malignant external otitis

 A 72-year-old patient withlong-standing Type 2 diabetes mellitus presents with complaints of pain in his right ear with purulent drainage. On physical exam, the patient is afebrile. The pinna of the left ear is tender, and the external auditory canal is swollen and edematous. The peripheral white blood cell count is normal. The organism most likely to grow from the purulent drainage is :

• a. Pseudomonas aeruginosa
• b. Staphylococcus aureus
• c. Candida albicans
• d. Haemophilus influenzae
• e. Moraxella catarrhalis

 The answer is a.

Ear pain and drainage in an elderly diabetic patient must raise concern about malignant external otitis. Presence of swelling and inflammation of the external auditory meatus strongly suggests this diagnosis. This infection usually occurs in older diabetics and is almost always caused by organism Pseudomonas aeruginosa.

Haemophilus influenzae and Moraxella catarrhalis frequently cause otitis media but not external otitis.

Acute otitis externa with the canal somewhat narrowed from edema and obstructed by desquamating epithelium, soft cerumen, and purulent discharge; this must be removed to visualize the tympanic membrane and to allow ototopical therapy to penetrate to all the superficially infected areas of the canal skin.