Cobalamin C defect presenting as severe neonatal hyperammonemia.

[homocystinuria without methylmalonic aciduria]

Cobalamin C (Cbl-C ) defect is the most common inborn error of cobalamin metabolism which causes a block in the pathway responsible for the synthesis of its two metabolically active forms methyl- and adenosylcobalamin . Cbl-C defect causes the accumulation of methylmalonic acid and homocysteine and decreased methionine synthesis . The clinical presentation of patients with early -onset Cbl-C defect , characterized by a multisystem disease with severe neurological , ocular , hematological , renal , gastrointestinal , cardiac , and pulmonary manifestations , differs considerably from what observed in the "classical " form of methylmalonic aciduria caused by defect of methylmalonyl-CoA mutase . This last condition is in most cases dominated in the neonatal period by a metabolic encephalopathy "intoxication type " with severe hyperammonemia and ketoacidosis . We report a Cbl-C defect patient presenting a neonatal encephalopathy with severe hyperammonemia and ketoacidosis who was successfully treated with peritoneal dialysis .To the best of our knowledge , there are no reported cases of Cbl-C defect showing an acute presentation resembling a classical methylmalonic aciduria . This observation enlarges the spectrum of inherited diseases to be considered in the differential diagnosis of neonatal hyperammonemia .

Diseases
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Diseases presenting "differs considerably from what observed in the" symptom

homocystinuria without methylmalonic aciduria

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