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Methylmalonic acidemia with homocystinuria, type cblD
cblD type methylmalonic acidemia with homocystinuria is a form of methylmalonic acidemia with homocystinuria (see this term), an inborn error of vitamin B12 (cobalamin) metabolism characterized by variable biochemical, neurological and hematological manifestations.
ORPHA:79283Classification level: Subtype of disorder
- CblD defect
- Cobalamin D defect
- Combined defect in adenosylcobalamin and methylcobalamin synthesis, type cblD
- Methylmalonic aciduria with homocystinuria, type cblD
- Prevalence: <1 / 1 000 000
- Inheritance: Autosomal recessive
- Age of onset: All ages
- ICD-10: E72.1
- OMIM: 277410
- UMLS: C1848552
- MeSH: -
- GARD: 3582
- MedDRA: -
To date, 17 cases of cblD have been reported (6 classic cblD, 5 cblDv1 and 6 cblDv2).
Three different presentations have been described: the classic form with combined methylmalonic aciduria and homocystinuria; cblD variant 1 (cblDv1) with isolated homocystinuria; and cblD variant 2 (cblDv2) with isolated methylmalonic aciduria. Clinical presentation is extremely variable. The disorder can present from early infancy to late childhood. Presenting signs are variable depending on which aspect(s) of cobalamin metabolism are affected and can include developmental delay, severe learning difficulties, seizures, movement and gait abnormalities, behavioral problems and signs of megaloblastic anemia (pallor, fatigue, anorexia).
The causal gene for cblD is MMADHC (2q23.2) and the disorder is transmitted in an autosomal recessive manner.
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