Lichen myxedematosus: diagnostic criteria, classification, and severity grading

Background Lichen myxedematosus (LM) is a rare, chronic idiopathic disorder characterized clinically by waxy, closely set papules and histopathologically by diffuse dermal mucin deposition and fibroblast proliferation. The most recent classification of LM was proposed in 2001; however, it seems to be complex, confusing, and imprecise. Herein, we present seven cases of LM to evaluate the validity of the current classification, to propose new diagnostic criteria and classification, and to suggest a clinically relevant severity grading system for this rare disorder. Materials and methods The study included seven patients with different presentations and severities of LM. All patients were subjected to thorough dermatological and systemic examination, routine laboratory tests, evaluation of thyroid function, protein electrophoresis, and detailed investigations to detect systemic involvement. Results The current classification does not meet the requirements of proper diagnosis of different presentations of LM. Subtyping of the studied patients differs greatly according to the old classification and the newly proposed one. New diagnostic criteria, classification, and grading are consequently suggested. Conclusions We propose two sets of diagnostic criteria to define the disease more precisely and to avoid confusion associated with the other classification. The first set comprises constant clinical and histopathological features that are always present in every case, and the second set includes associated features that were variably reported in some patients. LM is then subclassified according to the presence or absence of systemic manifestations into a systemic severe form (scleromyxedema) and a non-disabling, pure cutaneous form.