, endosome to trans-Golgi network; protein recycling; regulated exocytosis / neuropeptide secretion | Human original research + mechanistic interpretation; moderate-strong |
| Truncated protein behavior | In cell studies, truncated MAGEL2 was stable and shifted from mainly cytoplasmic WT localization to predominantly nuclear localization, supporting a possible neomorphic/toxic mechanism beyond simple haploinsufficiency (pqac-00000006, pqac-00000008) | GO cellular component candidates: nucleus; cytoplasm; endosome; protein localization abnormality | In vitro functional study; moderate |
| Transcriptomic profile | Patient fibroblasts showed 132 differentially expressed genes, including ncRNAs; HOTAIR was highlighted as upregulated and proposed as a candidate biomarker (pqac-00000006, pqac-00000007) | biomarker candidates: HOTAIR mRNA; transcriptomic signature; ncRNA dysregulation | Human patient-derived in vitro omics; moderate |
| Metabolomic / biochemical profile | SYS fibroblasts had significantly decreased intracellular glutamine and decreased secretion of amyloid-β1-40 (Aβ1-40); both were proposed as candidate biomarkers, but remain unvalidated clinically (pqac-00000006, pqac-00000008) | CHEBI candidate: glutamine; biomarker candidates: Aβ1-40 secretion, glutamine level | Human patient-derived in vitro metabolomics; moderate |
| Core phenotype overview | Early-onset phenotype commonly includes neonatal hypotonia, developmental delay/intellectual disability, feeding difficulties, endocrine disturbance, sleep problems, autism spectrum features, and joint contractures/arthrogryposis (pqac-00000002, pqac-00000004) | HPO candidates: Neonatal hypotonia; Global developmental delay; Intellectual disability; Feeding difficulties; Autism; Arthrogryposis multiplex congenita / Camptodactyly; Sleep disturbance | Human cohort/literature synthesis; strong |
| Facial dysmorphism frequency | Facial dysmorphism reported in 91.4% (64/70) of cases in compiled cohort data (pqac-00000005) | HPO candidate: Abnormal facial shape / Facial dysmorphism | Human compiled cohort frequency; moderate |
| Sleep disturbance frequency | Sleep disturbance reported in 100% (13/13) of cases with available data in compiled cohort review (pqac-00000005) | HPO candidate: Sleep disturbance; sleep-disordered breathing candidate | Human compiled cohort frequency; moderate, small denominator |
| Growth hormone deficiency frequency | Growth hormone deficiency reported in 72.7% (16/22) of assessed individuals (pqac-00000005) | HPO candidate: Growth hormone deficiency; endocrine abnormality | Human compiled cohort frequency; moderate, small denominator |
| Camptodactyly / contracture frequency | Camptodactyly reported in 50% of compiled cases; contractures/arthrogryposis are a distinguishing SYS feature relative to classic PWS (pqac-00000005, pqac-00000002) | HPO candidates: Camptodactyly; Arthrogryposis multiplex congenita; Joint contracture | Human cohort + review; moderate-strong |
| Hypogonadism frequency | Hypogonadism reported in 50% (40/80) of compiled cases (pqac-00000005) | HPO candidate: Hypogonadism | Human compiled cohort frequency; moderate |
| Other endocrine frequencies | Hypothyroidism 29.6%; hypoglycemia 63.6%; temperature instability 62.9%; diabetes insipidus 29.4% in available compiled data (pqac-00000005) | HPO candidates: Hypothyroidism; Hypoglycemia; Temperature instability; Diabetes insipidus | Human compiled cohort frequency; moderate |
| Hormonal/metabolic phenotype | Review evidence notes elevated fasting ghrelin, low IGF-1, increased glucose intolerance/diabetes mellitus prevalence, scoliosis ~33%, abnormal bone mineral density, and that only a minority develop hyperphagia/obesity compared with PWS (pqac-00000003, pqac-00000007) | HPO candidates: Elevated circulating ghrelin; Low IGF-1; Glucose intolerance; Diabetes mellitus; Scoliosis; Decreased bone mineral density; Hyperphagia; Obesity | Review synthesizing human studies; moderate |
