Treatable Intellectual Disability

Cobalamin C Deficiency

DIAGNOSIS

Gene
MMACHC (AR)

Diagnostic Test
Plasma Total Homocysteine, Urine Organic Acids

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SIGNS & SYMPTOMS

Neurological
Psychosis/depression, stroke, ataxia, dystonia, spasticity)

Non-Neurological
Retinitis pigmentosa, cardiomyopathy, atypical HUS, macrocytic anemia, pancytopenia

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THERAPY

Treatment
Hydroxycobalamin

Level of Evidence
4

Clinical Practice
Standard of Care

Treatment Effect
Prevents metabolic decompensation; stabilizes clinical deterioration; improves systemic manifestations


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Cobalamin C Deficiency

CblC deficiency results in both deficiency of Adenosylcobalamin (which is cofactor for MethylmalonylCo-A Mutase) and of Methylcobalamin (which is cofactor for methionine synthase). Thus the biochemical hallmark for CblC deficiency is combined methylmalonic acidemia and homocystinemia. The age of initial presentation of CblC ranges from (1) newborns who can be small for gestational age (SGA) and have microcephaly; to (2) infants who can have poor feeding, failure to thrive, poor head growth, cytopenias (including megaloblastic anemia), global developmental delay, encephalopathy, and neurologic signs such as hypotonia and seizures; and to (3) young adults/adults who can have confusion, other mental status changes, cognitive decline, and megaloblastic anemia. (Source: GeneReviews)

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