Malignant otitis externa is a necrotising infection of the external ear canal which may spread to include the mastoid and petrous parts of the temporal bone, leading to skull base osteomyelitis. It is almost exclusively caused by infection with Pseudomonas aeruginosa, and usually occurs in elderly non-insulin-dependent diabetic patients. However isolated cases have been reported in a small number of non-diabetic patients, particularly in children who are immunocompromised due to malignancy, malnutrition and severe anaemia. In 1984 a case of malignant otitis externa was reported in a child with an acquired immunodeficiency syndrome (AIDS)-like illness, prior to identification of the human immunodeficiency virus (HIV). Since that time further sporadic cases of this invasive infection have been reported in HIV and AIDS. We present two further cases and also a review of the current literature.

Malignant external otitis is classically associated with insulin-dependent diabetes mellitus probably due to generalized systemic immunodeficiency (Mowet and Baum, 1971). A unique case of malignant external otitis associated with Waldenstrom's macroglobulinaemia is presented.

A 69-year-old man presented with a three-month history of otalgia and tenderness of the right ear and a one-week history of a painful right parotid swelling. Examination revealed granulation tissue in the right ear canal with normal looking tympanic membranes and a parotid abscess. Repeated biopsies from the ear canal and parotid showed non-specific inflammation. Repeated cultures from both areas grew Ps. aeruginosa. The patient's condition improved following three weeks of intensive treatment for malignant otitis externa only to relapse five weeks after the end of treatment. He received a second course, only to improve temporarily. He developed a right facial nerve palsy five weeks after he was first seen, followed four months later by palsies of all cranial nerves except the olfactory, before dying, seven months after his first appointment.

The radiological, histological and post-mortem findings are discussed.

Malignant external otitis is a progressive pseudomonal infection of the external auditory canal and adjacent structures. In the literature there is no unified policy regarding the management of malignant external otitis. The development of an effective nuclear scanning method and antibiotics active against Pseudomonas aeruginosa have helped in formulating our management policy. A review of four years personal experience with this condition is presented. All of our cases were cured from the disease with no fatality. Gallium67 citrate scans showed that antipseudomonal treatment should continue for up to three months.