| Neurobehavioral phenotype | Autism spectrum disorder and more severe intellectual disability are emphasized as relatively more common/severe in SYS than in PWS (pqac-00000002, pqac-00000003) | HPO candidates: Autism; Intellectual disability; Behavioral abnormality | Human review/cohort synthesis; moderate-strong |
| Anatomy: brain / hypothalamus | MAGEL2 is expressed predominantly in brain, especially amygdala and hypothalamic nuclei including suprachiasmatic, paraventricular, and supraoptic nuclei; hypothalamic dysfunction is central to pathophysiology (pqac-00000002, pqac-00000007) | UBERON candidates: brain; hypothalamus; amygdala; paraventricular nucleus of hypothalamus; supraoptic nucleus; suprachiasmatic nucleus | Human expression/review evidence; moderate |
| Anatomy: pituitary developmental relevance | Embryonic MAGEL2 transcripts were found in developing hypothalamus/ventral diencephalon and Rathke's pouch, supporting hypothalamo-pituitary developmental involvement and congenital hypopituitarism risk (pqac-00000002) | UBERON candidates: Rathke pouch; pituitary gland; ventral diencephalon | Human embryonic expression study; moderate |
| Anatomy: muscle / musculoskeletal system | Hypotonia, high fat mass with low muscle tone, scoliosis, and joint contractures implicate skeletal muscle and musculoskeletal development/function (pqac-00000003, pqac-00000009) | UBERON candidates: skeletal muscle tissue; musculoskeletal system; vertebral column; joint | Human review + animal references; moderate |
| Cell types implicated | Most plausible disease-relevant cell types are hypothalamic neuroendocrine neurons and broader central neurons; fibroblasts are currently the main patient-derived experimental cell system; muscle cells are implicated by hypotonia phenotype (pqac-00000002, pqac-00000006, pqac-00000009) | CL candidates: neuron; hypothalamic neuroendocrine cell; fibroblast; skeletal muscle cell | Mixed human expression/in vitro/phenotype inference; moderate |
| Upstream-to-downstream causal chain | Paternal MAGEL2 truncation → impaired endosomal recycling / secretory trafficking and altered nuclear localization of truncated protein → hypothalamic neuroendocrine dysfunction and delayed neuronal maturation/synaptic abnormalities → neonatal hypotonia, feeding/respiratory/endocrine abnormalities, developmental delay, autism traits, contractures (pqac-00000002, pqac-00000006, pqac-00000007) | GO candidates: neuron development; synapse organization; peptide hormone secretion; endosomal transport; regulated exocytosis | Integrative mechanistic model from human and animal evidence; moderate |
| Synaptic / neuronal maturation evidence | Magel2-deficient mice show reduced neurite outgrowth, reduced glutamatergic synapse markers, and delayed neuronal maturation; oxytocin reversed neurite outgrowth abnormalities in culture (pqac-00000009) | GO candidates: neurite development; glutamatergic synaptic transmission; synapse maturation | Animal + in vitro preclinical evidence; moderate |
| Diagnostic approach | Best current diagnostic route is NGS-based sequencing (single gene, panel, exome, genome) detecting MAGEL2 truncating variants, followed by confirmation of paternal origin because maternal allele is imprinted; phenotype-first clues include neonatal hypotonia, feeding issues, contractures, developmental delay/autism, endocrine/sleep abnormalities (pqac-00000002, pqac-00000006) | Diagnostic concepts: sequence analysis of MAGEL2; trio exome/genome; parental-origin confirmation; genomic imprinting assessment | Human clinical genetics guidance; strong |
| Differential diagnosis | Major differential diagnoses include Prader-Willi syndrome, congenital hypopituitarism syndromes, and historically Opitz-C syndrome / PWS-like disorders with arthrogryposis (pqac-00000004, pqac-00000002) | candidate disease terms: Prader-Willi syndrome; congenital hypopituitarism; Opitz-C syndrome | Human literature synthesis; moderate |
