Résumé
Neutropenia is defined as a neutrophil count lower than 1.5g/L, with categorization as mild, moderate, or severe when the count is 1.5-1g/L, 1-0.5g/L, or<0.5g/L, respectively. The main complication is infection, whose risk increases with the depth and duration of the neutropenia. Comprehensive etiological investigations are mandatory to determine the best treatment strategy. Constitutional neutropenia is rarely seen in everyday rheumatology practice. It predominantly affects patients of African descent and is usually moderate and well tolerated. Congenital neutropenia due to genetic abnormalities is severe and chiefly seen in the pediatric population. Most cases of neutropenia in patients with rheumatoid arthritis (RA) are acquired. Medications are the most common causes, making detailed history-taking crucial. Many medications used to treat RA can induce neutropenia. Folic acid deficiency should be sought routinely in patients taking methotrexate. A less common cause of neutropenia is an RA-related autoimmune reaction. Splenomegaly suggests Felty's syndrome, which is accompanied with large granular lymphocytic (LGL) leukemia in 40% of cases. The treatment depends on the depth of the neutropenia and findings from the etiological workup. A neutrophil count below 0.5g/L, a fever, and the presence of clinical signs indicate a life-threatening condition requiring emergent treatment. In other patients, the first step is immediate discontinuation of any possibly involved drugs, simultaneously with the etiological workup.