title: [Diagnosis of lymphocytopenia].
abstract: Lymphopenia is defined as a peripheral lymphocyte count lower than 1500/mm3 in adults and 4500/mm3 in children younger than eight months of age. We propose a classification of lymphopenia according to the mechanism involved: lymphocyte production defects, including primary immune deficiencies and immune deficiencies secondary to malnutrition or zinc deprivation; excess catabolism, due to causes including radiotherapy, chemotherapy, immunosuppressive therapy, HIV infection, and systemic lupus erythematosus; abnormal lymphocyte trapping, including mainly splenomegaly, certain viral infections, septic shock, extended burns, systemic granulomatosis, and corticosteroids; other causes of lymphocytopenia, with mechanisms that remain poorly understood: ethnicity (Ethiopians), lymphoma, renal insufficiency, and idiopathic CD4 lymphocytopenia.
authors.affiliation: Service de médecine interne, Hôpital Cochin, AP-HP, université Paris-Descartes, faculté de médecine, Paris (75).
authors.forename: Alice
authors.initials: A
authors.lastname: Berezné
authors.forename: Wafaa
authors.initials: W
authors.lastname: Bono
authors.forename: Loïc
authors.initials: L
authors.lastname: Guillevin
authors.forename: Luc
authors.initials: L
authors.lastname: Mouthon
mesh_terms: D006801:Humans; D008231:Lymphopenia / Q000145:classification / Q000175:diagnosis* / Q000209:etiology