CASE #1: Punctate keratoderma of the palm and sole

Palmoplantar keratodermas (PPKs) are divided into three types. Type I (the form most likely to be affecting our patient) is punctate keratoderma, which manifests with numerous hard wartlike dells on the palms or soles. The lesions range from 0.1 to 2 mm in diameter and depth. Onset is between the ages of 12 and 20 years; incidence is 1-1.7/100,000 persons. Type II PPK, or filiform keratoderma, features spicules that resemble music box spines on the palms and soles, although the disorder can also occur elsewhere on the body. Onset usually occurs between the ages of 12 and 50 years. Type III PPK, or marginal keratoderma, manifests with oval or polygonal keratotic dells on the borders of the hands, feet, and wrists as well as in the center of the palms and soles. The disorder usually appears in late childhood or early adulthood. Type III PPK can be associated with diffuse palmoplantar keratoderma, hypohidrosis, and nail abnormalities. Focal hyperkeratosis can be seen at the pressure points, due to mechanical rubbing, or in areas of the skin that are irritated.

Type I PPK can be acquired or hereditary. Acquired punctate keratoderma has a variety of causes ranging from essential (idiopathic/noninherited) to neoplastic. Punctate PPK of the palmar creases (PPPK[PC]) occurs in black patients and is likely the most common type of essential PPPK. (The disorder may have a genetic basis, but that has not been defined.) Other names for PPPK(PC) include keratotic pits of the palmar creases, punctate keratosis of the palmar creases, hyperkeratosis punctata of the palmar creases, keratosis punctata, keratoderma punctata, hyperkeratosis penetrans, and lenticular atrophia of the palmar crease. PPPK(PC) has been said by some to have associations with atopy, knuckle pads, dermatitis herpetiformis, striate keratoderma, psoriasis, Dupuytren contractures, pterygium inversum unguis, and focal acral hyperkeratosis.

Acquired punctate keratodermas caused by arsenic are termed arsenical keratoses. Arsenical keratoses look like multiple hypertrophic actinic keratoses on the palms and soles (an uncommon location for actinic keratoses). Arsenic is a systemic carcinogen, and arsenical keratoses can manifest contemporaneously with angiosarcoma of the liver, squamous cell cancer of the skin, and bronchial adenocarcinoma. Old age and internal malignancies can correlate with idiopathic palmoplantar keratoderma. Breast, renal, colon, and lung cancer can be associated with idiopathic porokeratotic palmoplantar keratoderma, a condition that has been liked to secondary syphilis.

Inherited punctate keratodermas are one of the three types of inherited palmoplantar keratoderma that include focal, diffuse, and punctate varieties. There are three categories of hereditary punctate PPKs: type I includes Buschke-Fischer-Brauer disease, keratosis punctata, and keratosis papulosa; type II is porokeratosis punctata palmaris et plantaris, and type III comprises acrokeratoelastoidosis lichenoides. Punctate PPK affects men and women equally in an autosomal dominant pattern with variable penetrance. No specific genes have been linked to inherited PPKs, although some linkages (e.g., 18q24.13-8q24.21 and 15q22-15q24) for types I have been suggested.

Wood’s light can excite white fluorescence of type I hereditary PPK. Compared with normal controls, kindred with type I PPK seem to suffer more malignancies (adenocarcinomas of the kidney, breast, pancreas, and colon and Hodgkin disease). Histopathologic examination can demonstrate hyperkeratotic epidermis without columns of parakeratosis or elastorrhexis. On electron microscopy, the basal cells of the epidermis may contain enlarged nucleoli and abundant tonofilaments, with keratohyalinlike granules confined to the upper part of the stratum spinosum.

First-line treatment of all types of PPK usually involves moisturizers that contain natural moisturizing agents, such as lactic acid (12%) and urea (compositions that are 40% or higher). Salicyclic acid 3% and 6% can be helpful as well. Also beneficial are topical retinoids (adapalene [Differin], tretinoin, and tazarotene); in severe cases, acitretin can be used. Some dermatologists suggest that only mechanical debridement and excision are effective for PPK.