[Neonatal hemolytic-uremic syndrome, methylmalonic aciduria and homocystinuria caused by intracellular vitamin B 12 deficiency. Value of etiological diagnosis].

Background: A hemolytic-uremic syndrome associated with methylmalonic aciduria and homocystinuria is seen during the first weeks of life. A molecular defect in the CbIC mutation has been found. This report describes a new case with this association.

Case report: A girl, the second in this family, was born at term: her birth weight was 2,100 g, height was 47 cm and head circumference 31.5 cm. She was admitted at 32 days of age with hemolytic anemia and fragmencytosis, renal failure and thrombocytopenia. The renal failure required peritoneal dialysis followed by hemofiltration. The signs of pancytopenia of central origin and liver failure seen at that time raised the possibility of an intracellular defect of B12 metabolism. Chromatography of the amino acids and organic acids in the urine and plasma revealed homocystinemia, hypomethioninemia, homocystinuria and methylmalonic aciduria. The deficient B12 metabolism was confirmed in fibroblasts which showed deficits in both methyl and adenosyl-cobalamin synthesis. The metabolic disturbances were completely resolved after intravenous administration of hydroxy-cobalamin (2,000 micrograms per day) and folinic acid (25 mg per day) for 5 days. But the neurological abnormalities persisted, with retinitis pigmentosa and major leukodystrophic changes seen by MRI, and the infant died one month later.

Conclusion: This new case emphasizes the importance of systematically screening all cases of neonatal hemolytic-uremic syndrome for this autosomal recessive disorder.