BH13: Scarring alopecia affecting a congenital melanocytic naevus in a patient with frontal fibrosing alopecia

Sarah Drummond,¹ Lucy Melly² and Susan Holmes¹

¹Department of Dermatology, Glasgow Royal Infirmary; and ²Department of Pathology, Queen Elizabeth University Hospital, Glasgow, UK

A 52-year-old woman was referred to dermatology for review of a long-standing melanocytic naevus on her right forearm. A clinical diagnosis of a benign congenital melanocytic naevus with focal hypertrichosis was made. The patient was referred 5 years later with loss of eyebrows and recession of the frontal hairline. The clinical features were those of frontal fibrosing alopecia (FFA). The hypertrichosis noted previously within the congenital melanocytic naevus had largely disappeared. The lesion was excised and histology confirmed a benign compound melanocytic naevus. Within the naevus, there was loss of hair follicles and replacement with scarring. Remaining hair follicles showed perifollicular fibrosis and chronic inflammation with interface activity affecting the follicular epithelium. The appearances were consistent with a lichenoid scarring alopecia. FFA is a form of scarring alopecia typically causing band-like recession of the frontotemporal hairline and loss of eyebrows. Noninflammatory loss of limb hair is also common, reported in 45–77% of cases in several large cohorts. (McSweeney SM, Christou EAA, Dand N et al. Frontal fibrosing alopecia: a descriptive cross-sectional study of 711 cases in female patients from the UK. Br J Dermatol 2020; 183: 1136–8). Histology of limb hair loss in patients with FFA shows similar features to the affected scalp, including a marked reduction in the number of hair follicles and perifollicular lichenoid infiltrate. (Chew AL, Bashir SJ, Wain EM et al. Expanding the spectrum of frontal fibrosing alopecia: a unifying concept. J Am Acad Dermatol 2010; 63: 653–60). Perifollicular fibrosis and follicular scarring have been demonstrated in some studies (Chew et al.). Histology in our case demonstrated both follicular scarring and perifollicular fibrosis. This loss of focal hypertrichosis in a congenital melanocytic naevus in a patient with FFA has not been reported previously. The clinical changes are striking and histology confirms a lichenoid scarring alopecia.