Polite Dissent

A college-age patient came in complaining of large white spots on both of his arms. He told me that there had been white spots like these on his arms for years. They had actually been worse when he was younger, but he was going on a trip to Mexico so wanted to get them cleared up before Spring Break. The spots were present year round and did not get worse during any particular season. They itched, and he had tried various over the counter treatment without success.

On exam, the patient had several irregularly-shaped hypopigmented macules* on the upper and lower arms. The lesions were 1-2 centimeters in diameter and had a fairly diffuse border. They were not inflamed and there was no flaking or scaling.

The most common cause of light-colored spots in my clinic is tinea versicolor (TV). TV is caused by an overgrowth of a fungus that commonly grows on the skin. It worsens in warm conditions, and is most common in tropical climates and during the summer months. By my experience, the lesions are usually found on the shoulders and upper trunk. Sometimes they itch, but they usually do not. The spots have a well defined border and are often slightly flaky. Under a Wood Lamp (black light) the lesions will fluoresce, and skin scrapings treated with potassium hydroxide (KOH) have a definitive spaghetti-and-meatballs appearance under the microscope. Topical medications are the best treatment for TV.

This patient, however, did not have TV. His lesions did not have well-defined borders, but instead blended in with the normal skin so that it was hard to tell the exact spot where the lesion started. They also appeared much lower on the arms than versicolor usually does. They did not light up under a Wood lamp and the KOH examination was negative.

This patient has a condition known as pityriasis alba. The cause is unclear, though some dermatologists believe it may be a related to eczema. Itching, although uncommon, has been known to occur. Pityriasis alba occurs most commonly in children and goes away on its own as the patient gets older. It is extremely rare after age 25. Time is the best treatment, though there have been some successes with mild topical steroids and light therapy.

The patient was happy that I was able to diagnose his condition, but disheartened by the fact that there are no good medical treatments. We decided to try some 1% hydrocortisone cream and hopefully he’ll have good results before he heads south for Spring Break.

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*Psst! Here’s a secret for all you non-medically inclined readers. Hypopigmented means that a rash has less pigment than normal skin and is lighter in color. Macule refers to a flat lesion (like a freckle). Don’t let the other doctor know I told you…