| Phenotype | HPO term(s) | Frequency (Akizu 2015) | Frequency (Thomas 2014) | Onset/progression notes | Evidence citations |
|---|---|---:|---:|---|---|
| Global developmental delay / severe developmental impairment | HP:0001263 Developmental delay; HP:0011344 Severe global developmental delay | 22/22 delayed gross motor; 22/22 delayed fine motor; 22/22 delayed/absent social development | Severe intellectual disability in most; 7/7 affected with major neurodevelopmental impairment | Usually presents between birth and 1 year; early pervasive developmental impairment | (pqac-00000039, pqac-00000040, pqac-00000042) |
| Intellectual disability | HP:0001249 Intellectual disability; HP:0010864 Severe intellectual disability | Not separately enumerated in retrieved Akizu table text, but syndrome includes intellectual disability across cohort | Severe in most; 1 moderate among 7 | Early-onset, persistent cognitive disability | (pqac-00000040, pqac-00000042, pqac-00000044) |
| Speech delay / absent speech | HP:0000750 Delayed speech and language development; HP:0001344 Absent speech | 22/22 delayed or absent language | 5/7 absent or severely impaired speech | Major communication impairment from infancy/early childhood; often lifelong | (pqac-00000039, pqac-00000042, pqac-00000043) |
| Hypotonia | HP:0001252 Hypotonia | 22/22 | 6/7 | Present from infancy; often among earliest signs | (pqac-00000039, pqac-00000040, pqac-00000042) |
| Ataxia / gait abnormality / absent ambulation | HP:0001251 Ataxia; HP:0002066 Gait ataxia; HP:0002540 Inability to walk | 22/22 wide-based gait or absent gait | Ataxia in 5/6 assessed; only 1/7 achieved independent ambulation by age 3 years | Early motor delay; ambulation often absent or markedly delayed; cerebellar signs progressive | (pqac-00000039, pqac-00000040, pqac-00000042) |
| Delayed motor milestones | HP:0001270 Motor delay; HP:0002194 Delayed gross motor development | 22/22 gross motor delay | Sitting markedly delayed; only 4/7 walked with help | Childhood-onset; substantial impact on mobility and daily function | (pqac-00000039, pqac-00000042, pqac-00000043) |
| Cerebellar atrophy | HP:0001272 Cerebellar atrophy | 22/22 | 5/7 | Age-dependent; may be absent in infancy/early imaging and then become progressive | (pqac-00000039, pqac-00000040, pqac-00000042, pqac-00000043) |
| Pontine thinning | HP:0001302 Pontocerebellar hypoplasia / HP:0006829 Pontine atrophy (closest related HPO concepts) | Not specified in retrieved Akizu frequency text | 4/7 | Reported on MRI in Thomas cohort; brainstem relatively preserved compared with cerebellum in some images | (pqac-00000042, pqac-00000020) |
| Coarse facial features | HP:0000280 Coarse facial features | 22/22 | 7/7 | Distinctive gestalt supports recognition; features may become progressively coarse | (pqac-00000039, pqac-00000040, pqac-00000042) |
| Relative macrocephaly / macrocephaly | HP:0000256 Macrocephaly; HP:0011227 Relative macrocephaly | Not quantified in retrieved Akizu table text | Several individuals had OFC >97th centile; not summarized as total count in retrieved text | Relative macrocephaly noted as characteristic syndrome feature | (pqac-00000040, pqac-00000042) |
| Hearing loss (sensorineural) | HP:0000407 Sensorineural hearing impairment | 5/22 | 5/7 | Variable associated feature; not universal | (pqac-00000039, pqac-00000040, pqac-00000042) |
| Seizures / epilepsy | HP:0001250 Seizure | 8/22; about half developed seizures by age 2 years in narrative summary | Absent in original Thomas family set per syndrome description | Variable; often early childhood onset when present; reported as medically controllable in Akizu series | (pqac-00000039, pqac-00000040, pqac-00000017) |
| Nystagmus / oculomotor abnormality | HP:0000639 Nystagmus | 11/22 | Not reported as frequency in Thomas retrieved table text | Common associated neurologic sign in Akizu cohort | (pqac-00000039, pqac-00000040) |
| Autism-like / stereotyped behavior | HP:0000729 Autistic behavior; HP:0000733 Stereotypy | 12/22 autistic-like behavior | Not reported in Thomas table | Neurobehavioral manifestation in a substantial subset | (pqac-00000039) |
| Hyporeflexia / areflexia | HP:0001265 Hyporeflexia; HP:0001284 Areflexia | Reduced deep tendon reflexes in most children (narrative) | 5/6 hypo/areflexia | Peripheral neurologic involvement accompanies cerebellar syndrome | (pqac-00000040, pqac-00000042) |
| Fifth-finger brachy/camptodactyly / broad short digits | HP:0004209 Camptodactyly of finger; HP:0001182 Brachydactyly; HP:0009381 Broad finger | Kyphoscoliosis/clinodactyly 10/22 | 6/7 brachy/camptodactyly of 5th fingers; 7/7 short broad fingers/toes | Skeletal/digital anomalies are common supportive findings | (pqac-00000039, pqac-00000042) |
| Hypertrichosis | HP:0000998 Hypertrichosis | 12/22 | Not reported in Thomas table | Variable syndromic feature | (pqac-00000039) |
| Macroglossia | HP:0000158 Macroglossia | 12/22 | Not reported in Thomas table | Variable syndromic feature | (pqac-00000039) |
| Hepatosplenomegaly | HP:0001433 Hepatosplenomegaly | 5/22 | Not reported in Thomas table | Infrequent extra-neurologic feature; helped raise lysosomal-storage-disease differential in some cases | (pqac-00000039, pqac-00000041) |
| Abnormal urine oligosaccharides / glycosaminoglycans | HP:0033106 Abnormal urine oligosaccharide level; HP:0012411 Abnormal urinary glycosaminoglycan excretion | 5/22 abnormal oligosaccharides or GAG-related testing in retrieved table summary | Not reported | Laboratory abnormalities were inconsistent and lysosomal enzyme assays could be unrevealing | (pqac-00000039, pqac-00000041) |


*Table: This table maps core phenotypes of SNX14-related SCAR20/Lichtenstein-Knorr syndrome to suggested HPO terms and summarizes frequencies from the Akizu 2015 and Thomas 2014 cohorts where available. It is useful for phenotype curation, ontology annotation, and comparing syndrome-defining features across the two foundational cohorts.*