It is unknown why many patients with pernicious anaemia are satisfactorily treated with injections of hydroxocobalamin or cyanocobalamin every 1–3 months whereas others require far more frequent replacement regimens, sometimes even weekly. A substantial but inconstant fraction of an injected dose of cobalamin is excreted in the urine within 72 h of injection, with subsequent loss of variable smaller amounts. We hypothesize the existence of ‘hypercobalaminuria’, whereby increased urinary cobalamin losses constitute a currently unrecognized factor influencing treatment refractoriness in some individuals. The hypothesis is testable by comparing cobalamin urinary losses in patients needing frequent as opposed to 1–3-monthly injections of cobalamin to remain symptom-free. It implies that ‘less-responsive’ patients are likely to have significant hypercobalaminuria.

Link: https://www.sciencedirect.com/science/article/pii/S0306987725001033