Current Issue

Spring/Summer 2025, Vol. 32 No. 1

Hong Kong J. Dermatol. Venereol. (2025) 32, 61-65

Case Report

Spiny keratoderma: a case report and literature review

棘狀角皮病：病例報告及文獻回顧

Abstract

Spiny keratoderma is a non-malignant cutaneous condition that affects the palms and/or soles. The clinical presentation is with those of multiple tiny firm and hyperkeratotic projections resembling the spines of an old-fashioned music box. There have been more than 42 cases reported in literature. This is the first case report of spiny keratoderma in Hong Kong.

棘狀角皮病是一種影響手掌和/或腳底的非惡性皮膚病。臨床表現是多個微小、堅硬且角化過度的突出物，類似於音樂盒的突刺。文獻中報告的病例現時已超過42例。這是本港首宗棘狀角皮病個案報告。

Keywords: Music-box keratoderma, Palmoplantar spines, Spiny keratoderma, Wood's light

關鍵詞: 音樂盒角化病、手掌腳底突刺、棘狀角皮病、螢光反應檢驗燈(伍氏燈)

Introduction

Spiny keratoderma, also known as music box keratoderma, is rare skin condition characterised by small, hard, spine-like projectins or spicules on the palms and/or soles. The first case of spiny keratoderma was presented by Brown in 1971.¹ He described a 20-year-old man presenting with numerous tiny spicules on the palmoplantar surface in which biopsy showed columns of well-defined parakeratotic material arising from the malpighian layer with a little granular layer. He named it as punctate keratoderma. There have been more than 42 cases reported in literature since then.²

Case report

A 76-year-old man complained of numerous tiny rough 'spines' over his palms and fingers since age 50. It was asymptomatic. His soles were not affected. There was no family history of similar problem. He was born in China. He reported a history of well water consumption. He used to work as a carpenter until his retirement. His past medical history included hyperlipidaemia and benign prostatic hypertrophy, which were controlled by simvastatin and prazosin respectively.

Physical examination revealed multiple tiny keratotic spiky projections over both palms and volar surfaces of all fingers (Figure 1a & 1b). Both feet were normal. The projections excited white fluorescence under Wood's light like 'stars in the moonlight' (Figure 1c & 1d).

Figure 1 Clinical features of the spiny lesions.

A 3 mm punch biopsy was performed for one of the "spines" on the left palm. Histopathology showed a column of compact parakeratosis with underlying hypogranulosis but no dyskeratosis or vacuolar degeneration. The column was sharply demarcated from the adjacent orthokeratotic stratum corneum (Figures 2-4). Both clinical features and histopathology were compatible with the clinical diagnosis of spiny keratoderma.

Figure 2 A compact column of hyperparakeratosis sharply separated from adjacent orthokeratotic stratum corneum.

Figure 3 Underneath hypogranulosis and slightly depressed epidermis.

Figure 4 No dyskeratosis or vacuolar degeneration.

Malignancy screening and systemic review were performed. Blood tests including complete blood count, liver and kidney function tests, tumour markers (Carcinoembryonic antigen, Prostate-specific antigen and Alpha-fetoprotein), and serum paraprotein electrophoresis were all normal. The stool for occult blood was negative. Computed tomography of the thorax abdomen and pelvis revealed nonspecific tiny lung nodules only.

He was given different topical treatments including 10% urea cream, 2% salicylic acid, 0.1% Adapalene gel, and 0.01% Tretinoin cream, but all were ineffective. Mechanical debridement with a nail clipper provided temporary relief and the spines soon returned. Wood's light examination after nail clipping showed less 'spines' (Figure 5). Oral Acitretin was declined by the patient. Expectant management was opted.

Figure 5 'Stars in the moonlight' appearance under Wood's light.

Discussion

Terminology Myriads of names have been used to describe this clinical condition.^3-7 These include "punctate porokeratotic keratoderma'', "porokeratosis punctate palmaris et plantaris", "punctate porokeratosis", "filiform hyperkeratosis", "multiple minute palmar-plantar digitate hyperkeratosis", "punctate keratosis of the palms and soles'' and "music box keratoderma". However, all these names are not only imprecise but also confusing. In 1992, Osman et al⁸ first coined the term "Spiny Keratoderma'' with the fact that these spiny lesions should not be classified as a porokeratosis because of its distinct histo-morphology from porokeratosis, and a lack of malignant potential. The term spiny keratoderma was deemed to be more appropriate.

Clinical features Apart from a feeling of roughness, the lesions of spiny keratoderma are asymptomatic.² It affects palms and/or soles, but isolated plantar involvement has never been reported.⁹ For hereditary cases, the age of onset is 15-50 years. Males are predominantly affected. It runs in an autosomal dominant inheritance pattern. There is no racial predilection, and the condition is not associated with any malignancy or systemic diseases. In contrast for the acquired cases, the age of onset is mostly in the fifth decade with male predominance. These are associated with malignancy or systemic diseases. Malignancy is reported in up to 50% of cases in the literature,⁹ including haematological malignancies, malignant melanoma or solid organ carcinomas. Several systemic diseases such as type IV hyperlipoproteinaemia, chronic renal failure, adult-onset polycystic kidney disease and pulmonary tuberculosis have been reported before.

