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X-linked intellectual disability, Shashi type is characterized by moderate intellectual deficit, obesity, macroorchidism and a characteristic facies (large ears, a prominent lower lip and puffy eyelids). It has been described in nine boys from two families. Transmission is X-linked and the causative gene has been localized to the q21.3-q27 region of the X chromosome.
Features include always present findings: Moderate intellectual disability, Macroorchidism, Blepharophimosis, and Narrow palpebral fissure and others; and very common findings: Coarse facial features, Everted lower lip vermilion, Delayed speech and language development, and Palpebral edema. 16 total HPO annotations.
Organ System | Phenotype Count | Example Features |
|---|---|---|
Brain and nerves | 3 | Moderate intellectual disability, Delayed speech and language development, Seizure |
Head and neck | 3 | Coarse facial features, Thick lower lip vermilion, Everted lower lip vermilion |
Ears | 1 | Bilateral sensorineural hearing impairment |
RBMX function has not been fully characterized.
Syndromic X-linked intellectual disability Shashi type is associated with mutations in the RBMX gene on chromosome X.
Genetic testing for RBMX is available. Testing is considered confirmatory for diagnosis.
Phenotype severity distribution: 10 always present features, 4 very common features, 1 common feature.
Estimated prevalence: <1 in 1,000,000 (VERY_RARE).
No clinical trials have been registered for syndromic X-linked intellectual disability Shashi type.
2 publications have been identified in PubMed for syndromic X-linked intellectual disability Shashi type. Research spans Review / Meta-Analysis (50%) and Epidemiology / Natural History (50%).
Iype M (2025). [PMID: 40445728](https://pubmed.ncbi.nlm.nih.gov/40445728/). *Annals of Indian Academy of Neurology*. [Epidemiology / Natural History]
Tilliole P (2024). [PMID: 39086926](https://pubmed.ncbi.nlm.nih.gov/39086926/). *Frontiers in molecular neuroscience*. [Review / Meta-Analysis]
Data assembled from 6 of 12 sources · Last updated Sep 20, 2026, 11:13 AM UTC
Online Mendelian Inheritance in Man
European rare disease database
Genetic and Rare Diseases Info Center