Classical methylmalonic acidemia is a metabolic inborn error with methylmalonic acid accumulation due to the methylmalonil-CoA mutase enzyme deficiency. It has two clinical forms as fatal neonatal and benign infantile forms. Although it is typically asymptomatic in infancy, lethargy, vomiting, hypotonia and failure to thrive may be encountered in the situations of increased catabolic state. In this article a case who had previously been diagnosed to have distal renal tubular acidosis at the age of 23 months, and however could only be detected to have methylmalonic acidemia later at the age of 5 years is presented. We emphasize that methylmalonic acidemia should be considered in the secondary causes of distal renal tubular acidosis, and both urine and serum specimens should be analyzed together to diagnose the metabolic inborn errors.
Keywords: Tandem mass spectrophotometry, distal renal tubular acidosis, carnitine, classical methylmalonic acidemia, methylmalonil-CoA mutase
