A 40-year-old Vietnamese man presented for an asymptomatic rash on his back and chest that had been present for the past decade

[Medicoman]

What’s the diagnosis? A 40-year-old Vietnamese man presented for an asymptomatic rash on his back and chest that had been present for the past decade. Over the years, he was treated by multiple providers, including 7 dermatologists. The rash had not improved despite treatment with topical corticosteroids, calcineurin inhibitors, various bland emollients, ketoconazole cream and shampoo, oral fluconazole, and various over-the-counter antifungal medications. On examination, the patient had nonscaly, hypopigmented macules coalescing into patches on his chest and back (Fig 1). He denied itching, pain, or other symptoms. Potassium hydroxide test result was negative and biopsy revealed no pathologic changes. Wood’s lamp examination revealed perifollicular, punctiform, red-orange fluorescence (Fig 2).

• A. Pityriasis alba
• B. Pityriasis (tinea) versicolor
• C. Postinflammatory hypopigmentation
• D. Progressive macular hypomelanosis
• E. Vitiligo

exp:

Answers:

• A.Pityriasis alba—Incorrect. Pityriasis alba is a skin condition of hypopigmentation that is associated with atopic dermatitis. It predominantly affects children, and lesions typically involve the face. Wood’s lamp examination does not accentuate the hypopigmentation or exhibit perifollicular fluorescence.
• B.Pityriasis (tinea) versicolor—Incorrect. Like PMH, tinea versicolor is characterized by macular areas of hypopigmentation that typically involve the chest and upper portion of the back. However, tinea versicolor would be expected to improve with antifungal medications and does not exhibit red-orange perifollicular fluorescence under Wood’s lamp examination. Instead, black-light illumination of skin affected by tinea versicolor reveals a yellow-orange fluorescence of the yeast. Additionally, potassium hydroxide examination characteristically reveals hyphae and yeast in a “spaghetti and meatballs” pattern.
• C.Postinflammatory hypopigmentation—Incorrect. Postinflammatory hypopigmentation describes the loss of pigment in the skin after the resolution of an inflammatory process. The pathogenesis is thought to be due to the loss of functional melanocytes but is not completely understood. Wood’s lamp examination does not accentuate hypopigmentation or reveal perifollicular fluorescence.
• D.PMH—Correct. PMH is a skin condition of hypopigmentation that was undescribed in the scientific literature until 1988.[1](javascript:void(0) It is clinically characterized by macular areas of hypopigmentation, typically on the chest or back, which exhibit perifollicular red-orange fluorescence under Wood’s lamp examination. This characteristic finding with such an examination was first described by Wu et al in 2010.[2](javascript:void(0) In their study of 21 patients with a previous diagnosis of PMH and with a previous negative potassium hydroxide test result, all 21 had perifollicular fluorescence with the application of black light. This finding has not been shown to be associated with any other hypomelanotic conditions and may therefore be considered pathognomonic for PMH. Currently, there are reports of cases studied with dermatoscopy; however, in hospitals in which there is no such tool or experience is limited, the use of Wood’s lamp is an excellent method of differentiating PMH from other conditions of hypopigmentation, thus avoiding misdiagnoses and unnecessary treatments. This report supports the utility of Wood’s lamp as a diagnostic tool for hypopigmented lesions.
• E.Vitiligo—Incorrect. Vitiligo is an acquired disorder characterized by macules and patches of depigmentation that result from a progressive loss of functional melanocytes. Although clinical presentation may be similar to that of PMH, Wood’s lamp examination of areas affected by vitiligo does not reveal red-orange perifollicular fluorescence and demonstrates complete depigmentation rather than the hypopigmentation of PMH.