From hypertransaminasemia to mucopolysaccharidosis IIIA

Mucopolysaccharidosis type III (MPS III; Sanfilippo syndrome) is a metabolic disorder characterized by the deficiency of a lysosomal enzyme catalyzing the catabolic pathway of heparan sulphate. MPS III presents with progressive mental deterioration, speech delay and behavioural problems with subtle somatic features, which can often lead to misdiagnosis with idiopathic developmental/speech delay, attention deficit/hyperactivity disorder or autism. We report a case of a 5-year-old boy with developmental delay and behaviour problems admitted to the Department of Paediatrics due to chronic hypertransaminasemia. The patient developed normally until the age of 2 years when he was referred to a paediatric neurologist for suspected motor and speech delay. Liver function tests were unexpectedly found elevated at the age of 3.5 years. Physical examination revealed obesity, mildly coarse facial features and stocky hands. He showed mental retardation and mild motor delay. The clinical picture strongly suggested mucopolysaccharidosis. The diagnosis of MPS IIIA was confirmed by decreased activity of heparan N-sulfatase in leucocytes.

We strongly recommend screening for MPS III in children with severe behavioural abnormalities with hyperactivity, psychomotor or speech deterioration and failure to achieve early developmental milestones particularly with facial dysmorphism.