<i>ATP2C1</i>-nonsyndromic epidermal differentiation disorder, also known as familial benign chronic pemphigus or Hailey-Hailey disease, is a rare autosomal dominant acantholytic disorder characterized by relapsing and remitting painful vesicles and erosions in flexural areas. The gene discussed is ATP2C1; the disease is Familial benign chronic pemphigus.