Anorexia nervosa is a chronic psychiatric process characterized by a restrictive disorder in alimentary habits. Hematologic alterations in the peripheral blood include cytopenias involving one or more hematopoietic lineages. Morphologic changes in the bone marrow and stereologic alterations in bone marrow adiopocytes may also be observed in anorexia nervosa. We present a 12-year-old girl who had chronic anorexia and one third of body weight loss during an 8-month period. She was apathetic and had missed several menstrual cycles. The sex maturity rating was Tanner stage IV. There was no lymphadenopathy, no hepatosplenomegaly, and no identifiable tumor mass. She was not anemic, but was found to have leukopenia, neutropenia and a low level of triiodothyronine. Sections of the bone marrow biopsy showed almost complete serous atrophy (gelatinous degeneration) of the bone marrow. In this patient, the bone marrow alteration is related to nutritional deprivation of anorexia nervosa.