Ohdo syndrome—SBBYS variant
Definition An über rare—30 cases in the world literature—multi-system, possibly autosomal recessive, malformation complex (OMIM:603736) characterised by microcephaly, distinct facies, severe blepharophimosis, an immobile mask-like face, a bulbous nasal tip, and a small mouth with a thin upper lip. It presents in infancy with severe hypotonia and feeding problems. Associated skeletal problems include joint laxity, abnormally long thumbs and great toes, and dislocated or hypoplastic patellae. Cardiac defects are present in about 50% of cases, as are dental anomalies including small and pointed teeth. Affected individuals may have defects in thyroid structure or function. Ohdo syndrome-SBBYSS is usually associated with severe mental retardation, delayed developmental milestones, significantly impaired speech, hearing impairment, abnormal ears and growth retardation. Male patients may have cryptorchidism and scrotal hypoplasia.
Molecular pathology Defects in KAT6B, which encodes a histone acetyltransferase that, depending on the context, up- or down-regulates transcription, cause Ohdo syndrome.
Synonyms Blepharophimosis-intellectual deficit syndrome—Say-Barber/ Biesecker/Young-Simpson type, Ohdo-Madokoro-Sonoda syndrome, Young-Simpson syndrome