This MMACHC gene variant was detected in a case report of 20 year-old male adult-onset Eculizumab-resistant HUS associated with cobalamin C deficiency as part of a compound heterozygosity of 2 known cobalamin C deficiency-causative mutations (c.271dupA and c.389A>G).[17–19] It is highly improbable that a single missense variant c.389A > G of MMACHC gene caused aHUS in the current case report due to the heterozygosity and absence of another compound missense mutation in MMACHC. The gene discussed is MMACHC; the disease is hemolytic-uremic syndrome.