Flesh-Colored Lesions With a Central, Horny Spine

A 3-year-old boy presented with an asymptomatic skin eruption on his upper arms and trunk. The eruption, which had appeared suddenly during late infancy, had progressively become worse. He had had no previous therapy for the eruption. The patient had atopic dermatitis but was otherwise in good health. A review of systems showed no abnormalities, and there was no family history of similar skin lesions.

Physical examination showed symmetrical plaques of numerous discrete, keratotic follicular papules on the trunk and upper arms. The individual lesions were flesh-colored, 1 to 2 mm in diameter, and consisted of a central horny spine. On palpation, the papules had a nutmeg grater-like consistency. Eczematous lesions were noted in the antecubital and popliteal areas. The rest of the physical examination was unremarkable. 

What’s your diagnosis?

(Answer and discussion are on the next page.)

ANSWER: Lichen spinulosus 

Lichen spinulosus is a dermatosis characterized by follicular keratotic spiny papules that are grouped into large symmetrical plaques.¹ This disorder was first described by Crocker in 1883, and the term “lichen spinulosus” was coined by Adamson in 1905.²  

EPIDEMIOLOGY 

The exact incidence of lichen spinulosus is not known, as there is a paucity of literature on this condition. It is considered uncommon. One study of 7435 patients examined and treated in a dermatology clinic in the Philippines found that 35 (0.47%) patients were diagnosed as having lichen spinulosus.³As the studied patients were highly selected, the result may not be applicable to that of the general population. Lichen spinulosus is most often seen in children, adolescents, and young adults.^1,3,4
There is a male predominance,^1,3,4 but the condition occurs in all races and there is no predilection in any ethnic group.^1,5 The majority of cases are sporadic, but familial cases have rarely been reported.⁶

ETIOLOGY

In the majority of cases, the etiology is idiopathic. The condition is more common in patients with atopy.^5,7,8 In some cases, there is a genetic predisposition.⁶ Lichen spinulosus has been reported to follow the administration of arsphenamine, omeprazole, sodium thiosulfate, thallium, gold, and diphtheria toxin.^5,9 Some cases are secondary to infections such as HIV infection, in reaction to fungal infection, Crohn disease, Hodgkin disease, and chronic alcoholism.^10-12

HISTOPATHOLOGY 

Histopathologic features include dilated hair follicles filled with a keratotic plug and perifollicular lymphocytic infiltrate in the dermis.⁵ Hyperkeratosis, parakeratosis, and acanthosis may be present in the follicles.⁵

CLINICAL MANIFESTATIONS 

The onset of lichen spinulosus is usually sudden. The lesions may appear simultaneously or in crops.³ Characteristic lesions are flesh-colored, hyperkeratotic follicular papules, 1 to 3 mm in diameter, with a central, hair-like, horny spine that extends approximately 1 to 2 mm above the surface.^1,3 The lesions feel like a nutmeg grater.³ The papules are grouped into plaques measuring 2 to 5 cm in diameter, and affected areas are frequently symmetrical.⁵ Sites of predilection are the trunk and extremities, including the neck, extensor surfaces of the arms, abdomen, buttocks, trochanters, and knees.^1,5 The hands, feet, and face are usually spared.¹¹ Occasionally, the lesions can be generalized, especially in patients with an underlying disorder.^10,11 The lesions are usually asymptomatic but may be mildly pruritic.⁷

DIAGNOSIS

The diagnosis is mainly clinical based on its typical features. Histologic examination and/or referral to a dermatologist should be considered if the diagnosis is in doubt.

DIFFERENTIAL DIAGNOSIS 

The main differential diagnosis is keratosis pilaris, which typically presents as minute, discrete, keratotic, follicular papules with variable perifollicular erythema.^13,14 Keratosis pilaris is distinguished by its much more common occurrence, slower rate of development, perifollicular erythema, predilection for the lateral aspects of the arms and thighs, and the possibility of the entire individual lesion being removed with the plug.^3,13,14 In contrast, the horny spine of lichen spinulosus can be removed, leaving a tiny, funnel-like orifice in the papule.^1,3 The other differential diagnoses include lichen nitidus, frictional lichenoid eruption, drug eruption, lichen striatus, lichen sclerosis, Darier disease (keratosis follicularis), Gianotti-Crosti syndrome, pityriasis rubra pilaris, phrynoderma (hypovitaminosis A), follicular mucinosis, miliary papular syphilis, lichen scrofulosorum, multiple minute digitate hyperkeratosis, and trichophytids.^1,5,15

