Title

Clinical and Molecular Heterogeneity in Patients with the CblD Inborn Error of Cobalamin Metabolism

Authors

Isabelle R. Miousse, McGill University
David Watkins, McGill University
David Coelho, University Children's Hospital, Basel, Switzerland
Tony Rupar, University of Western Ontario
Eric A. Crombez, University of California - Los Angeles
Eric Vilain, University of California - Los Angeles
Jonathan A. Bernstein, Stanford University
Tina Cowan, Stanford University
Christopher Lee-Messer, Stanford University
Gregory M. Enns, Stanford University
Brian Fowler, University Children's Hospital, Basel, Switzerland
David S. Rosenblatt, McGill University

Document Type

Article

Publication Date

4-2009

Journal

Journal of Pediatrics

Volume

154

Issue

4

First Page

551

Last Page

556

URL with Digital Object Identifier

10.1016/j.jpeds.2008.10.043

Abstract

OBJECTIVES: To describe 3 patients with the cblD disorder, a rare inborn error of cobalamin metabolism caused by mutations in the MMADHC gene that can result in isolated homocystinuria, isolated methylmalonic aciduria, or combined homocystinuria and methylmalonic aciduria.

STUDY DESIGN: Patient clinical records were reviewed. Biochemical and somatic cell genetic studies were performed on cultured fibroblasts. Sequence analysis of the MMADHC gene was performed on patient DNA.

RESULTS: Patient 1 presented with isolated methylmalonic aciduria, patient 3 with isolated homocystinuria, and patient 2 with combined methylmalonic aciduria and homocystinuria. Studies of cultured fibroblasts confirmed decreased synthesis of adenosylcobalamin in patient 1, decreased synthesis of methylcobalamin in patient 3, and decreased synthesis of both cobalamin derivatives in patient 2. The diagnosis of cblD was established in each patient by complementation analysis. Mutations in the MMADHC gene were identified in all patients.

CONCLUSIONS: The results emphasize the heterogeneous clinical, cellular and molecular phenotype of the cblD disorder. The results of molecular analysis of the MMADHC gene are consistent with the hypothesis that mutations affecting the N terminus of the MMADHC protein are associated with methylmalonic aciduria, and mutations affecting the C terminus are associated with homocystinuria.