Treatment of Hemolytic-Uremic Syndrome with Elevated Plasma Total Homocysteine and MMACHC Gene Mutation
A subset of hemolytic-uremic syndrome (HUS) is caused by an inherited defect in intracellular cobalamin metabolism rather than the more common complement-mediated or Shiga-toxin-associated pathways. Recognising this distinction is critical because the treatment approach is fundamentally different.
Clinical Scenario
HUS presenting with markedly elevated plasma total homocysteine (> 50–100 μM/l, confirmed by chromatography or immunoassay) alongside normal serum vitamin B12 and folate. Genetic evaluation reveals a homozygous or compound heterozygous mutation in the MMACHC gene, consistent with probable cblC deficiency.
Treatment Approach
Prompt initiation of parenteral hydroxycobalamin is the cornerstone of management in this setting, combined with oral metabolic co-therapies targeting the homocysteine pathway.
Full regimen details — dosing, frequency, and complete sequencing — are available in the structured protocol below →
Treatment Target
The primary clinical goal is reduction of total plasma homocysteine to < 40–60 μM/L.
References
DOI: 10.1007/s00467-019-04233-7
- HUS and elevated plasma total homocysteine level (> 50–100 μM/l by chromatography, immunoassay) with normal levels of vitamin B12 and folate.
- Homozygous or compound heterozygous mutation in the MMACHC gene in a patient with probable cblC deficiency.
- We recommend that patients with probable or confirmed cblC deficiency should receive prompt therapy with parenteral hydroxycobalamin, oral betaine and folic acid.
- Patients respond to therapy with parenteral hydroxycobalamin (1 mg daily) to lower homocysteine levels < 40–60 μM/L; cyanocobalamin is not effective.
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