Tuberculosis (TB) isa major global public healthconcern. The extrapulmonary manifestations ofTB can bemisleading and challenging todiagnose.Thoracic cold abscessis a rare and unusualentity of TB.Itrepresents 1-5% of musculoskeletal localisations of TB and constitutes a differentialdiagnosiswithpyogenicabscess, slow-growingpathogens or walltumours. In endemic areas, anypainless progressive abscessshouldsuggest a tuberculosis infection. Despite the clear diagnostic contribution of molecularbiologywith the Xpert MTB/Rif, a positive culture on a sample of fluid or tissue remains the gold standard. The management of tuberculousthoracicabscessiscontroversial and the combination of standard chemotherapy and surgeryseems to be the mostappropriate. Hereinwe report a case of a cold thoracicabscess in a 35-year-old man with no previoushistory.

Erdheim-Chester disease (ECD) is a rare form of non-Langerhansian histiocytosis classified by WHO since 2016 as a group L hematological neoplasia. Its pathophysiology is very complex and its multi-systemic character explains the plurality of clinical-radiological presentations. Bone involvement is almost constant while associated lung involvement is found in 50% of cases with non-specific clinical signs such as dyspnea and cough. Imaging provides an undeniable diagnostic contribution but confirmation of ECD is based on histopathology with immunohistochemical study. The search for the BRAF mutation by molecular biology has innovated the therapeutic management.The aim of our report is to relate a rare case of Erdheim-Chester disease in a 40-year-old man with an atypical pulmonary pseudotumor presentation without bone involvement and the diagnosis difficulty faced. Reporting of this type of aggressive disease should have an impact on early diagnosis and better prognosis.