Spiny keratoderma of the palms and soles – report of two cases

ARTICLE

Spiny keratoderma of the palms and soles is a rare disorder consisting of multiple tiny keratotic plugs, resembling the spines on a music box, on the palms and soles.

Histopathologically, the lesions show compact columns of parakeratosis with a reduced to absent granular layer beneath the column. Only 27 cases of spiny keratoderma of the palms and soles have been reported in the literature [1-20]. It is important to recognize that the disease is associated with internal malignancies [2, 5, 9, 14, 16, 18]. We report two cases of spiny keratoderma of the palms and soles.

Case report

Case 1: An 85-year-old woman who had been admitted to Tokoname Municipal Hospital, Tokoname, Japan, for treatment of a fracture of the right femoral neck was referred to us because of multiple asymptomatic, keratotic papules on her palms and soles. The patient could not state precisely the date of onset of the lesions owing to senile dementia. On physical examination, she had spiny and filiform horny projections strictly limited to both volar surfaces of the fingers and toes, palms and soles (Fig. 1). The individual keratotic lesions were white to skin-colored, about 1 mm in diameter and 0.5 ~ 1.0 mm in length. The base was firmly attached to the underlying skin. In some places there were tiny shallow pits. There were no hair, teeth nor bony abnormalities. She had no history of hyperhidrosis or hypohidrosis and was unaware of any exposure to arsenic. She had a more than 20-year history of hypertension and hypertrophy of the left ventricle. The hypertension had been treated with nifedipine. She was a rice cake maker.

Histopathological examination of skin biopsy specimens of the palm and sole showed that each spiny keratotic projection consisted of a single, well-defined, compact column of parakeratotic horn material directly continuous with the granular layer. There was an abrupt transition to the orthokeratotic corneal layer at the margins of the parakeratotic column (Fig. 2A). No dyskeratotic or vacuolated keratinocytes were seen in the underlying epidermis (Fig. 2B). In the specimen obtained from the sole, the papillary dermis showed a mild perivascular inflammatory lymphocytic infiltrate.

The garium scintigram was normal. Computerized tomographic scan suggested a tumor from the esophagus to cardia.

Her son, grandson and granddaughter had similar spiny hyperkeratosis. Her son had died of liver cirrhosis at the age of 60. Her 37-year-old grandson noted lesions at the age of about 20, and her 35-year-old granddaughter noted lesions at the age of about 30. They had lesions on both the fingers and palms, but none were found on the soles. They were in good general health and had no history of hyperhidrosis or hypohidrosis and were unaware of any exposure to arsenic.

Case 2: A 56-year-old man who had been admitted to Tokoname Municipal Hospital for treatment of an attack of bronchial asthma was referred to us because of multiple asymptomatic, keratotic papules on his fingers and palms. The patient had not noted the lesions before admission. He had experienced mild to moderate asthma attacks since the age of 52. This was the first severe attack. Tracheal intubation had been performed, with the institution of mechanical ventilation for three days. Seven days after extubation, he had noted the lesions. Examination revealed firm, keratotic spines strictly limited to both volar surfaces of the fingers and palms (Fig. 3). The individual keratotic lesions were white to skin-colored, about 0.5 mm in diameter and 0.5~1.0 mm in length. The base was firmly attached to the underlying skin. In some places there were tiny shallow pits. No other skin, dental nor bony abnormalities were found. He had no history of hyperhidrosis or hypohidrosis and was unaware of any exposure to arsenic. There was no relevant family history.

Histopathological examination of a skin biopsy specimen of the palm showed findings similar to those of case 1, but no inflammatory cells were noted in the underlying dermis.

Garium scintigram and computerized tomographic scan showed no abnormality.

Topical treatment with 20% urea was not successful in either case. But we did not try further treatment because the disorder was of little discomfort and was well tolerated.