| Real-world management | Management is multidisciplinary and symptomatic: neonatal feeding/airway/respiratory support, developmental therapies, autism-informed behavioral care, endocrine evaluation, orthopedic surveillance, and sleep monitoring; recent literature offers practical management guidelines by life stage (pqac-00000002, pqac-00000005) | MAXO candidates: respiratory support; feeding support; physical therapy; occupational therapy; speech therapy; endocrine system monitoring; orthopedic monitoring; sleep study | Human peer-reviewed management synthesis; moderate-strong |
| Growth hormone treatment | Growth hormone deficiency is common and patients may benefit from GH therapy; recent literature references retrospective and multi-year follow-up studies, but robust controlled efficacy/safety data remain limited (pqac-00000005, pqac-00000007, pqac-00000010) | MAXO candidates: growth hormone replacement therapy; endocrine follow-up | Human cohort/review evidence; moderate but incomplete |
| Sleep / respiratory management | Sleep disturbance is common and sleep-disordered breathing/polysomnography have been specifically studied in referenced literature; respiratory and sleep surveillance are therefore reasonable parts of care (pqac-00000005, pqac-00000009) | MAXO candidates: polysomnography; sleep-disordered breathing monitoring; respiratory management | Human literature synthesis; moderate |
| Prognosis / mortality | Disease is lifelong; available compiled literature notes 10-13 documented deaths in infancy/childhood, but precise survival estimates and causes-of-death distributions are not yet well established (pqac-00000005, pqac-00000004) | outcome concepts: childhood mortality; chronic neurodevelopmental disability | Human compiled literature; weak-moderate due to sparse data |
| Prevention / counseling | No primary prevention exists for de novo disease occurrence; for affected families, genetic counseling should address imprinting, recurrence risk, and reproductive options such as prenatal diagnosis or preimplantation genetic testing when a familial pathogenic variant is known (pqac-00000002, pqac-00000006) | MAXO candidates: genetic counseling; prenatal molecular diagnosis; preimplantation genetic testing | Standard clinical genetics inference anchored to imprinting mechanism; moderate |
| Animal models | Disease-relevant models include Magel2-deficient mice and Magel2 truncation rat models; they recapitulate selected behavioral, neurodevelopmental, thermoregulatory, and muscle-related phenotypes and are used for mechanistic and therapeutic studies (pqac-00000009, pqac-00000010) | model organism terms: mouse model; rat model; Magel2-deficient; truncation knock-in candidate | Animal/preclinical evidence; moderate |
| Experimental therapeutics | Oxytocin is the best-supported experimental therapeutic concept from preclinical work: early postnatal treatment improved some social/developmental phenotypes in Magel2-deficient models, but optimal window, CNS delivery, and human efficacy remain uncertain (pqac-00000009, pqac-00000010) | CHEBI candidate: oxytocin; MAXO candidate: oxytocin therapy | Animal/preclinical evidence; moderate, not established clinically |
| Clinical trials status | A search retrieved no clearly relevant SYS-specific interventional clinical trials in the available tool output, underscoring a sparse formal trial landscape (pqac-00000000) | research status concept: no SYS-specific trial captured | Trial registry search snapshot; weak-moderate |
| Explicit knowledge gaps | Major gaps include true prevalence/incidence, validated biomarkers, genotype-phenotype correlations by variant, long-term natural history, adult outcomes, standardized QoL metrics, controlled GH and oxytocin studies, and consensus diagnostic/management guidelines across centers (pqac-00000002, pqac-00000006, pqac-00000009) | research gap annotations: epidemiology unknown; biomarker validation needed; natural history study needed | Cross-source synthesis; strong as a gap statement |


*Table: This table summarizes ontology-ready, evidence-backed facts for Schaaf-Yang syndrome across identifiers, mechanisms, phenotypes, diagnostics, management, and models. It is designed as a compact knowledge-base input with explicit evidence strength and clearly marked gaps.*