Case Report
An 11-year-old boy presented with atraumatic thickening of the skin on the bilateral distal and proximal interphalangeal joints of 1 year’s duration. The patient also noted small bumps of unknown duration across the bilateral palms and soles with prominence on the lateral aspects. The patient previously used over-the-counter topical wart removal treatment and topical salicylic acid with minimal improvement. The patient reported no pertinent medical or surgical history, although there was a family history of Alport syndrome, predominantly in male relatives. The patient’s father and paternal grandfather were noted to have similar lesions on the palms.
On physical examination, multiple pink to flesh-colored hyperkeratotic plaques were noted over the proximal and distal interphalangeal joints of the bilateral hands (Figure 1A). Upon close inspection, there were small flesh-colored and slightly translucent papules in a linear distribution on the palmar surfaces of the hands (Figure 2A) with predominance on the thenar and hypothenar eminences. The flexural creases of the bilateral wrists also revealed linear flesh-colored papules. The same small flesh-colored and translucent papules also were noted on the plantar surfaces of the bilateral feet (Figure 2B).
Figure 1. Hypertrophic knuckle pads over the proximal and distal interphalangeal joints on the right hand before (A) and after daily treatment with urea cream 10% for 1 month (B).
Figure 2. Small flesh-colored, slightly translucent papules were linearly distributed on the palmar surface of the right hand (A) and the plantar surface of the right foot (B).
A biopsy was obtained from one of the small translucent papules on the left palm. Hematoxylin and eosin–stained sections revealed elevated compact orthokeratosis with an underlying central epidermal dell (Figure 3). A diagnosis of marginal papular keratoderma was made and further elastin staining was completed. Elastin stains showed marked thinning of the elastin fibers throughout the reticular dermis. Many elastin fibers in the reticular dermis demonstrated a fine arborizing pattern that normally is only evident in the papillary dermis (Figure 4). Acrokeratoelastoidosis (AKE) was diagnosed histopathologically, and knuckle pads were diagnosed clinically.
Figure 3. Histopathology revealed elevated compact orthokeratosis with an underlying central epidermal dell (H&E, original magnification ×4).
Figure 4. Elastin stain showed arborizing thin elastin fibers throughout the reticular dermis (original magnification ×40).
Because the patient was asymptomatic, he did not want treatment of AKE. He had marked improvement of the knuckle pads after 1 month with daily application of urea cream 10% (Figure 1B), and intermittent use was required for maintenance.