Introduction: Methylmalonic acidemias (MMA) are a heterogeneous group of inborn errors of branched-chain amino acids and of other propiogenic substrates metabolism, which are characterized by the accumulation of methylmalonic acid in many body fluids. The disease is caused by a defect of the enzyme methylmalonil-CoA mutase or by one of the defects in the metabolism of its cofactor, cobalamin (B12). This study aims to describe the evolution of 13 patients with MMA in Brazil, with emphasis on long-term outcome.

Methods: Retrospective observational study was performed in Neurometabolic Diseases outpatient of HCFMUSP Pediatric Neurology Department, assessing demographics features, age at diagnosis, clinical manifestations, exams results, treatment and complications.

Results: The mean follow-up time was 4 years (5m-12y). Median age at diagnosis was 25 months, which was 12 months for B12 non responsive forms and 31 months for responsive forms. Recurrent vomiting were present in 92% of the sample; hypotonia and development delay in 100% of vitamin B12 non responders and combined with homocystinuria forms. The median values of plasma methylmalonic acid was 464,5 in vitamin B12 responders patients, 1218,9 in vitamin B12 non responders and 1337 in combined with homocystinuria forms.

Conclusion/Discussion: The diagnosis in done lazily in Brazil. The vitamin B12 non responders patients showed earlier onset of symptoms. In non responders and combined with homocystinuria cases, development delay was more frequent than in cobalamin responders.