A form of dominantly inherited olivopontocerebellar atrophy (OPCA) occurs commonly in persons of Spanish ancestry in northeastern Cuba. Its prevalence in the Province of Holguin is 41 per 100,000, a figure much higher than that found in western Cuba or in other parts of the world. The high prevalence is probably the result of a founder effect, but might be due to an interaction between a mutant gene and an unidentified environmental neurotoxin. We describe the clinical features of this disorder, and the neuropathological abnormalities in 7 autopsied patients. In addition, we report biochemical findings in plasma, cerebrospinal fluid (CSF) and urine obtained from 10 living OPCA patients. Quantitation of amino acids in fasting plasma showed a number of differences between the Cuban patients and healthy Canadian controls, but these are likely to have been caused by dietary differences. Amino acid concentrations in the CSF of the Cuban OPCA patients were similar to those of healthy Cuban controls, except for a decreased concentration of ethanolamine. Mean concentrations of dopamine metabolites were significantly low in the CSF of the OPCA patients, corresponding to neuronal depletion observed in the substantia nigra of autopsied cases. Examination of the patients' urines provided no evidence that either cyanide or 3-acetylpyridine is involved in causing this form of OPCA.
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