A person taking an oral sulfonamide is found to have a markedly decreased peripheral blood neutrophil count, but the numbers of platelets and erythrocytes are normal. If the peripheral neutropenia is the result of antineutrophil antibodies being produced in response to taking the sulfonamide, then this patient would be expected to have
Decreased numbers of neutrophils in the peripheral blood (neutropenia) may be due to decreased production of neutrophils in the bone marrow or to increased peripheral destruction of neutrophils. Decreased production may be caused by megaloblastic anemia, ceain drugs, or stem cell defects such as aplastic anemia, leukemias, or lymphomas. Drug-induced destruction of neutrophil precursors is the most common cause of peripheral neutropenia. With all of these different causes of decreased neutrophil production, the bone marrow is hypoplastic and there is a decrease in the number of granulocytic precursors. Some causes of neutropenia also cause a decrease in the numbers of platelets and erythrocytes (pancytopenia). In contrast to decreased production, neutropenia secondary to peripheral destruction causes a hyperplasia of the bone marrow, with an increase in the number of granulocytic precursors. Causes of increased destruction of neutrophils include sequestration in the spleen due to hypersplenism (not splenic atrophy), increased utilization, such as with overwhelming infections, and immunologically mediated destruction (immune destruction). Causes of immune destruction include Felty's syndrome and ceain drug reactions, such as to aminopyrine and some sulfonamides. Drugs may cause decreased production or increased destruction of neutrophils. In the latter, antibodies are formed against neutrophils, and then these cells are destroyed peripherally. Felty's syndrome refers to the combination of rheumatoid ahritis, splenomegaly, and neutropenia. A significant number of patients with Felty's syndrome have a monoclonal proliferation of CD8 large granular lymphocytes, unrelated to drug use. Reference: Robbins & Cotran Pathologic Basis of Disease, 9edition.
An atrophic spleen
Decreased vitamin B12 levels
Hypoplasia of the bone marrow myeloid series
Hyperplasia of the bone marrow myeloid series
miscellaneous