A boy, aged 2 years 5 months, with microcephaly, large anterior fontanelle, delayed psychomotor development, micropenis, and anomalies of thumbs and halluces is reported from the Department of Medical Genetics, Belfast City Hospital, Northern Ireland. From 9 months of age, he had generalized clonic convulsions, and at 18 months he developed minor seizures. An EEG at 13 months showed prominent delta activity and runs of low voltage fast, but no hypsarryhthmia or other seizure patterns. He was never able to sit and he had no speech. Muscle tone was increased, reflexes were hyperactive, and plantar responses extensor. Eye movements were roving. Fundi were normal. Head circumference was normal (50th centile) at birth and fell to below the 2nd centile within a year. Chromosome analysis showed a 46, XY karyotype. Renal ultrasound revealed an absent left kidney. CT of head at 22 months showed enlargement of all ventricles and cisterns and hypoplasia of the vermis. At 2 years 9 months he became comatose and he died at 3 years. Autopsy was refused. A maternal aunt had short broad thumbs, but no other congenital or genetic disorders were found in the family. Using the criteria microcephaly, short thumbs, micropenis, and mental retardation, the London Dysmorphology Database selected only Wiedemann’s syndrome in diagnosis. Smith-Lemli-Opitz syndrome was also considered. [1]