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Monday, February 14, 2011

Use Clinical Insight, Biopsies to Diagnose Causes of Hypopigmentation

By: DAMIAN MCNAMARA, Internal Medicine News Digital Network

NEW ORLEANS – When a patient presents with patches of lighter skin and you immediately go through the most likely clinical culprits in your head, don’t forget to include hypochromia in your differential diagnosis among the common hypopigmentation disorders, Dr. James J. Nordlund said.

Although most diagnoses will not be definitive without a biopsy, your clinical suspicions are essential to alert your pathologist to look for subtle signs that in some cases can make a big difference in clinical treatment and outcomes, Dr. Nordlund said.

Mycosis fungoides, progressive macular hypomelanosis, sarcoidosis, and pityriasis alba are true hypopigmentation disorders characterized by decreases in melanin in the skin. In contrast, hypochromia or patches of light- or white-colored skin, can throw you off until the pathology report reveals normal melanin levels.

"These are some of the problems I struggle with. They are common and I see them every day, and I certainly have some successes and failures," Dr. Nordlund said at the annual meeting of the American Society of Dermatology.

A misdiagnosis of hypopigmentation "is probably the biggest problem when we don’t get a great response in patients. You have to ask yourself if the condition is related to a melanin decrease," said Dr. Nordlund, professor of clinical dermatology at Wright State University in Dayton, Ohio.

Nevus anemicus is an example of hypochromia. This vascular anomaly often mimics hypopigmentation, Dr. Nordlund said. Scars also can cause hypochromia. A Wood’s lamp might reveal excessive collagen in the dermis and decreased vascularity with scar tissue. "It appears to be depigmentation but it’s not."

Mycosis fungoides, in contrast, is a true hypopigmentation disorder. The ultraviolet glow of a Wood’s lamp, however, will be insufficient for most diagnoses. The clinical presentation is vague, so a biopsy helps to identify this condition, Dr. Nordlund said. He performs longitudinal shave biopsies if there is any doubt.

"It’s important to keep hypopigmentation mycosis fungoides in mind as a cause of hypopigmentation on the trunk and extremities," Dr. Nordlund said. "Alert your pathologist to this possible diagnosis so they can look for the subtle signs."

Mycosis fungoides is more common in darker skin, affects both children and adults, and generally has a good prognosis. Treatment response generally is better with narrow-band ultraviolet B phototherapy or psoralen and ultraviolet A (PUVA) therapy than with topical steroids.

You also may see hypopigmentation in association with sarcoidosis, a granulomatous inflammation that most often presents as red, indurated nodules on the skin, although it can affect any or all organs. A punch biopsy can confirm if a lesion is sarcoid, Dr. Nordlund said. "You really cannot be sure except with histology."

A biopsy also helps to distinguish mycosis fungoides or sarcoidosis from a third hypopigmentation disorder called progressive macular hypomelanosis. Ill-defined macules typically begin on the back and spread, sparing the face, in darker-skinned patients. A meeting attendee asked if there are diagnostic studies for this condition. Dr. Nordlund said no. "I biopsy them, because I don’t think it’s distinguishable from mycosis fungoides or sarcoidosis. That is all I do, biopsy." Pathology generally reveals a mild-to-moderate deficiency of melanin.

This is "one disorder I see too often for my own desires. It’s hard to treat," Dr. Nordlund said. PUVA is an option, but the hypopigmentation can return after treatment is discontinued. Some researchers suggest the condition is a form of Pityrosporum (now called Malassezia) infection, he added. "Minocycline 100 mg with benzoyl peroxide – I’ve tried this off-label approach – and sometimes I get a response."

There also is an idiopathic form. In idiopathic guttate hypomelanosis, melanocytes usually are present but melanization is suppressed. The epidermis will appear normal to slightly atrophic. Pathogenesis might be genetic and/or due to exposure to sunlight, "but I can’t convince myself of the sunlight etiology," Dr. Nordlund said.

Also consider pityriasis alba, characterized by hypopigmentation with slight scaling but no pruritus, in your differential diagnosis. This condition is very common in children and young adults.

"From my own experience, UV light is not very helpful," Dr. Nordlund said. "Oftentimes the mistake is to use high-potency steroids, which also suppress melanin. You essentially turn off melanin production and don’t get a good response." Instead, he recommended long-term, mild steroid treatment with a product such as Desonide Lotion (available as a generic).

Tinea versicolor is a common infection that also causes hypopigmentation. The yeastlike Malassezia furfur fungus infects the stratum corneum. The condition is easily treated with topical or oral ketoconazole, Dr. Nordlund said, but complete response can take time. "Warn patients that hypopigmentation can persist for months."

Dr. Nordlund said that he had no relevant financial disclosures.