MOLYBDENUM COFACTOR DEFICIENCY-PHENOTYPIC VARIABILITY IN A FAMILY WITH A LATE-ONSET VARIANT

In a family with molybdenum cofactor deficiency, the onset in the inde x case was delayed until 1 year of age, when the patient presented wit h an episode of lethargy and inconsolable crying culminating in a seiz ure. By lr months she showed mild motor delay, regression in language skills, and feeding difficulties. Progressive global deterioration fol lowed, associated with sustained irritability, dystonic posturing, and further seizures, before her condition subsequently plateaued, Low pl asma uric acid, raised urinary xanthine and hypoxanthine, and positive urinary sulphite were found, which, coupled with assay of sulphite ox idase activity in cultured fibroblasts, confirmed the diagnosis. A sib ling had isolated lens dislocation and an identical biochemical profil e, MRI in both children was strikingly abnormal, Molybdenum cofactor d eficiency may present as a late-onset variant with considerable phenot ypic variability.