Lymphocytopenia

Lymphocytopenia, or lymphopenia, is a lower-than-normal level of lymphocytes in the peripheral blood. In adults, an absolute lymphocyte count below about 1.0 x 10^9/L is commonly used as a threshold, though reference ranges vary. The condition may reflect reduced production, increased destruction, or sequestration of lymphocytes and can involve T cells, B cells, or natural killer cells.

Causes include primary (congenital) and acquired factors. Acquired causes are common and include HIV infection, acute or chronic illnesses, malnutrition, autoimmune diseases, and medications such as systemic corticosteroids, chemotherapy, and other immunosuppressants. Bone marrow disorders, radiation therapy, splenic sequestration, and aging can contribute. In many cases the cause remains unknown.

Clinical features and evaluation: Mild cases may be asymptomatic; more severe or persistent lymphocytopenia increases susceptibility to infections, especially viral, fungal, and opportunistic infections. Evaluation starts with a complete blood count with differential, followed by lymphocyte subset analysis and testing for HIV. Additional investigations target potential underlying causes, including nutritional assessment, autoimmune serologies, and bone marrow studies when indicated.

Management and prognosis: Management depends on the cause and severity. Treatment focuses on addressing underlying conditions, vaccination where appropriate, and infection prevention. In HIV-related lymphocytopenia, antiretroviral therapy often improves lymphocyte counts. Prognosis varies with etiology and the degree of lymphocytopenia; isolated mild lymphocytopenia may have little short-term impact, while persistent severe lymphocytopenia carries higher infection risk and requires specialist evaluation.