Aminoacidopathies and organic acidurias in Tunisia: a retrospective survey over 23 years

Abstract

Background: Inborn errors of metabolism are neglected in developing countries because they are not as common as infectious and nutritional disorders. In Tunisia, no information is available on the incidence and epidemiological features of these inherited metabolic diseases.

Aims: To precise the profile of aminoacidopathies other than phenylketonuria and organic acidurias and to estimate their incidences in Tunisia.

Methods: Between 1987 and 2009, our laboratory received 13171 requests for analysis of patients with symptoms suggestive of inborn errors of metabolism. For these cases, ion exchange chromatography of free amino acids was performed on amino acids analyser. Urinary organic acids profiles were determined by gas chromatography-mass spectrometry.

Results: Abnormal cases were 370 (2.8%), divided into 212 cases of aminoacidopathies (57.3%) and 158 cases of organic acidurias (42.7%). The most frequent aminoacidopathies, were maple syrup disease (32.5%), tyrosinemia type I (28.8%) and nonketotic hyperglycinemia (16%). Methylmalonic aciduria (33.5%), propionic aciduria (18.4%) and 2-hyrdoxy glutaric aciduria (10.8%) were the most frequent organic acidurias. The incidences were calculated using the Hardy-Weinberg formula and were estimated at 1/13716 for maple syrup disease, 1/14804 for tyrosinemia type I, 1/16144 for methylmalonic aciduria and 1/23176 for propionic aciduria.

Conclusion: Aminoacidopathies and organic acidurias turned out to be highly frequent in Tunisia, mainly because of a high rate of consanguinity. We believe that they are underestimated. To improve their diagnosis, it is necessary to have available sophisticated equipment which would allow early treatment of patients.