Table 5.

Differential diagnosis of relative lymphopenia ≤21% (n = 21%–52%)

Infectious Causes

Noninfectious Causes

•CMV •HHV-6 •HHV-8 •HIV •Miliary tuberculosis •Legionnaires' disease •Typhoid fever •Q fever •Brucellosis •Malaria •Babesiosis •SARS •Influenza •Avian influenza •Swine influenza •Rocky Mountain spotted fever •Histoplasmosis •Dengue fever •Chikungunya fever •Ehrlichiosis •Parvovirus B19 •HPS •WNE •Viral hepatitis (early)

•Cytoxic drugs •Steroids •Sarcoidosis •SLE •Lymphoma •Rheumatoid arthritis •Radiation •Wiskott-Aldrich syndrome •Whipple's disease •Severe combined immunodeficiency disease (SCID) •Common variable immune deficiency (CVID) •DiGeorge's syndrome •Nezelof's syndrome •Intestinal lymphangiectasia •Ataxia telangiectasia •Constrictive pericarditis •Tricuspid regurgitation •Kawasaki's disease •Idiopathic CD4 cytopenia •Acute/chronic renal failure •Hemodialysis •Myasthenia gravis •Celiac disease •Alcoholic cirrhosis •Coronary bypass •Wegener granulomatosis •CHF •Acute pancreatitis •Carcinomas (terminal)

Abbreviations: CHF, congestive heart failure; CLL, chronic lymphocytic leukemia; EBV, Epstein-Barr virus; HCV, hepatitis C virus; HHV, human herpesvirus; HPS, hantavirus pulmonary syndrome; SARS, severe acute respiratory syndrome; SLE, systemic lupus erythematosus; WNE, West Nile encephalitis.

Adapted from Cunha CB. Infectious disease differential diagnosis. In: Cunha BA, editor. Antibiotic essentials. 9th edition. Sudbury (MA): Jones & Bartlett; 2010.