Selective IgM deficiency

Other Names: Selective immunoglobulin M deficiency; SIgMD

Selective IgM deficiency (SIgMD) is a rare immune disorder in which a person has no immunoglobulin M (IgM) antibodies, or too little IgM, with normal levels of IgG and IgA antibodies. IgM is the first antibody the immune system makes to fight a new infection. SIgMD can occur in infants, children, or adults. The disorder may occur as a primary disorder (on its own) or more commonly, as a secondary disorder (associated with another underlying disease or condition). SIgMD may occur in association with some cancers, autoimmune diseases, allergic diseases, and gastrointestinal diseases. Therefore, when a person does not have enough IgM, the body may have difficulty fighting infections.

Epidemiology

There is limited data regarding the prevalence of selective IgM deficiency (SIgMD) since there have not been any large-scale studies done. Estimates of prevalence appear to vary depending on specific populations studied and have ranged from 0.03% to 3.8%. According to these estimates, this means SIgMD may occur in anywhere from 3 to 380 per ten thousand people.

Cause

The underlying cause of selective IgM deficiency (SIgMD) is not yet known. Several factors may play a role in causing SIgMD. While some familial cases have been reported, no specific genes known to cause SIgMD have been found. SIgMD has been reported in people with various chromosome abnormalities, and most commonly in one that causes a chromosome disorder called 22q11.2 deletion syndrome. More studies are needed to learn more about the possible causes of SIgMD.

Signs and symptoms

Symptoms of selective IgM deficiency (SIgMD) may vary from person to person. Some people do not have any symptoms and are diagnosed by chance while being evaluated for another health problem.

Others may experience mild to severe symptoms depending on the degree of the deficiency. Whether a person has primary or secondary SIgMD (associated with another underlying condition) also plays a role in the types of symptoms a person has, as they may also have symptoms of their underlying condition. Most people with SIgMD, especially infants, have repeated bacterial and viral infections. Common infections in people with SIgMD include ear infections, sinus infections (sinusitis), bronchitis, and pneumonia. Some of these infections can result in sepsis, which can be life-threatening. Other types of infections that have been reported include smallpox and widespread molluscum contagiosum (a common skin condition in children). Children with SIgMD who are sick often may have failure to thrive and malnutrition. Some people with SIgMD have skin rashes, wheezing, or diarrhea.

People with secondary SIgMD usually have too little IgM, rather than none at all. For this reason, their symptoms of SIgMD usually are more mild and may go away if the associated underlying condition improves. Conditions that have been reported in association with SIgMD include:

• Cancers such as multiple myeloma, clear cell sarcoma, and lymphocytic leukemias.
• Blood disorders such as monoclonal gammopathies and immune thrombocytopenia.
• Autoimmune diseases such as lupus, rheumatoid arthritis, celiac disease, Crohn's disease, and Hashimoto disease.

Diagnosis

A definitive diagnosis of SIGMD, especially in children, should be established after follow-up for months to a year as in few undocumented cases serum IgM levels have normalized, and after excluding any known cause of secondary SIGMD including drug (e.g., Clozapine) induced IgM deficiency.

Treatment

Treatment for selective IgM deficiency (SIgMD) varies because some people do not have symptoms, while others are at risk for serious infections. In general, fevers and infections should be evaluated and treated as soon as possible, especially if they seem to be getting worse. People with no symptoms may not need specific treatment.

Measures should be taken to prevent infections whenever possible. Measures that have been recommended include:

• Having all recommended vaccinations.
• Aggressive treatment of allergies such as asthma and allergic rhinitis (nasal allergies).
• Prophylactic antibiotics for people who continue to get sick often.
• Immune globulin therapy (IVIG) - several researchers have reported a reduction in frequency and severity of infections in people with SIgMD treated with IVIG.
• People with SIgMD who experience new or different symptoms should be evaluated for an associated underlying disease or condition. Symptoms of SIgMD may improve or go away if an associated disorder is treated or improves.

NIH genetic and rare disease info

• NIH info on Selective IgM deficiency

Selective IgM deficiency is a rare disease.

Selective IgM deficiency Resources
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