BENIGN METHYLMALONIC ACIDEMIA IN A SIBSHIP WITH DISTAL RENAL TUBULAR-ACIDOSIS

Two male infants born to consanguineous parents were investigated for feeding difficulties in the Ist month of life. Both were found to have distal renal tubular acidosis (dRTA) with hypercalciuria. Nephrocalci nosis was present in the first child but not in the second. Urinary or ganic acid profile demonstrated an excess of methylmalonic acid (MMA) in both children in the absence of any other organic acid. MMA mutase activity and propionate incorporation were normal. There have been no neurological symptoms in either child. The first child has normal grow th and psychomotor development at 4 years. His brother, who also has s ignificant gastrooesophageal reflux, has failed to thrive and currentl y requires nasogastric feeding and caloric supplements to maintain wei ght along the 3rd percentile. Urinary and plasma MMA continue to be ra ised in both cases. The association of increased urinary and plasma MM A and dRTA presenting in the Ist month of life has not previously been reported and may represent a new syndrome of autosomal recessive inhe ritance.