A novel ATP2C1 early truncation mutation suggests haploinsufficiency as a pathogenic mechanism in a patient with Hailey-Hailey disease.

Hailey-Hailey disease (HHD, MIM 16960) is an autosomal dominant disease characterized by suprabasal cell separation (acantholysis) of the epidermis. The clinical features vary and include crusted erosions with vesicular pustules, and erythematous scaly plaques at sites of friction and flexures. The skin lesions are often exacerbated by heat, sweating, mechanical trauma, infection and exposure in ultraviolet B (UVB) (1). Patients have a defect in ATP2C1 encoding the ATPase, Ca2+-transporting, type 2C, member 1; (ATP2C1) on the Golgi apparatus (2). We performed mutation analysis of ATP2C1 in a Japanese patient with HHD and identified the heterozygous novel mutation c.212delT (p.Leu71ArgfsX26). This is a very early truncating mutation, which clearly suggests that haploinsufficiency is an underlying patho­ mechanism of HHD.