Porokeratosis (Mibelli). Presented by Dr. Harold Price.
This 10-year-old boy developed a few asymptomatic lesions on the left arm and the neck during the past year. The lesions appear to be slowly enlarging.
The previous history is noncontributory.
On the extensor surface of the left arm there is a nickle-sized plaque, consisting of a depressed flat center surrounded by an arciform elevated erythematous border which has a hyperkeratotic summit. When the hyperkeratotic material is removed, there can be seen a fine slender furrow running along the surface of the dike-like border. On either side of the neck are a few early small lesions, consisting of hyperkeratotic dome-like papules which already show some central involution. One lesion on the left forearm has a linear configuration.
Microscopic examination reveals considerable lamellar hyperkeratosis and acanthosis, with follicular dilatation and hyperkeratotic plugging. In a few areas there are deep indentations of