Impairment of cellular immunity in patients with malignant external otitis.

Immunological studies were performed on 4 elderly diabetic patients with Malignant External Otitis caused by Pseudomonas aeruginosa. Impairment of cellular immunity was found. Skin tests for delayed hypersensitivity to PPD, SK-SD and Mumps antigen were negative and stimulation rates of peripheral blood lymphocytes by PHA, Con-A and PWM were depressed in all 4 patients. Serum immunoglobulins and complement levels were normal except in one case in which paraprotein IgG was found. Peripheral blood lymphoid cell markers and the neutrophil nitroblue tetrazolium (NBT) test were within normal limits in the 2 patients tested. These results indicate that cellular immune deficiency predisposes to the development of Malignant External Otitis in elderly diabetic patients.