Clinical significance of umbilical region involvement in pemphigus vulgaris in a series of 81 ethnic Poles: a comparative analysis of the distribution of lesions in two infrequent locations - Jałowska, Magdalena; Gornowicz-Porowska, Justyna; Seraszek-Jaros, Agnieszka; Bowszyc-Dmochowska, Monika; Kaczmarek, Elżbieta; Dmochowski, Marian (Advances in Dermatology and Allergology/Postępy Dermatologii i Alergologii, 2022)