COL17A1 and Junctional epidermolysis bullosa, Herlitz type: Biallelic variants in COL17A1 (OMIM 113811) are a well-documented cause of the recessively inherited, genetically heterogeneous mucocutaneous blistering condition junctional epidermolysis bullosa (JEB).9 JEB is genetically heterogeneous and characterised by erosions and blistering of the skin and mucous membranes, with cleavage at the basement membrane zone.