How do cblC disorders differ from isolated MMA?

cblC (MMACHC gene) causes combined elevated MMA and homocysteine (both pathways affected); isolated MMA raises only methylmalonate; isolated homocystinuria raises only homocysteine.

What clinical features suggest cblC in neonates?

Early-onset cblC presents with feeding difficulties, hypotonia, developmental delay, megaloblastic anemia, and hemolytic uremic syndrome; retinal degeneration is characteristic.

What dose of hydroxocobalamin is used in cblC?

High-dose intramuscular hydroxocobalamin 1-2 mg/day initially, reducing to 1-2 mg every 1-2 days maintenance; oral preparations are less effective in severe forms.

What is MTHFR deficiency and how does it present?

Severe MTHFR deficiency (<20% activity) causes homocystinemia, hypomethioninemia, progressive neurological disease; treatment with folate, betaine, riboflavin, and methionine supplementation.

Why are both methylmalonate and homocysteine elevated in cblC?

MMACHC processes adenosylcobalamin (required for MMA metabolism) and methylcobalamin (required for homocysteine remethylation), so its deficiency blocks both pathways simultaneously.

Cobalamin Disorder Classification Calculator

Classifies cobalamin (Vitamin B12) metabolism disorders (cblA-cblG, MMA, MTHFR) using methylmalonate, homocysteine, and clinical features, guiding hydroxocobalamin dosing and supplementation.

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Frequently Asked Questions

How do cblC disorders differ from isolated MMA?

What clinical features suggest cblC in neonates?

What dose of hydroxocobalamin is used in cblC?

What is MTHFR deficiency and how does it present?

Why are both methylmalonate and homocysteine elevated in cblC?