[Lack of therapeutic response: Is it really a rheumatoid Arthritis?].

Anamnesis: A 78-year-old female patient was referred to our hospital with treatment-resistant seronegative anti-citrullinated protein antibodies (ACPA)-negative rheumatoid arthritis. The course was characterized by high inflammatory activity and rapid progression of the erosive changes. Under the required high-dose prednisolone therapy, osteoporosis and a deep venous thrombosis (DVT) with pulmonary embolism developed.