MUC5AC and systemic mastocytosis: For the positive diagnosis of SM, Rongioletti and Rebora proposed the following criteria in 2001 [4]: (i) A clinical examination of a generalized papular and sclerodermoid eruption, (ii) A cutaneous histological examination revealing mucin deposits in the reticular dermis, fibroblastic proliferation, and fibrosis, (iii) The presence of serum monoclonal gammopathy, and (iv) The absence of thyroid pathology.