Psoriatic alopecia

Summary Alopecia and other hair abnormalities occurring in patients with psoriasis were first recognized over four decades ago, yet psoriatic alopecia is not a well‐known concept among clinicians. Alopecia may be directly related to the psoriasis itself, and can affect both the scalp and other parts of the body. On the scalp, psoriatic alopecia most commonly affects lesional skin, but may present as a generalized telogen effluvium. In most cases, there is regrowth of hair, but in rare cases it can cause scarring alopecia. Histological findings include features of psoriasis in the interfollicular epithelium, along with perifollicular inflammation and atrophy or loss of the sebaceous glands. Late changes include destruction of the hair follicle, with perifollicular fibrosis and ‘naked’ hair shafts lying free in the dermis. In addition to the hair loss caused by the psoriasis itself, data from population and genetic studies reveal that patients with psoriasis are at greater risk of developing alopecia areata. Psoriasis treatments may also contribute to hair loss. Application of topical preparations may cause hair loss through friction, and many of the systemic treatments used for psoriasis can also cause hair problems. Treatment with anti‐tumour necrosis factor‐α agents can precipitate de novo psoriasis and subsequent psoriatic alopecia.