The nature of myospherulosis of the upper respiratory tract.

A case of myospherulosis of paranasal sinuses similar in appearance to those recently seen in St. Louis, Missouri, was examined to ascertain the nature of the sac-like structures seen in this disease. The morphologic features of these formations and their positivity with stains for hemoglobin, peroxidase, and lipofuscin strongly suggest that they represent collections of erythrocytes altered by a foreign substance. This interpretation was confirmed by experimental production of these structures by the action of tetracycline ointment on a pure preparation of human erythrocytes.