IgM deficiency - Immunoglobulin M deficiency: Description, Causes and Risk Factors:
IgM antibodies are the largest type of antibody. They are found in the bloodstream and lymph fluid. The IgM antibodies are the first antibodies that are produced in response to an infection. They also stimulate other immune system cells to produce compounds that can destroy invading cells. IgM antibodies normally make up about 5-10% of all the antibodies in the body.
Selective immunoglobulin M deficiency (SIgMD) is a rare form of primary immunodeficiency with a reported prevalence of 0.03% to 3%. Selective IgM deficiency can be asymptomatic or present symptomatically with infections caused by encapsulated bacteria and viruses, some of which can be serious and even life-threatening. These vary from pneumonia to septicemia and meningitis.
Selective IgM deficiency is a heterogeneous disorder with no known genetic component, and may occur as a primary or a secondary condition. Primary in children may present with severe life-threatening infections, whereas in adults it is usually associated with autoimmune diseases and malignant neoplasm. Secondary selective IgM deficiency is much more common than primary selective IgM deficiency and may be seen in association with malignancy, autoimmune disease, gastrointestinal disease, and immunosuppressive treatment.
The pathogenesis of primary selective IgM deficiency is unknown. A number of defects have been reported, including intrinsic B-cell defect in plasma cell differentiation, increased T-cell suppressor activity, which may be specific to IgM isotype or isotype-nonspecific, and decreased helper T-cell activity. This suggests that selective IgM deficiency is a heterogeneous disorder, which requires further studies to elucidate the predominant mechanisms involved in its pathogenesis.
The cause of SIgM deficiency is unknown, and no clear pattern of inheritance has been suggested. The stability of the finding of selective deficiency of IgM versus progression to deficiency of other immunoglobulin isotypes, has not been well characterized.
Patients with malignant neoplasms (eg, clear cell sarcoma, Bloom syndrome, promyelocytic leukemia), autoimmune diseases (eg, rheumatoid arthritis, Hashimoto thyroiditis, systemic lupus erythematosus, autoimmune hemolytic anemia), infections (eg, Brucella), or those given immunosuppressive agents may develop secondary SIgM deficiency.
Patients with selective immunoglobulin M deficiency are susceptible to recurrent sepsis and overwhelming infection with encapsulated bacteria (eg, Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae). They may also have autoimmune disease including glomerulonephritis and osteomyelitis from which organisms are not recoverable, as well as malignancies, chronic dermatitis, diarrhea, and upper respiratory infections (UTIs).
Patients may be asymptomatic, while others may experience prolonged or life-threatening infections, especially during infancy. Recurrent infections, including, sinusitis and pneumonia, are caused by bacteria
. Patients may also experience atopic or chronic dermatitis, allergic rhinitis
(hay fever), wheezing, and/or diarrhea.
A nephelometry blood test may be performed to diagnose SIgM deficiency. The disorder is diagnosed after significantly decreased IgM are observed in the patient's blood. During the procedure, a sample of blood is taken from the patient. Anti-immunoglobulins are added to the blood sample. A medical instrument then measures the movement of particles in a substance that is caused by the interaction between immunoglobulins and anti-immunoglobulins. The test quickly and accurately measures the amount of IgM in the patient's blood.
Infections should be treated promptly with appropriate antibiotics, depending on the suspected pathogen. Empiric broad-spectrum therapy may be necessary before specific organisms are isolated. Some patients with selective IgM deficiency may also have increased susceptibility to fungal infections, so excessive use of broad spectrum antibiotics should be avoided, and antifungals should be added when appropriate. Intravenous immunoglobulin is a therapeutic consideration for patients with SIgM deficiency who have demonstrated findings of defective antigen-specific IgG responses, particularly if they lack IgG against encapsulated bacteria and have chronic or recurrent sinopulmonary infection.
Commonly prescribed antibiotics include amoxicillin (Trimox® or Biomox®), cefuroxime (Ceftin®, Kefurox®, or Zinacef®), amoxicillin (Amoxil®, Polymox®, or Trimox®), trimethoprim/sulfamethoxazole, also called TMP/SMX (Bactrim®, Cotrim®, or Septra), azithromycin (Zithromax®), clarithromycin (Biaxin®), erythromycin (Erythrocin® or Ery-Tab®), and amoxicillin and clavulanate (Augmentin®).
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.