Isolated primary immunoglobulin M deficiency is a poorly defined

dysgammaglobulinemia Dysgammaglobulinemia is a type of immune disorder characterized by a reduction in some types of gamma globulins, resulting in heightened susceptibility to some infectious diseases where primary immunity is antibody based. It is distinguished from ...

characterized by decreased levels of

IgM Immunoglobulin M (IgM) is one of several isotypes of antibody (also known as immunoglobulin) that are produced by vertebrates. IgM is the largest antibody, and it is the first antibody to appear in the response to initial exposure to an antig ...

while levels of other immunoglobulins are normal. The immunodeficiency has been associated with some clinical disorders including recurrent infections,

atopy Atopy is the tendency to produce an exaggerated immunoglobulin E (IgE) immune response to otherwise harmless substances in the environment. Allergic diseases are clinical manifestations of such inappropriate, atopic responses. Atopy may have a ...

Bloom's syndrome Bloom syndrome (often abbreviated as BS in literature) is a rare autosome, autosomal recessive genetic disorder characterized by short stature, predisposition to the development of cancer, and genomic instability. BS is caused by mutations in the ' ...

celiac disease Coeliac disease (British English) or celiac disease (American English) is a long-term autoimmune disorder, primarily affecting the small intestine, where individuals develop intolerance to gluten, present in foods such as wheat, rye and barle ...

, systemic lupus erythematosus and malignancy, but, surprisingly, SIgMD seems to also occur in asymptomatic individuals. High incidences of recurrent upper respiratory tract infections (77%),

asthma Asthma is a long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wheezing, co ...

(47%) and

allergic rhinitis Allergic rhinitis, of which the seasonal type is called hay fever, is a type of inflammation in the nose that occurs when the immune system overreacts to allergens in the air. Signs and symptoms include a runny or stuffy nose, sneezing, red, i ...

(36%) have also been reported. SIgMD seems to be a particularly rare antibody deficiency with a reported prevalence between 0.03% (general population) and 0.1% (hospitalized patients). The cause of selective IgM deficiency remains unclear, although various mechanisms have been proposed, such as an increase in

regulatory T cell The regulatory T cells (Tregs or Treg cells), formerly known as suppressor T cells, are a subpopulation of T cells that modulate the immune system, maintain tolerance to self-antigens, and prevent autoimmune disease. Treg cells are immunosu ...

functions, defective

T helper cell The T helper cells (Th cells), also known as CD4+ cells or CD4-positive cells, are a type of T cell that play an important role in the adaptive immune system. They aid the activity of other immune cells by releasing cytokines. They are consider ...

functions and impaired terminal differentiation of

B lymphocytes B cells, also known as B lymphocytes, are a type of white blood cell of the lymphocyte subtype. They function in the humoral immunity component of the adaptive immune system. B cells produce antibody molecules which may be either secreted or ...

into IgM-secreting cells among others. In addition it was recently described that hypomorphic mutations in the B-cell receptor (BLNK & BTK) lead to selective IgM deficiency. It is however puzzling that

class switching Immunoglobulin class switching, also known as isotype switching, isotypic commutation or class-switch recombination (CSR), is a biological mechanism that changes a B cell's production of immunoglobulin from one type to another, such as from the ...

seems to happen normally (serum levels of other antibodies are normal), while dysfunctioning of IgM synthesis is expected to occur together with abnormalities in other immunoglobulins. Notwithstanding a clear pathogenesis and commonly accepted definition, a cutoff for SIgMD could be the lower limit of the serum IgM reference range, such as 43 mg/dL in adults or even 20 mg/dL.

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{{Immune disorders Predominantly antibody deficiencies Noninfectious immunodeficiency-related cutaneous conditions

See also

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