[Lung involvement of pyoderma gangrenosum: Diagnostic and therapeutic discussion based on a case report and a targeted literature review].

INTRODUCTION Pyoderma gangrenosum (PG) is a rare, mainly dermatological condition, whose unusual and little-known lung involvement presents a diagnostic and therapeutic challenge. CASE REPORT A 66-year-old man, followed for 6 years for an IgA monoclonal gammopathy of undetermined significance and an initially cutaneous corticosteroid-dependent PG, received a pneumonectomy for a mass suspected of neoplasia, that turns out to be a PG pulmonary localisation. During successive pneumopathies, sometimes dyspneic and excavated, several hypotheses are discussed. Various infectious and immunological explorations, and various antibacterial/fungal or immunosuppressive therapies are conducted, to finally conclude to pulmonary and/or cutaneous recurrences of PG. The outcome at 14 months seems finally favourable with tofacitinib. CONCLUSION The recognition of cutaneous involvement of PG, which is essential for the diagnosis of its lung involvement, is probably the mirror of its evolution under treatment. Only multidisciplinary confrontation of reported cases will allow the elaboration of diagnostic and therapeutic recommendations.