Background. Homocystinuria due to cystathionine b-synthase deficiency is an autosomal recessive disorder of methionine metabolism. It manifests with vascular, central nervous system and connective tissue disturbances, and phenotypically resembles Marfan’s syndrome. We analysed the clinical course of homocystinuria in Czech and Slovak patients. Methods and Results. The group of homocystinuric patients consisted of 19 individuals (12 males and 7 females) aged 5-32 years (average age 18 years), who were diagnosed between 1980 and 1999. The overall incidence of homocystinuria in the Czech and Slovak Republics was 1:287,000. The proportion of pyridoxine-responsive patients was 47 %. The average follow-up period was 10 years (range 1 month to 19 years). The prevalence of the individual signs in the group was as follows: lens dislocation - 95 % of patients, progressive myopia - 79 %, marfanoid habitus - 74 %, kyfoscoliosis - 68 %, osteoporosis - 63 %, psychomotor retardation - 58 %, other neurologic symptomatology - 58 % and tromboembolism - 21 %. The average delay between the first sign of the disease and the time when the diagnosis was made was 4 years (range 1 to 14 years). At the time of diagnosis the average levels of metabolites in plasma were as follows: total homocysteine 348 mmol/l (range 211-536), free homocystine 70 mmol/l (range 0-203) and methionine 359 mmol/l (range 75-937). Conclusions. Both the clinical course of homocystinuria due to the cystathionine b-synthase deficiency and its incidence in the Czech and Slovak Republics are similar to those in other populations. Since homocystinuria is a treatable disease, it should be included in the differential diagnosis of Marfan’s syndrome, tromboembolism and severe psychomotor retardation.

        Key words: homocystinuria, homocysteine, cystathionine b-synthase, lens ectopia, psychomotor retardation,