P02 Galli Galli disease: a rare variant of the genodermatosis Dowling–Degos disease

Abstract A 35-year-old woman presented with a 4-year history of a persistent pruritic rash affecting her upper and lower limbs, concerning to the patient for cosmetic reasons. She denied any precipitating factors and reported no improvement with the use of topical clobetasol propionate. Notably, her mother had a similar rash, which had also developed in her 30s and continued to progress over time. Physical examination revealed a bilateral symmetrical papular eruption with superficial scale affecting extensor surfaces of her upper and lower limbs. The patient’s mother was also reviewed and had similar clinical findings, although a more generalized distribution was noted. Skin biopsy from the right thigh of the daughter showed acantholysis in the stratum spinosum with dyskeratotic cells. Biopsy from the left thigh of the patient’s mother showed elongation of rete ridges with foci of increased basal pigmentation and intraepidermal acantholysis. The presence of acantholysis and elongation of rete ridges with basal pigmentation histologically confirmed the diagnosis of the Galli–Galli variant of Dowling–Degos disease (DDD). The genetic basis for DDD involves a heterozygous loss of expression mutation affecting KRT5. Other implicated mutations include POGLUT1, POFUT1 and PSENEN, which are important in melanosome transfer, and the differentiation of melanocytes and keratinocytes. Galli–Galli disease remains a therapeutic challenge. Reported treatments trialled include topical retinoids, oral corticosteroids, and narrowband ultraviolet, although the outcomes have been disappointing. Successful treatment with erbium : yttrium aluminium garnet laser has been reported. Owing to the progressive nature of this condition, patient counselling regarding treatment expectations is important.