Dihydropyrimidinase deficiency and congenital microvillous atrophy: coincidence or genetic relation?

We describe a boy of consanguineous parents who suffered from intractable diarrhoea due to congenital microvillous atrophy, a recessively inherited autosomal disorder. He developed severe cholestatis starting at 2 weeks of age and leading to liver cirrhosis. His psychomotor development appeared only slightly delayed. At the age of 7 months he died due to septicaemia. In addition to disturbances of electrolyte balance and renal tubular function, which could be attributed to microvillous atrophy, marked elevations of dihydrouracil and dihydrothymine as well as moderately elevated excretion of uracil and thymine in urine were repeatedly demonstrated, suggesting a disorder of pyrimidine degradation. An enzymatic defect of 5,6-dihydropyrimidine amidohydrolase (EC 3.5.2.2, dihydropyrimidinase, DHP) was demonstrated in liver biopsy. As both of these recessive disorders seem to be extremely rare, it remains speculative, whether he suffered from two independently inherited metabolic diseases or whether this represents a hitherto undescribed contiguous gene syndrome.