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Joe R. Monroe, PA-C, MPAS, DEPARTMENT EDITOR
The patient who feared she had “Michael Jackson’s disease”
Joe R. Monroe, PA-C, MPAS
The author practices at The Dermatology Clinic, Oklahoma City, Okla, and is the founder and President of the Society of Dermatology Physician Assistants. He has indicated no relationships to disclose relating to the content of this article.
A 54-year-old woman was referred to the dermatology clinic for evaluation of asymptomatic lesions on her arms and legs. The lesions had been present for several years and were growing slowly in number and intensity. The patient was in excellent health otherwise. Her concern about the lesions stemmed from her family’s comments about her “Michael Jackson’s disease,” which she was convinced would spread over her whole body.
Examination showed a dense collection of hypopigmented macules on the extensor surfaces of her arms and to a lesser degree on her legs (see Figure 1). No scale was seen, but a faintly atrophic epidermal surface was noted on most of the lesions, which were decidedly annular in shape. The patient’s wrists, fingers, knees, elbows, and face were free of any such lesions.
Given the facts as presented, the most likely diagnosis is
• Idiopathic guttate hypomelanosis
• Vitiligo
• Seborrheic keratoses
• Pityriasis alba
Discussion
The correct answer is idiopathic guttate hypomelanosis (IGH), which is an extremely common disorder affecting 50% of persons older than 40 years and approximately 70% of those older than 60. IGH differs from vitiligo in a number of ways, including the distribution of the lesions and the patient population involved, but the main distinguishing feature of IGH is that the pigment loss is only partial. In vitiligo, the pigment loss is complete. Vitiligo also is far from rare, but it is nowhere near as common as IGH and, in its most common forms, predominates on high-friction areas such as the perioral area, knuckles, wrists, elbows, and knees.
Seborrheic keratoses are, by definition, epidermal lesions composed of “stuck-on” scale that is obvious on close examination. This contrasts sharply with the smooth, even, atrophic surface of IGH lesions. Seborrheic keratoses can appear hypopigmented on darker skin, even though far more typically they are brown or even black in color.
Pityriasis alba is the name given to the hypopigmented, papulosquamous annular lesions often found on the face and arms of darker-skinned patients—mostly children—who lose pigment as a postinflammatory consequence of eczema. The pigment loss is partial and gradual as the margins of these annular lesions are approached, which differs markedly from the relatively sharp margins and invariably smooth surfaces of the lesions of IGH.
Diagnosis and treatment IGH is almost exclusively seen on sun-exposed portions of the arms and legs, so sun almost certainly plays a part in its genesis; however, the almost complete lack of involvement of the face suggests that other factors are involved. Biopsy is occasionally necessary to differentiate IGH from vitiligo or other less common conditions in the differential diagnosis, such as sarcoidosis, mycosis fungoides, or tuberous sclerosis. Aside from sun protection, a light application of liquid nitrogen has helped some patients with IGH.
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