Selective deficiency of immunoglobulin M [IgM]

This code signifies a primary immunodeficiency characterized by abnormally low levels of immunoglobulin M (IgM) in the blood, while other immunoglobulin classes (IgG, IgA) are within normal ranges. Patients with this condition are often susceptible to recurrent bacterial infections, particularly those caused by encapsulated bacteria.

Use this code when documentation explicitly states a diagnosis of selective IgM deficiency, typically confirmed by laboratory findings showing isolated low IgM levels. This diagnosis is often made after investigating recurrent infections or a family history of immunodeficiency.

• Ensure documentation specifies "selective" IgM deficiency; do not use for panhypogammaglobulinemia or other combined immunodeficiencies.
• Distinguish from transient hypogammaglobulinemia of infancy, which has a different code.
• Code any associated infections or complications separately and sequence appropriately.