The patient was diagnosed with lichen spinulosus (LS) based on the physical appearance of the lesions (hyperkeratotic spiny papules forming plaques), the lack of pruritus, and negative personal history of atopic dermatitis.
Lichen spinulosus is an underreported entity, first described in 1908 by Adamson as superficial circumscribed chronic dermatitis in children and adolescents. The median age of presentation is age 16 years. There are several reports of possible associations with systemic infections such as HIV, fungi, and syphilis, as well as chronic diseases such as Crohn’s disease, Hodgkin disease, seborrhea, and secondary to certain medications such as omeprazole. There are no prior reports of infliximab being associated with LS, but it has been reported to cause other lichenoid reactions such as lichen planus and lichen planopilaris.
Clinically the lesions are characterized by asymptomatic, small (1 cm), skin color, hyperkeratotic, follicular papules that coalesce into plaques. The lesions usually occur on the extensor surfaces of the arms, neck, torso, and buttocks. Mild pruritus can occur in some patients.
The lesions in keratosis pilaris can be very similar to lichen spinulosus, but usually they don’t coalesce into plaques and are commonly present on the extensor surfaces of the arms, thighs, and cheeks. Histopathology of both conditions is very similar.
Another condition to consider includes papular eczema. The lesions in papular eczema tend to be pruritic and are not as circumscribed as LS lesions. Papular eczema responds well to the use of topical corticosteroids, while LS lesions usually do not. Lichen nitidus (LN) is characterized by monomorphic, skin color, 1-mm, flat-topped papules. Lesions tend to occur in crops rather than circumscribed papules forming plaques. LN most commonly presents on the extensor surface of the arms, trunk, dorsal hands, and genitalia. Koebner phenomenon is usually seen. Although uncommon in children, a more generalized type of follicular mucinosis can present very similar to lichen spinulosus. A recent study found LS-like lesions with associated hypopigmentation and hair loss should be suspicious for folliculotropic mycosis fungoides.
Keratolytics such as lactic acid, urea, and salicylic acid can help improve LS, although they do not cure it. Other reported treatments include the use of topical adapalene, tacalcitol cream, and tretinoin gel with hydroactive adhesive.
Dr. Matiz is a pediatric dermatologist at Southern California Permanente Medical Group, San Diego. Email her at.