Substance P in keratosis follicularis spinulosa decalvans

KFSD: Keratosis folicularis spinulosa decalvans SP: Substance P INTRODUCTION Keratosis follicularis spinulosa decalvans (KFSD) is an inherited rare disorder characterized by diffuse keratosis pilaris and scarring alopecia. Palmoplantar keratoderma, ocular abnormalities, and atopy can also be present. Most cases occur in males and have a X-linked pattern of inheritance, although autosomal dominant and sporadic cases have been reported. The pathogenesis of this intriguing disease is not well understood. Substance P (SP), an important marker of neurogenic inflammation, is widely distributed in the central and peripheral nervous systems. In the skin, SP-positive nerve fibers can be normally present in the dermis and epidermis. SP is considered a potent neuropeptide vasodilator and has been associated with many inflammatory processes, such as mast cell degranulation and neutrophil/lymphocyte chemotaxis. SP can also lower itch thresholds and stimulate fibrosis and healing processes through fibroblast activation. Increased levels of SP have been reported in many inflammatory skin conditions, including alopecia areata, atopic dermatitis, and psoriasis. We describe a Brazilian girl with a generalized severely pruritic scalp and typical features of KFSD whose lesional skin scalp showed increased levels of the neuropeptide SP. To our knowledge, this is the first time this neuropeptide is reported in the setting of KFSD.