Keratosis follicularis spinulosa decalvans

Keratosis follicularis spinulosa decalvans (KFSD), also known as Siemens syndrome or keratosis pilaris decalvans, is a rare inherited skin disorder belonging to the group of keratosis pilaris atrophicans conditions. It primarily affects the hair follicles, leading to widespread follicular hyperkeratosis (rough, spiny bumps around hair follicles), progressive scarring alopecia (permanent hair loss) of the scalp, and loss of eyebrows and eyelashes. The condition typically begins in infancy or early childhood with keratosis pilaris-like lesions on the face and body, followed by progressive cicatricial alopecia of the scalp that worsens over time. KFSD predominantly affects the skin, hair, and eyes. Ocular involvement is common and may include photophobia (light sensitivity), blepharitis, and corneal dystrophy. The follicular keratotic papules can be widespread, affecting the face, neck, trunk, and extremities. Males tend to be more severely affected than females, consistent with the X-linked inheritance pattern. The condition is caused by mutations in the MBTPS2 gene (also known as SAT-1), located on the X chromosome, which encodes a membrane-bound transcription factor protease involved in cholesterol and fatty acid metabolism. There is currently no cure for KFSD. Treatment is symptomatic and supportive. Topical keratolytics (such as urea-based creams or salicylic acid) and emollients may help manage the follicular hyperkeratosis. Topical or oral retinoids have been used with variable success to reduce keratotic lesions, though they do not prevent progressive hair loss. Anti-inflammatory treatments may help manage scalp inflammation. Ophthalmologic monitoring is recommended for patients with eye involvement. Early dermatologic and genetic counseling is advised for affected families.

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