Is this still just sarcoidosis, or should we a-DRESS a different diagnosis?

An Afro-Caribbean woman presented with worsening breathlessness, weight loss, lethargy and fevers, developing a bilateral florid erythematous rash on her legs. She was recently diagnosed with rheumatoid arthritis and bilateral hilar lymphadenopathy was found on thoracic CT imaging. She was tachycardic and investigations revealed pancytopenia, eosinophilia, raised serum ACE, acute kidney injury and deranged liver function tests. Biopsy of the lymphadenopathy revealed mixed lymphoid cells and liver biopsy revealed extramedullary haematopoiesis, with hypercellular marrow found on bone marrow biopsy. Cardiac MRI was normal, excluding cardiac sarcoid. The patient developed status epilepticus and phenytoin was started. She subsequently developed skin desquamation, in keeping with toxic epidermal necrosis. Skin biopsies revealed atypical granulomas and multinucleated giant cells, which subsequently resolved on steroid treatment. This case highlights an overlap syndrome, with an unclear diagnosis between sarcoidosis, drug reaction or rash with eosinophilia and systemic symptoms and/or hypereosinophilic syndrome and Still's disease. Hence varied serological and clinical features can complicate the distinction between diagnoses.