Focal acral hyperkeratosis
Onset is gradual and typically occurs during childhood and adolescence, with the vast majority of cases developing before the age of 20 years. FAH usually progresses with advancing age (increased number and size of hyperkeratotic papules). Although asymptomatic, patients often present with concerns about cosmetic appearance. Multiple treatment modalities have been attempted without much success.
Clinically, FAH is identical to acrokeratoelastoidosis (AKE). The major difference between these two disorders is the histopathologic finding of elastorrhexis (fragmentation and degeneration of elastic fibers) in the dermis, a feature that is present in AKE but absent in FAH. In addition, hyperhidrosis is rarely associated with AKE but not FAH. It is still controversial whether FAH is a distinct entity or a variant of AKE.
Related topic: Punctate palmoplantar keratoderma
L85.8 – Other specified epidermal thickening
400115004 – Focal acral hyperkeratosis
Differential Diagnosis & Pitfalls
- Acrokeratoelastoidosis (AKE) – Identical clinical appearance as FAH with distinguishing histopathologic finding of elastorrhexis in the dermis, which is not present in FAH.
- Verruca plana (flat warts) – More flat-topped and pink or red-brown, less hyperkeratotic, usually occurs on dorsal aspects of hands / feet, and frequently affects other sites of the body as well (especially face and lower legs); histopathologic examination will reveal characteristic koilocytes and perinuclear vacuolization of keratinocytes.
- Epidermodysplasia verruciformis – Two types of lesions that can resemble flat warts or tinea versicolor, confluence is a more prominent feature, other sites of the body are frequently involved, other types of warts may be present, and histopathologic examination will reveal characteristic perinuclear vacuolization of keratinocytes in granular and upper spinous layers.
- Acrokeratosis verruciformis of Hopf – Usually present at birth or manifests in early childhood, more flat-topped and pink or red-brown, usually occurs on dorsal aspects of hands / feet and may occur on other areas of body as well (including elbows, knees, forearms, and lower legs), histopathologic examination will reveal papillomatosis and frequent "church spire" configuration.
- Punctate porokeratosis – Papules have thin, raised margin that corresponds to the characteristic "cornoid lamella" on histopathologic examination.
- Punctate palmoplantar keratoderma – Papules are smaller and irregularly distributed over the entire palmoplantar surface, and histopathologic examination will reveal compact columns of massive hyperkeratosis over a sharply limited area of epidermis with a more prominent depressed epidermis below the hyperkeratosis.
- Lichen planus – Usually violaceous in color with overlying Wickham striae, frequently affects other sites of body as well (eg, flexural surfaces, mucosal surfaces, genitals), and histopathologic examination will reveal characteristic lichenoid-interface lymphocytic reaction.
- Darier disease – Keratotic red-to-brown papules and keratin-filled depressions can be found over the entire surface of the palms / soles, other characteristic skin and nail findings will be present, and acrokeratosis verruciformis of Hopf-like lesions on the dorsal aspects of hands / feet can also occur; histopathologic examination will reveal acantholytic dyskeratosis.