Differential diagnoses The major differential diagnoses of spiny keratoderma include multiple filiform verrucae, arsenical keratosis, punctate porokeratosis and hereditary punctate palmoplantar keratoderma (type 1, 2 or 3).

Histological features The distinct histological feature of spiny keratoderma¹⁰ is a compact column of parakeratosis with an underlying hypogranulosis, which is sharply demarcated from the adjacent orthokeratotic stratum corneum. There is no dyskeratosis or vacuolisation underneath the keratotic column.

Causes The aetiology of spiny keratoderma can be idiopathic, hereditary or acquired. Most of the cases are idiopathic. In a recent review of 37 cases of spiny keratoderma,⁹ 16% are hereditary with autosomal dominant inheritance. In comparison, 27% (10 cases) have been associated with malignancies which included myelofibrosis, malignant melanoma, chronic lymphoid leukaemia, lung cancer, oesophageal cancer, gingival squamous cell carcinoma, multiple myeloma and colonic cancer. Four of them had a history of malignancy preceding the development of spiny keratoderma, while three were newly diagnosed to have malignancy from the cancer screening during the workup of spiny keratoderma. In only one of these patients, the spines completely regress after treatment of the underlying malignancy. Hence a solid association with malignancy cannot be established with certainty. Association with systemic disease is also postulated. In the same review, six patients with spiny keratoderma diagnosed were found to have a significant history of manual labour, hypertension and hyperlipidaemia treated with statin. However, these 'associated conditions' are commonly shared within the general population. Therefore, it is difficult to ascertain if there are genuine causal relationships.

Use of Wood's lamp One study demonstrated white fluorescence of the 'spines' upon Wood's light examination resembling stars under the moonlight.¹¹ The exact mechanism responsible for that observation remains unclear. The role of Wood's lamp in diagnosing spiny keratoderma is also uncertain. However, the use of Wood's light helps determine the extent of the disease and is highly useful in monitoring the disease's progress.

Management There is no established treatment yet. Several treatment modalities have been reported,¹² and these are broadly classified into mechanical debridement, topical treatment and oral treatment. Mechanical methods include paring, dermabrasion or shaving with a razor blade. Topical treatments like 0.1% Tazarotene gel 0.1%, 0.05% Tretinoin, urea cream, 5% 5-fluorouracil cream, 0.002% Tacalcitol ointment, 5% ammonium lactate lotion, 6% salicylate gel and 50% salicylate acid in petroleum followed by curettage have been used with some success. Oral Acitretin 25 mg-30 mg per day has been reported in case reports for its success in treating spiny keratoderma.¹³ All in all, spiny keratoderma is difficult to treat, and the therapeutic outcome is unsatisfactory. Recurrence upon treatment cessation is not uncommon.

Conclusion

Spiny keratoderma is a rare chronic condition. Multiple keratotic spicules over palms and/or soles are characteristic. Hereditary cause should be considered for young onset disease, while malignancy or associated systemic conditions have to be excluded in the acquired cases that present after the fifth decade. Age-appropriate malignancy screening is widely recommended by different authors although the causal relationship with malignant neoplasm elsewhere has not been firmly established. Treatment outcome is mostly suboptimal, and recurrence is the rule rather than the exception. The use of Wood's light examination is extremely helpful in determining the extent of the disease and monitoring the disease progress.

References

1. Brown FC. Punctate keratoderma. Arch Dermatol 1971;104:682-3.

2. Dokic Y, Tschen J. Spiny Keratoderma of Nonfamilial Nature and Without Systemic Disease in a Woman. Cureus 2019;11:e5609.

3. Herman PS. Punctate porokeratotic keratoderma. Dermatologica 1973;147:206-13.

4. Lestringant GG, Berge T. Porokeratosis punctata palmaris et plantaris: A new entity? Arch Dermatol 1989;125:816-9.

5. Mehta RK, Mallett RB, Green C, Rytina E. Palmar filiform hyperkeratosis (FH) associated with underlying pathology? Clin Exp Dermatol 2002;27:216-9.

6. Guarneri C, Guarneri F, Vaccaro M, Borgia F, Cannavò SP. Multiple minute digitate hyperkeratoses. Int J Dermatol 2005;44:664-7.

7. Sakas EL, Gentry RH. Porokeratosis punctata palmaris et plantaris (punctate porokeratosis): Case report and literature review. J Am Acad Dermatol 1985;13:908-12.

8. Osman Y, Daly TJ, Don PC. Spiny keratoderma of the palms and soles. J Am Acad Dermatol 1992;26:879-81.

9. Chee SN, Ge L, Agar N, Lowe P. Spiny keratoderma: case series and review. Int J Dermatol 2017;56:915-9.

10. Apurwa A, Desai C, Agarwal S, Patil S. Spiny keratoderma: The gritty tale. Indian Journal of Dermatopathology and Diagnostic Dermatology 2018;5:124-6.

11. Erkek E, Atasoy P. Fluorescence of hereditary type II punctate porokeratotic keratoderma (spiny keratoderma) with a Wood's light: stars under the moonlight. J Am Acad Dermatol 2007;57:S63-4.

12. Schweitzer J, Koehler M, Horowitz D. Idiopatic spiny keratoderma: A report of two cases and literature review. Jaocd 2014;14:30-2.

13. Scott‐Lang VE, McKay DA. Spiny keratoderma successfully treated with acitretin. Clin Exp Dermatol 2013;38:91-2.