| Publication / cohort | Family / patients | EXT2 genotype | Key phenotype and onset | Major outcomes | Evidence caveats |
|---|---|---|---|---|---|
| Farhan et al., 2015; J Med Genet 52:666-675; PMID: 26246518; DOI: 10.1136/jmedgenet-2015-103279 | 1 Old Order Mennonite family; 4 affected siblings (3M, 1F), assessed ages reported in later summaries/thesis as ~10-19 years | Complex homozygous missense variants: p.Met87Arg and p.Arg95Cys; family segregated with recessive disease | Core SSMS phenotype: developmental delay/intellectual disability, hypotonia, seizures with onset ~2.5-5 years, macrocephaly, scoliosis/kyphosis, hypertelorism; additional renal/GI/cardiac findings in some; exostoses specifically absent (pqac-00000003, pqac-00000005, pqac-00000019, pqac-00000020) | Severe variable course: one patient died after status epilepticus at 17; one had prolonged seizure/status with hemiplegic stroke and wheelchair dependence; one had renal failure; patient fibroblasts showed reduced EXT2 protein/transcript and abolished NDST1 protein (pqac-00000014, pqac-00000019, pqac-00000020) | Most granular clinical detail available from thesis/review excerpts rather than full 2015 paper text in retrieved context; some ages differ across excerpt types because thesis followed patients longer (pqac-00000014, pqac-00000016, pqac-00000019, pqac-00000020) |
| El-Bazzal et al., 2018; Eur J Med Genet, cited in Gupta 2019; DOI reported as 10.1016/j.ejmg.2018.07.025 | 1 family; 2 brothers | Homozygous p.Ser4Leu (c.11C>T) | Severe developmental delay, seizures, feeding difficulties, microcephaly rather than macrocephaly/normal head size in later AREXT2 spectrum summaries; facial flattening/coarse features summarized in comparison table; exostoses absent in AREXT2 framing (pqac-00000012, pqac-00000013) | Expanded phenotype toward more severe neurodevelopmental disease; both boys alive at reported ages 6 and 8 in comparison table (pqac-00000012) | Direct article text was not retrieved; details come from Gupta 2019 comparison table/citation trail, so onset specifics and full systems review should be treated as second-hand summary (pqac-00000012, pqac-00000013) |
| Gentile et al., 2019; Clin Genet 95:165-171; DOI: 10.1111/cge.13458 | 1 family; 2 affected relatives/patients (F15, M21 in Gupta comparison table) | Compound heterozygous missense variants p.Asp227Asn and p.Tyr608Cys | Intellectual disability/developmental delay, seizures in one or both, macrocephaly reported as “high” head size in comparison table, facial dysmorphism; phenotype milder/variable compared with founder family; exostoses not reported as present in AREXT2 summaries (pqac-00000012, pqac-00000013) | Survived into adolescence/adulthood (15 and 21 years in comparison table), supporting variable severity and nonlethal course in some genotypes (pqac-00000012) | Full paper not retrieved; patient-level details limited to secondary table excerpt and review mentions, so seizure onset/treatment/systemic findings cannot be stated with confidence here (pqac-00000012, pqac-00000013) |
| Gupta et al., 2019; Clin Case Rep 7:632-637; DOI: 10.1002/ccr3.2010 | 1 nonconsanguineous family; proband F14 plus mildly affected fraternal twin sister; unaffected brother carried only one paternal EXT2 variant | Compound heterozygous EXT2 p.Val373Asp (c.1118T>A) and p.Thr672Met (c.2015C>T); both sisters also carried heterozygous NDST1 p.Arg454Cys VUS | Proband: developmental delay during first 2 years, regression at 27 months, autism, macrocephaly, hypertelorism, long philtrum, strabismus, GI issues, behavioral issues, seizures at ~10 years; EEG abnormal with occipital/midline spike-wave; brain MRI normal; no scoliosis/hypotonia/decreased bone density documented. Twin: milder Asperger syndrome/motor-cognitive-speech delay (pqac-00000010, pqac-00000011, pqac-00000013) | Demonstrates intrafamilial variability and possible modifier effect; low heparan sulfate measured in dried blood spot, serum, and urine in proband and unaffected parents; variants submitted to ClinVar; no exostoses reported (pqac-00000010, pqac-00000011, pqac-00000013) | EXT2 variants were classified as likely pathogenic/clinical-interest in context of emerging AREXT2 literature, but authors noted NDST1 contribution remained uncertain; unaffected parents also had low heparan sulfate, limiting biomarker specificity (pqac-00000011, pqac-00000013) |
| Sabir et al., 2022; Clin Dysmorphol 31:84-90; DOI: 10.1097/MCD.0000000000000406 | Reported as a further case / extending phenotype | Not extractable from retrieved context | Not extractable from retrieved context | Not extractable from retrieved context | Mentioned only as an unobtainable paper in search results; because no supporting details were retrieved, it is intentionally not summarized beyond bibliographic mention to avoid inventing facts (pqac-00000007) |


*Table: This table summarizes the main published human cohorts for autosomal recessive EXT2-related syndrome/SSMS, emphasizing genotype, core phenotype, outcomes, and limits of the available evidence. It is useful for quickly separating well-supported patient data from second-hand summaries and unretrieved reports.*