Spiny keratoderma is a rare, easily distinguishable variant of punctate keratoderma. It is characterized by a spiny texture with multiple hard keratotic outgrowths on the palms and soles. These spines are likened to an old-fashioned music box but have been labeled by other synonyms, such as palmar keratoses, punctate keratoderma, filiform hyperkeratosis, and punctuate porokeratotic keratoderma.
Although the cause is generally unknown, hereditary and acquired cases have been reported. The hereditary form is autosomal dominant and presents typically between the ages of 12 and 50 years. Acquired spiny keratoderma is associated with systemic disease and malignancy and usually appears after the age of 50 years.
Treatment of spiny keratoderma can be difficult, and the prognosis is uncertain. Obtaining a thorough personal and family history, routine medical exam, and age-related screenings for cancer is necessary. Although management is not well established, some positive results have been procured with a variety of topical therapies and acitretin.
History of present illness
A 60-year-old White man presented to the dermatology clinic as an established patient who was last seen only 2 weeks prior for a body check. His chief complaint was ‘a slight rash’ on his abdomen. He did not complain of the subtle hyperkeratotic papules on the palmar surfaces of his hands that had been there for 2 years until questioned by the practitioner. The patient then admitted that his clothes, particularly his gloves, would cling to his hands. He denied any associated symptoms such as pruritus, pain, or burning.
The patient had a dermatologic history of squamous cell carcinoma in situ, dysplastic nevi, and actinic keratoses. A former police officer of 30 years, he was a smoker for 40 years before quitting in 2011. He denied a history of drinking alcohol. He experienced hypertension, asthma, arthritis, benign prostatic hyperplasia, and prediabetes. He admitted to drinking well water most of his life. Past visits to his primary care physician for general age-related screenings and his family history had not revealed any remarkable findings pertaining to his keratoderma.
The exam showed multiple hard, 0.5- to 1-mm keratotic spicules dispersed throughout his bilateral volar surfaces of his palms and fingers. Although his palmar surfaces displayed redness, lesions did not have erythema (see Hard, discreet projections of spiny keratoderma and Lesions confined to palmar surfaces without similar lesions anywhere including his soles). There were no similar lesions anywhere else on his body including his soles.
Histologic features of two 4-mm punch biopsies in formalin from the left anterior palm of the hand and the right anterior palm of the hand indicated that the lesions were compatible with keratoderma. There was hyperkeratosis consistent with volar skin. A focus of well-defined parakeratosis was present, which extended above the hyperkeratosis. Beneath this, there was acanthosis with mild papillomatosis, and the granular cell layer was preserved. There was mild, chronic inflammation in the dermis. (N. Whitling, L. Cooper, J. Chung, pers. comm.)
There is histologic overlap in spiny keratoderma and porokeratosis; however, there is a lack of necrotic keratinocytes underlying the column of parakeratosis in this case and absence of the characteristic coronoid lamellae of porokeratosis, suggesting keratoderma (see Histology of keratoderma). (N. Whitling, L. Cooper, J. Chung, pers. comm.)
Spiny keratoderma is characterized by a spiny texture with multiple hard, keratotic micropapules on the palms and soles and may be pruritic.1,2 Brown delineated the first case of these multiple projections on the palms and soles in 1971.3
Spiny keratoderma is known by other names, including palmar keratoses, punctate keratoderma, filiform hyperkeratosis, and punctuate porokeratotic keratoderma, histology, and other nomenclature (see Classification of spiny keratoderma).4
A 2008 literature review reported 28 cases of spiny keratoderma. Of these, 19% were of hereditary origin (see Clinical variants of punctate palmoplantar keratoderma). The hereditary form is autosomal dominant and presents typically between the ages of 12 and 50 years.
Some consider spiny keratoderma a common under-reported dermatosis; therefore, the incidence and prevalence have not been fully determined. Acquired spiny keratoderma has been reported to be found in conjunction with systemic disease and malignancy such as, but not limited to, rectal, bronchial, renal, and breast carcinomas as well as leukemia, squamous cell carcinoma of the skin, and melanoma. Whether the occurrence of spiny keratoderma with a malignancy is truly paraneoplastic or coincidental is speculative.5
A diagnosis of malignancy most commonly follows the detection of spiny keratoderma lesions, which may persist after cancer removal.4 It is thought that the duration of time before malignancy is seen may be as long as 30 years.3
Systemic diseases have been cited coinciding with spiny keratoderma such as Darier's disease, Type IV hyperlipopro-teinemia, chronic renal failure, dyslipidemia, pulmonary tuberculosis, asthma, and myelofibrosis.5,6 The patient stated that he was diagnosed with asthma as a child and had an exacerbation around 2010, which prompted him to quit smoking. His asthma exacerbation preceded the keratoderma by a few years. As mentioned, the patient's family history was noncontributory, and he denied any family or personal history of melanoma, Type IV hyperlipoproteinemia, Darier's disease, chronic renal failure, tuberculosis, ichthyosis, keratoderma, or dyslipidemia.
