Decreased circulating IgM concentration Transient decreased circulating IgM concentration 2026-04-29T09:05:55Z https://orcid.org/0000-0003-4311-3550 https://orcid.org/0000-0002-3356-9506 PMID:37685399 transient IgM deficiency PMID:28984901 https://orcid.org/0000-0002-0418-7381 A temporary reduction in the total concentration of immunoglobulin M (IgM) in the circulation that is documented at one or more time points but subsequently normalizes on follow-up measurement. Transient decreases in circulating IgM concentration have been observed particularly in infants and young children. The distinction from persistent selective IgM deficiency requires serial measurement of serum IgM levels over time. A single low IgM value does not establish persistence, and the majority of individuals with an isolated low IgM measurement do not have persistent deficiency. https://orcid.org/0000-0003-1055-2063