Yellowish Papules on the Palms: a Diagnostic Challenge.

A 72-year-old woman was referred to the outpatient service of our Dermatology Unit in Milan for a 40-year history of an asymptomatic palmar dermatosis. Upon physical examination, separate, minute, translucent, yellowish papules were seen on the patient's palms and wrists (Figure 1). Plantar surfaces were spared. Likewise, no involvement of the nail apparatus could be appreciated. No family history was reported for such condition. Histopathological examination showed focal orthokeratotic hyperkeratosis with an underlying epithelial dell. The dermis lacked pathological changes, and no inflammatory infiltrates could be observed. Components of the extracellular matrix were normally represented (Figure 2). Focal acral hyperkeratosis. First described by Dowd et al. in 1983,1 focal acral hyperkeratosis (FAH) is presently classified within the group of palmoplantar keratodermas. From a nosological perspective, FAH appears to be closely related to acrokeratoelastoidosis (AKE) of Costa (also known as punctate palmoplantar keratoderma type 3),2 and it is still debated as to whether FAH represents a distinct condition or simply a variant of AKE. Both can be inherited or more rarely sporadic, with onset generally occurring during the second or third decade of life.3 From a practical point of view, the clinical picture is superimposable, with both entities showing multiple yellowish to flesh-colored, waxy, polygonal or round, smooth, sometimes umbilicated, hyperkeratotic papules, symmetrically distributed over the palms and soles, typically along—but not limited to—the lines of transgredience. The lesions may become confluent over time. Onychodystrophy has been described as a distinctive yet possibly underreported feature of FAH.4 Knuckle pads have also been observed.5 On histology, lack of elastorrhexis provides reliable differentiation of FAH from AKE. Also electron microscopy reveals normal elastic fibers and fibroblasts in FAH, in contrast to AKE. Increased expression of proliferation (Ki-67, proliferating cell nuclear antigen [PCNA]) and differentiation (involucrin) markers have been documented in FAH, leading to a possible reclassification as a keratinization disorder.3 Warts, degenerative collagenous plaques of the hands/keratoelastoidosis marginalis of the hands, acrokeratosis verruciformis of Hopf, and punctate palmoplantar keratoderma type 1 and type 2 need to be considered in the differential diagnosis (Table 1).5 Since FAH is an asymptomatic and relatively benign condition, treatment options should be discussed in accordance with patients' aesthetic and/or functional preferences. Therapy generally aims to reduce hyperkeratosis with topical (e.g., urea, salicylic acid, topical retinoids) or systemic (e.g., acitretin) agents.3 In conclusion, our case presented a diffuse involvement of palmar surfaces and lacked accompanying features such as nail changes, knuckle pads, or extensor surface spreading. Which of the following histological patterns better differentiate FAH from AKE? Which of the following markers has been documented in FAH? All authors have made substantial contribution to the work and have approved the final version of this article. Open Access Funding provided by Universita degli Studi di Milano within the CRUI-CARE Agreement. Written informed consent was obtained from the patient for publication of this report and accompanying images.