Physical exam, blood count, chemistry panel, amylase, rheumatoid factor, alpha-fetoprotein, carcinoembryonic antigen, CA-15-3, CA-19-9, prostate-specific antigen, antinuclear antibody, rapid plasma reagin, HIV, QuantiFERON-TB gold test, thyroid stimulating hormone, chest X-ray, and computed tomography (CT) scans of the chest, abdomen, and pelvis were done to rule out associated conditions and malignancy. CT scans revealed a fatty liver, an enlarged prostate gland, mild sigmoid diverticulosis without diverticulitis, and multivessel coronary artery disease. A connection between this patient's asthma and his keratoderma would be conjectural, and careful follow-up is prudent. The patient's internist was notified, and his case was discussed.
Differential diagnoses include arsenical keratoses, porokeratoses, and verrucae vulgaris. Verrucae can share similarities to spiny keratoses but possess tiny black or red dots within the lesion representing thrombosed capillaries. Arsenical keratoses are a result of chronic arsenic toxicity from contaminated well water or from occupational exposure. The patient admitted to drinking well water much of his life; however, the lesions clinically and histologically did not present as arsenical keratoses. These corn-like papules typically are larger than spiny keratoderma and may even present as diffuse thickening on the palms, soles, and sometimes ears.1 They range in presentation from small scales to brownish crusts with rolled borders. Histologically, the lesions do not support a diagnosis of porokeratosis.
Unfortunately, treatment for spiny keratoderma has not been consistently effective or established. Various topical therapies have been attempted, such as 5% fluorouracil cream, 12% ammonium lactate, retinoids, urea, corticosteroids, and salicylic acid. A report of an active form of Vitamin D3 (tacalcitol 0.002% ointment), showed improvement in skin lesions.7 Positive outcomes have been achieved with acitretin as well.5
The patient was prescribed topical 40% urea and halobetasol; both resulted in insignificant improvement. Acitretin was dosed at 25 mg twice daily, inevitably reducing lesion count and softening remaining lesions. After 6 weeks of significantly reduced lesion count, acitretin was tapered to 25 mg once daily. The patient experienced minimal adverse reactions, including a short span of dryness, and his lab work was unremarkable. Duration of treatment with acitretin varies with individual responses. He continued acitretin 25 mg daily for approximately 4 months with one unsuccessful 3-week holiday as his keratoderma recurred. Acitretin given every other day to every third day with continued lab monitoring has been successful. Only excision or debridement has effectually attained permanent results.1
Although spiny keratoderma is interesting, it can be frustrating for both the provider and the patient, especially as it relates to its origin and treatment. The heralding of this condition can be a flag for a developing malignant condition. Therefore, collaboration with the general physician overseeing age-appropriate screenings can assist in a timely diagnosis and treatment for such a patient.
1. James WD, Berger TG, Elston DM. Andrews' Diseases of the Skin
. 11th edition. Philadelphia, PA: Saunders; 2011.
2. Osman Y, Daly TJ, Don PC. Spiny keratoderma of the palms and soles. J Am Acad Dermatol
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3. Saha A, Naskar B, Singha J, Chaterjee G. Music box spine keratoderma without any systemic manifestation. Indian Dermatol Online J
4. Torres G, Behshad R, Han A, Castrovinci AJ, Gilliam AC. ‘I forgot to shave my hands’: a case of spiny keratoderma. J Am Acad Dermatol
5. Nagler A, Boyd KP, Patel RR, Lee HS. Spiny keratoderma. Dermatol Online J
6. Grillo E1, Pérez-García B, González-García C, Vano-Galván S, Jaén-Olasolo P. Spiky keratotic projections on the palms and fingers. Spiny keratoderma. Dermatol Online J
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7. Yukawa M, Satoh T, Higuchi T, Yokozeki H. Spiny keratoderma of the palms successfully treated with topical tacalcitol. Acta Derm Venereol