The Lesch-Nyhan syndrome is an unusual disease. It combines neurological disorders, behavioural disturbances, metabolic changes and haematological symptoms. The syndrome is caused by an X-chromosomal transmitted enzyme deficiency of the 'salvage pathway' in purine metabolism. The hitherto unexplained pathogenesis was the reason for investigations into metabolism and morphology of the blood cells of a patient suffering from the syndrome. Along with the defect in guanine nucleotide resynthesis there was a defect of microtubules in platelets and a sphaerocytosis in red cells, which could be the result of a disassembly of structural proteins. The development and maintenance of the highly heteromorphic structure of nerve cells and the neuronal function including axonal transport of cell organelles and transmitters is dependent on microtubules. Thus a disassembly of microtubules could be the mechanism in the pathogenesis of this complex syndrome.