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A syndromic neurodevelopmental disorder in which the cause of the disease is a variation in RNU4-2 gene and is inherited in an autosomal dominant pattern. It is characterized by moderate to severe global developmental delay/intellectual disability, speech anomalies (mostly non-verbal), hypotonia, abnormal brain MRI (reduced white matter volume, hypoplasia of the corpus callosum, ventriculomegaly, and delayed myelination), dysmorphic facial features, short stature, microcephaly, behavioral issues, seizures and feeding difficulties, as well as variable vision, gastrointestinal, endocrine, skeletal, genitourinary, cardiac, and cutaneous anomalies. It has autosomal dominant inheritance.
Data assembled from 7 of 12 sources · Last updated Sep 20, 2026, 1:22 PM UTC
Online Mendelian Inheritance in Man
European rare disease database
Features include always present findings: Motor delay, Anxiety, Delayed speech and language development, and Difficulty walking (gait disturbance) and others; and very common findings: Short attention span, Impaired toileting ability, Low muscle tone (hypotonia), and Feeding difficulties and others. 100 total HPO annotations.
Organ System | Phenotype Count | Example Features |
|---|---|---|
Brain and nerves | 26 | Encephalopathy, Cerebral palsy, Irritability |
Head and neck | 5 | Narrow palate, Thick lower lip vermilion, Facial hypotonia |
Digestive system | 4 | Gastroesophageal reflux, Constipation, Difficulty swallowing (dysphagia) |
Hormones | 4 | Small pituitary gland, Diabetes insipidus, Reduced circulating growth hormone concentration |
Eyes | 3 | Nystagmus, Blindness, Optic nerve hypoplasia |
Growth and development | 2 | Short stature, Reduced circulating growth hormone concentration |
Muscles | 2 | Low muscle tone (hypotonia), Facial hypotonia |
Arms and legs | 1 | Tapered finger |
Ears | 1 | Recurrent otitis media |
Skin | 1 | Thin nail |
Bones and joints | 1 | Weak and brittle bones (osteoporosis) |
RNU4-2 function has not been fully characterized.
Neurodevelopmental disorder with hypotonia, brain anomalies, distinctive facies, and absent language is strongly associated with mutations in the RNU4-2 gene on chromosome 12.
Genetic testing for RNU4-2 is available. Testing is considered confirmatory for diagnosis.
Phenotype severity distribution: 7 always present features, 5 very common features, 16 common features.
Estimated prevalence: <1 in 1,000,000 (VERY_RARE).
No clinical trials have been registered for neurodevelopmental disorder with hypotonia, brain anomalies, distinctive facies, and absent language.
6 publications have been identified in PubMed for neurodevelopmental disorder with hypotonia, brain anomalies, distinctive facies, and absent language. Research spans Basic Science / Preclinical (50%), Case Report / Case Series (33%), and Review / Meta-Analysis (17%).
Ajmone PF (2026). [PMID: 41681065](https://pubmed.ncbi.nlm.nih.gov/41681065/). *Am J Med Genet B Neuropsychiatr Genet*. [Case Report / Case Series]
Greene D (2026). [PMID: 41912932](https://pubmed.ncbi.nlm.nih.gov/41912932/). *Nat Genet*. [Basic Science / Preclinical]
Greene D (2025). [PMID: 40909831](https://pubmed.ncbi.nlm.nih.gov/40909831/). *medRxiv*. [Basic Science / Preclinical]
Okamoto N (2025). [PMID: 40546132](https://pubmed.ncbi.nlm.nih.gov/40546132/). *Am J Med Genet A*. [Case Report / Case Series]
Di Letto P (2025). [PMID: 41127311](https://pubmed.ncbi.nlm.nih.gov/41127311/). *Neurol Genet*. [Review / Meta-Analysis]
Jackson A (2025). [PMID: 40442284](https://pubmed.ncbi.nlm.nih.gov/40442284/). *Nat Genet*. [Basic Science / Preclinical]