Discussion

To date only a small number of cases of spiny keratoderma of the palms and soles have been reported in the literature. There are probably two reasons: 1) this disorder is uncommon and most dermatologists overlook it [19] ; 2) such patients do not go to the hospital because most cases are otherwise asymptomatic or cause minimal discomfort [8]. Horton et al. [19] reported that spiny keratoderma was the primary complaint in only two of their reported six cases; in all other cases, this was an incidental finding made by a dermatologist or referred by another division, as in our cases.

Spiny keratoderma of the palms and soles was first described in 1971 by Brown [1] under the name of "punctate keratoderma". Since then, these spiny lesions have been described as "punctate porokeratotic keratoderma (palmaris et plantaris)" [2, 7, 10, 14], "punctate porokeratosis (of the palms and soles)" [3, 4, 6], "porokeratosis punctate palmaris et plantaris" [8], "Palmar filiform or spiny hyperkeratosis" [15, 16], "Hyperkératose palmo-plantaire filiforme (French)" [5, 9, 18], "multiple minute digitate hyperkeratoses" [12]. Considerable confusion exists as to whether this is a punctate keratoderma or a porokeratosis variant [17]. More recently, the designation of "spiny keratoderma (of the palms and soles)" has gained favor [11, 13, 17, 19-21]. Hashimoto et al. [21] suggested that it is a disease of ectopic hair formation of the palms and soles according to an analysis with hair specific antikeratin antibodies and electron microscopy.

The palmoplantar keratodermas (PPKs) are a heterogenous group of disorders characterized by abnormal thickening of the palms and soles. Clinically, three distinct clinical patterns of PPK may be identified [22, 23]: 1) Diffuse PPK, which is characterized by an even, thick, symmetric hyperkeratosis over the whole of the palm and sole; this pattern is usually evident at birth or in the first few months of life. 2) Focal PPK, in which large, compact masses of keratin develop at sites of recurrent friction, principally on the feet although also on the palms and other sites; the pattern of calluses in this focal group may be either discoid or linear, with considerable intra-and interfamily variation. 3) Punctate PPK, in which multiple tiny "raindrop" keratoses involve the palmoplantar surface; they may involve the whole of the palmoplantar surface or be more restricted in their distribution. Spiny keratoderma of the palms and soles is included in punctate PPK.

Zarour et al. [24] have proposed a classification of this keratinization disorder on the basis of the clinical and histological features (Table I). In this classification, parakeratotic lesions were termed porokeratotic filiform hyperkeratosis and those with orthokeratosis, ortokeratotic filiform hyperkeratosis. According to this classification, our cases can be classified into palmoplantar porokeratotic filiform hyperkeratosis (Type I a).

Spiny keratoderma of the palms and soles is frequently associated with malignant neoplasms [2, 5, 9, 14, 16, 18]. As a rule, it cannot be considered as an actual paraneoplastic syndrome, since it often begins several years before the diagnosis of cancer and persists after its removal. Nevertheless, it is associated with a high risk of malignancies, and patients should be carefully examined to detect any underlying neoplasms [14]. Kaddu et al. [16] reported that two types of palmoplantar filiform hyperkeratosis probably exist: 1) a type of palmoplantar filiform hyperkeratosis associated with malignancy. 2) A "benign" type of palmoplantar filiform hyperkeratosis that includes hereditary variants, forms associated with other diseases such as Darier's disease, chronic renal failure, and idiopathic forms. The patient of case 1 was suspected of having a tumor from the esophagus to cardia by computerized tomographic scan, but further examination was refused by her family. The patient of case 2 was not found to have malignant neoplasms. The coexistence of spiny keratoderma and bronchial asthma may have been coincidental because there have been no reports of skin lesions associated with bronchial asthma.

Horton et al. [19] suggested that the disease is a relatively common under-reported dermatosis found most often in older patients with a history of manual labor. A past medical history of hypertension and hyperlipidemia treated with HMG-CoA reductase inhibitors was significant. Hypertension was seen in four and hyperlipidemia in three of their five reported cases in which the medical history could be obtained. Our case 1 had hypertension. Dermatologists should keep spiny keratoderma of the palms and soles in mind in daily clinical examinations and examine for the presence of unknown internal malignancies.

Article accepted on 29/06/00

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