Medium chain acyl-CoA dehydrogenase (MCAD) deficiency is the commonest inherited disorder of fatty acid oxidation. Most clinically ascertained cases in Caucasian populations are caused by the point mutation K329E in MCAD gene. Aims of this study: 1) to determine the frequency of this mutation and specify the incidence of MCAD deficiency in our population, 2) to find in what rate this defect is responsible for sudden infant deaths. We managed to optimalize the DNA diagnostics of mutation K329E from blood spots and paraffin-embedded tissues of deceased children. 16 heterozygotes carriers of mutation K329E, were found in 4 066 analysed samples from southern Moravia, no homozygotes were found. The significantly low frequency of K329E carriers (1/254) suggests that, MCAD-deficient babies are born with a frequency somewhere above 1/100,000 in our population. Mutation K329E was proved only in 3% of tissues of suddenly deceased infants. The hypothesis that newborns who died from SIDS in our population suffered from MCAD deficiency was not confirmed. Against our expecta- tions MCAD deficiency belongs to less frequent metabolic diseases, with a higher molecular heterogeneity than in most European countries.

        Key words: MCAD deficiency, mutation K329E, fatty acid oxidation, SIDS.