We report a series of eight patients with the Say/Barber/Biesecker/Young-Simpson 
(SBBYS) type of Ohdo syndrome, which is the largest cohort described to date. We 
expand on the type, frequency and severity of the clinical characteristics in 
this condition; comment on the natural history of Ohdo syndrome and further 
refine previously published diagnostic criteria. Cytogenetic investigations and 
microarray CGH analysis undertaken in this cohort of patients failed to identify 
a chromosomal aetiology. It remains possible that this rare condition is 
heterogeneous and therefore caution must be undertaken during counselling until 
the underlying genetic mechanism(s) is (are) identified.