Non-syndromic agammaglobulinemia

Non-syndromic agammaglobulinemia is a primary immunodeficiency disorder characterized by a severe deficiency or complete absence of immunoglobulins (antibodies) in the blood, without the additional non-immunological features seen in syndromic forms. The condition results from a failure of B-lymphocyte development, leading to profoundly reduced or absent circulating B cells and consequently very low or undetectable levels of all immunoglobulin classes (IgG, IgA, IgM, IgE). The immune system is primarily affected, leaving patients highly susceptible to recurrent and severe bacterial infections. The most common form is X-linked agammaglobulinemia (XLA), also known as Bruton agammaglobulinemia, caused by mutations in the BTK (Bruton tyrosine kinase) gene. Autosomal recessive forms also exist, caused by mutations in genes essential for B-cell development, including IGHM (mu heavy chain), IGLL1 (lambda5/14.1), CD79A, CD79B, BLNK, and PIK3R1. Patients typically present in infancy or early childhood, after maternal antibodies wane, with recurrent sinopulmonary infections (pneumonia, sinusitis, otitis media), gastrointestinal infections, and sometimes sepsis, meningitis, or septic arthritis. Common bacterial pathogens include Streptococcus pneumoniae and Haemophilus influenzae. Patients may also be vulnerable to enteroviral infections, which can cause chronic meningoencephalitis. The mainstay of treatment is lifelong immunoglobulin replacement therapy (IgRT), administered intravenously (IVIG) or subcutaneously (SCIG), which significantly reduces the frequency and severity of infections and improves quality of life. Prompt and aggressive treatment of breakthrough infections with appropriate antibiotics is also essential. With early diagnosis and consistent immunoglobulin replacement, many patients can lead relatively normal lives, though long-term complications such as chronic lung disease (bronchiectasis) may develop if treatment is delayed or inadequate. Hematopoietic stem cell transplantation has been explored in some cases, and gene therapy research is ongoing.

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