Background

In 1968, Bart et al^[1] described 10 cases of an uncommon acquired growth that was located on the fingers. Although it clinically resembled a cutaneous horn or rudimentary supernumerary digit, it had distinct histopathological findings. The authors named this growth acquired digital fibrokeratoma (ADFK). Subsequently, Pinkus^[2] reported 28 more cases; however, these lesions occurred not only on the fingers, but also on the proximal hand, toes,^[3] sole, and one in the prepatellar region. For this reason, Verallo et al suggested the entity might more appropriately be called an acral fibrokeratoma.^[4]

Similar growths have been reported to occur in the subungual or periungual region of patients with tuberous sclerosis, and they are referred to as Koenen tumors or garlic clove fibromas. They differ, however, in that they tend to be multilobulated and involve several digits and, histologically, may have atypical stellate myofibroblasts.^[5]

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Pathophysiology

Despite the fact that most patients deny a history of precedent trauma, the major hypothesis is that subclinical injury contributes to the development of acquired digital fibrokeratomas.^[1] One case report describes an ADFK on the toe developing simultaneously with gingival overgrowth in a renal transplantation patient on cyclosporine, which the authors suggested may represent a causal association.^[6]

Epidemiology

Frequency

Currently, no means of tracking nonmelanoma skin cancer, much less various benign dermatological conditions, are available in the United States; therefore, the actual incidence of acquired acral fibrokeratoma is unknown. Most cases of acquired digital fibrokeratoma reported in the literature involve individual case reports presented because of the lesions' unusual size, location, histological features, or association with other conditions. Only a few reports of describe a series of patients, with 50 patients being the most reported from any one institution.^[7] Therefore, whether acquired digital fibrokeratoma is rare or rarely reported remains unclear.

Race

Acquired digital fibrokeratomas have been reported in persons of all races.

Sex

Acquired digital fibrokeratomas seem to have a slight male predominance; however, at this time too few cases have been described to adequately assess the significance of any sexual predilection.^[8]

Age

The patients reported with acquired digital fibrokeratomas range in age from 12-70 years, with most cases occurring in middle-aged adults. Clinically similar lesions that occur in young children are more likely to represent rudimentary supernumerary digits.

Prognosis

Acquired digital fibrokeratomas are benign stationary lesions that are more cosmetically bothersome than they are problematic. However, patients who have been reported to have giant acral digital fibromas on the dorsum or plantar surface^{[9, 10, 11]} of the foot may report some discomfort.^[10]

Clinical Presentation