PROGNOSIS

In the majority of cases, there is no associated systemic disorder. However, the condition is often considered cosmetically unsightly.⁵ The course is variable, with spontaneous resolution in some cases, especially during adolescence.¹ Other lesions may persist with a relapsing-remitting course.^4,5

MANAGEMENT 

The lesions are benign and asymptomatic. Therefore, except for cosmesis, no treatment is necessary. If treatment is desired for cosmesis, emollient keratolytics (lactic acid, urea, salicylic acid gels/creams/ointments) have been used with success in this regard.¹ Topical retinoids or vitamin D analogues are potential alternatives.^7,8,16 An underlying disorder, if present, should also be treated.  

Alexander K. C. Leung, MD, is a clinical professor of pediatrics at the University of Calgary and a pediatric consultant at the Alberta Children’s Hospital in Calgary, Alberta, Canada. 

Benjamin Barankin, MD, is a dermatologist and the medical director and founder of the Toronto Dermatology Centre in Toronto, Ontario, Canada.

REFERENCES

1. Tilly JJ, Drolet BA, Esterly NB. Lichenoid eruptions in children. J Am Acad Dermatol. 2004;51(4):606-624.

2. Adamson HG. Lichen pilaris, seu spinulosis. Br J Dermatol. 1905;17:39-54.

3. Friedman SJ. Lichen spinulosus. Clinicopathologic review of thirty-five cases. J Am Acad Dermatol. 1990;22(2 Pt 1):261-264.

4. Venkatesh A, Dupuis E, Prajapati V, et al. Generalized lichen spinulosus in a 4-year-old boy without systemic disease. Arch Dermatol. 2012;148(7):865-866.

5. Boyd AS. Lichen spinulosus: case report and overview. Cutis. 1989;4(6)3:557-560.

6. Meyer D, Stolp A, Knapp A. Uber eine Famillie mit Keratosis follicularis spinulosa bei vermutlich dominantem Erbgang. Dermatol Wochenschr. 1965;151:201-206. 

7. Kim SH, Kang JH, Seo JK, Hwang SW, Sung HS, Lee D. Successful treatment of lichen spinulosus with topical tacalcitol cream. Pediatr Dermatol. 2010;27(5):546-547.

8. Uehara A, Abe M, Shimizu A, et al. Successful treatment of lichen spinulosus with topical adapalene. Eur J Dermatol. 2015;25(5):490-491.

9. Lee ML, Piper DW, Fischer GO, De Launey WE. Lichen spinulosus after the ingestion of omeprazole. Med J Aust. 1989;150(7):410.

10. Cohen SJ, Dicken CH. Generalized lichen spinulosus in an HIV-positive man. J Am Acad Dermatol. 1991;25(1):116-118.

11. Kabashima R, Sugita K, Kabashima K, et al. Lichen spinulosus in an alcoholic patient. Acta Derm Venereol. 2009;89(3):311-312. 

12. Kano Y, Orihara M, Yagita A, Shiohara T. Lichen spinulosus in a patient  with Crohn’s disease. Int J Dermatol. 1995;34(9):670-671.

13. Leung AK, Robson WL. Keratosis pilaris. In: Lang F, ed. The Encyclopedia of Molecular Mechanisms of Disease. Berlin, Germany: Springer-Verlag; 2009:1119-1120.. 

14. Leung AK, Kao CP. Small, red papules in a 17-year-old girl. Consultant. 2011;51(2):104-106.

15. Comert A, Akin O, Demirkesen C. Follicular mucinosis mimicking lichen spinulosus. Eur J Dermatol. 2007;17(6):544-545.

16. Forman SB, Hudgins EM, Blaylock WK. Lichen spinulosus: excellent response to tretinoin gel and hydroactive adhesive applications. Arch Dermatol. 2007;14(1):122-123.