Agammaglobulinemia

Agammaglobulinemia (Orphanet code 183669) is a group of rare primary immunodeficiency disorders characterized by a severe deficiency or near-complete absence of all classes of immunoglobulins (antibodies) in the blood, resulting from a failure of B-lymphocyte development or function. This category encompasses several genetic forms, including X-linked agammaglobulinemia (XLA, also known as Bruton agammaglobulinemia, caused by mutations in the BTK gene) and autosomal recessive forms caused by mutations in genes essential for B-cell maturation such as IGHM, IGLL1, CD79A, CD79B, BLNK, and PIK3R1, among others. The immune system is primarily affected, as the profound lack of circulating antibodies leaves patients highly susceptible to recurrent and severe bacterial infections, particularly of the respiratory tract (sinusitis, pneumonia, bronchitis), gastrointestinal tract, skin, and joints. Infections typically begin in early childhood, often after maternal antibodies wane around 6 to 12 months of age. Patients are especially vulnerable to encapsulated bacteria such as Streptococcus pneumoniae and Haemophilus influenzae. Chronic lung disease (bronchiectasis) can develop if infections are inadequately treated. Some patients may also develop enteroviral infections, including chronic meningoencephalitis, which can be life-threatening. Physical examination may reveal absent or very small tonsils and lymph nodes due to the lack of B-cell-containing lymphoid tissue. The cornerstone of treatment is lifelong immunoglobulin replacement therapy (IgRT), administered either intravenously (IVIG) or subcutaneously (SCIG), which provides passive antibody protection and significantly reduces the frequency and severity of infections. Prompt and aggressive treatment of breakthrough infections with appropriate antibiotics is also essential. With early diagnosis and consistent immunoglobulin replacement, patients can have a substantially improved quality of life and life expectancy, though vigilance for complications such as chronic lung disease and enteroviral infections remains important. Hematopoietic stem cell transplantation has been explored in select cases but is not standard therapy. Genetic counseling is recommended for affected families.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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