Lymphocytopenia

A decrease in circulating lymphocytes below the reference range (adults: <1.0 × 10⁹/L; children <2 years: <3.0 × 10⁹/L), potentially impairing cell-mediated and humoral immune responses and increasing susceptibility to infections and immune dysregulation.

Causes

• Viral infections

  • Human immunodeficiency virus (HIV/AIDS)

  • Coronavirus disease 2019 (COVID-19)

  • Influenza

  • Viral hepatitis

  • Measles

• Severe infections

  • Tuberculosis

  • Sepsis

  • Pneumonia

• Medication and treatment-related causes

  • Corticosteroids

  • Chemotherapy

  • Radiation therapy

  • Immunosuppressive medications

  • Biologic agents

• Nutritional causes

  • Malnutrition

  • Zinc deficiency

  • Folate deficiency

  • Vitamin B12 deficiency

• Autoimmune and inflammatory causes

  • Systemic lupus erythematosus (SLE)

  • Rheumatoid arthritis

  • Sjögren's syndrome

  • Sarcoidosis

• Malignant causes

  • Hodgkin lymphoma

  • Non-Hodgkin lymphoma

  • Leukemia

  • Bone marrow infiltration by malignancy

• Congenital primary immunodeficiency disorders

  • Severe combined immunodeficiency (SCID)

  • DiGeorge syndrome

  • Wiskott–Aldrich syndrome

• Other causes

  • Bone marrow failure syndromes

  • Chronic kidney disease

  • Protein-losing enteropathy

  • Severe physical stress or trauma

  • Idiopathic lymphocytopenia