Hemoglobin crystals in fluid specimens from confined body spaces

Hemoglobin crystals phagocytized by polymorphonuclear leukocytes were seen in cytologic preparations of a cerebrospinal fluid and two pleural fluids. In the last two cases, the crystals were seen within erythrocytes and also free in the background. Intraerythrocytic crystallization of hemoglobin is the result of polymerization of the hemoglobin molecules; it occurs in peripheral blood in certain hemoglobinopathies, being more pronounced in hemoglobin C disease. In our three cases, in which the crystallization occurred not in peripheral blood but in fluids of confined body spaces, there was no clinical evidence of hemoglobinopathy and blood hemoglobin electrophoresis performed in one of the cases revealed normal hemoglobin. Under laboratory conditions, we produced intraerythrocytic crystallization of hemoglobin in hemorrhagic pleural fluid specimens by subjecting them to agents that induced decreased oxygen concentration and osmotic dehydration of the cells. We suggest that similar processes operative in fluid accumulated in confined body spaces produce crystallization of the hemoglobin of extravasated red blood cells in the absence of hemoglobinopathy.