Quiz

Spiny keratoderma of the palms and soles (SKPS) is a rare skin disease that was first described by Brown (1) in 1971 as “punctate keratoderma”. Since then, several terms have been used to describe this dermatosis, such as punctate porokeratotic keratoderma, hyperkeratose palmo-plantaire filiforme and porokeratosis punctata palmaris et plantaris. Osman et al. first coined the designation “spiny keratoderma of the palms and soles” (6). More recently, this term has gained favour because it describes more accurately the clinical and pathological findings.

The aetiology of SKPS remains unclear. Two variants of SKPS can be distinguished; a hereditary and an acquired variant. The hereditary variant is inherited by an autosomal dominant trait and manifests typically between the ages of 12 and 50 years. No other systemic diseases or malignant conditions have been associated with SKPS (2).

The acquired form, which is the diagnosis in our patient, appears mostly after the age of 50 years. Associations with internal and cutaneous malignancy or systemic diseases have been reported in some acquired cases (2). For example, SKPS has been found associated with malignant melanoma (3), rectal carcinoma (4), breast cancer (5), type IV hyper-lipoproteinaemia (6) and autosomal dominant polycystic kidney disease with liver cysts (7). In addition, there is an accumulation of SKPS cases observed in patients with a history of manual labour or medication with HMG-CoA reductase inhibitors (6). To our knowledge, the present case is the first report of SKPS associated with an atypical fibroxanthoma. Age-appropriate cancer screenings and regular physical examinations are recommended for early detection of any associated internal or cutaneous disease in patients with the acquired form of SKPS.

The clinical picture of SKPS is pathognomonic. Typically there are multiple, symmetrical, firm, keratotic papules 1–2 mm in height. The lesions can either be limited to the palms or affect the palms and soles. The majority of reported cases have had palmar involvement only. The disease is also called “music box spine dermatosis” due to the clinical appearance of the papules (8).

SKPS is probably under-reported and under-diagnosed because such patients do not seek medical advice since most cases cause minimal discomfort or are asymptomatic. In addition, unfamiliarity with the disease due to its rarity may prevent the proper diagnosis. In some cases clinical symptoms, such as pain, pruritus, a tingling sensation or rough feeling, are observed (6).

Diagnosis of SKPS can be confirmed by histopathology, showing a compact vertical column of parakeratosis above a fine granular layer. In contrast to the cornoid lamellae of porokeratosis, in SKPS dyskeratoses are usually absent below the granular layer. Examination using a Wood’s lamp shows white fluorescence that looks similar to stars under the moonlight (9).

Treatment of SPKS is difficult and not well established. Management involves treatment with 0.05% tretinoin (7), ammonium lactate 12% lotion (7), salicylic acid (6), 0.002% tacalcitol ointment (10) and topical 5-fluorouracil (6). Long-term therapy is needed to prevent relapse with all forms of treatment. Successful therapy has also been reported with the use of acitretin 25–30 mg daily (11). One case report even states that the patient remained clear of skin lesions for at least 18 months after cessation of acitretin (12). Other therapeutic approaches include mechanical debridement, such as dermabrasion or excision of a small number of lesions (6, 8). No spontaneous remissions have been reported.