Descriptions of the dermoscopic features of acral hypokeratosis (AH) are few. Clinically it can resemble other entities, such as Bowen disease or porokeratosis of Mibelli. Although AH is considered a benign pathology, in 2010 a case with actinic keratosis in the hypokeratosic epidermis and underlying elastosis was reported [ 1 ] , hence the importance of knowing the dermoscopic findings for an early diagnosis and to rule out other differential or coexisting diagnoses.
Our case series was comprised of 4 patients with AH confirmed by biopsy in the hypothenar eminence. Figure 1A shows AH in a 61-year-old and Figure 1B a 78-year-old woman with a 10-year history of AH. Dermoscopy revealed pink areas on a red milky blush with scattered red dots, step-like scales at the periphery, and elongated whitish structures in a fibrillar raindrop pattern ( Figure 1, C and D ).
Figure 1 .
Clinical and dermoscopic features. (A and B) Cases 1 and 2: Atrophic erythematous plaque with an irregular hyperkeratotic border. (C) Dermoscopy shows pink areas on a red milky blush with scattered red dots, step-like scales at the periphery and elongated whitish structures in a raindrop pattern. (D) Dermoscopy shows red milky blush, pink islets with dotted vessels, elongated whitish structures in raindrop pattern and staircase sign. (E) Case 3: Depressed erythematous plaque, surrounded by an hyperkeratotic border. (F) Dermoscopy showed a red dot pattern over a homogeneous red-yellow area.
The third case corresponded to asymptomatic AH ( Figure 1E ) that had developed 2 weeks after a cutting wound in a 30-year-old woman. Dermoscopy showed a red dot pattern over a homogeneous red-yellow area ( Figure 1F ). The fourth case was a 54-year-old woman affected by AH for 8 years ( Figure 1G ). Dermoscopy revealed a fine white pseudonetwork, pink stiff areas on a red milky blush with red dots, step-like scales at the periphery, and elongated whitish structures in a fibrillar raindrop pattern. ( Figure 1H ). Microscopy revealed an area of hypokeratosis demarcated by a sharp and frayed cut-off from uninvolved acral skin with discrete hypogranulosis, dilated blood vessels in the papillary dermis, and slightly thickened collagen fibers in the reticular dermis ( Figure 2 ).
Figure 2 .
Histology displays an area of hypokeratosis demarcated by a sharp and frayed cut-off from uninvolved acral skin with discrete hypogranulosis, dilated blood vessels in the papillary dermis and slightly thickened collagen fibers in the reticular dermis (H&E, ×10).
Previous case series reported star-like desquamation at the periphery, and a well-demarcated erythema with reddish dots. These structures correlate with histopathological studies showing a sharply demarcated area of hypokeratosis, dilated capillaries in the papillary dermis and vessels in the upper reticular dermis [ 2 ] . A recent case report of congenital plantar AH showed a white thin scale and a reticulated surface with no visible acrosyringia opposing the typical dermoscopic acral pattern [ 3 ] .
Our study revealed different dermoscopic findings than previously published: A fine white pseudonetwork and elongated whitish structures in a “raindrop pattern” found in those patients with longstanding AH and could be correlated with the increasing collagen proliferation and thickening. Thus in our case of 2-weeks’ onset AH, only a yellowish-red blush and red dots with peripheral step-like scales were distinguishing.
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