The "kick-off" position: a new sign for early diagnosis of complex regional pain syndrome in the leg.

BACKGROUND Polycythemia vera (PV) is a myeloproliferative neoplasm (MPN) characterized by erythrocytosis resulting from the clonal overproduction of hematopoietic cells in the bone marrow and is closely associated with mutations in the Janus kinase 2 (JAK2) gene. Ruxolitinib, a selective JAK1/JAK2 inhibitor used to treat MPNs, predisposes patients to opportunistic infections. Herein, we report the case of a patient with PV treated with ruxolitinib who developed disseminated tuberculosis mimicking metastatic cancer. CASE REPORT A 71-year-old woman presented with imaging findings suggestive of metastases, elevated tumor markers, and a negative interferon-γ release assay. The diagnosis was confirmed by bone biopsy and a positive sputum Mycobacterium tuberculosis polymerase chain reaction test. The patient improved with standard 4-drug antituberculous therapy. In a focused review of 35 published cases of tuberculosis occurring during ruxolitinib therapy for MPNs, disseminated disease accounted for 50% of cases, whereas PV was reported in only 3 cases. Ruxolitinib-induced immunosuppression can lead to false-negative interferon-γ release assay results, and several tumor markers, including soluble interleukin-2 receptor, neuron-specific enolase, cancer antigen (CA)125, and CA15-3, are known to be elevated in tuberculosis. CONCLUSIONS Patients with PV treated with ruxolitinib can develop active tuberculosis, including disseminated forms. When tumor markers are elevated and imaging reveals lesions suggestive of metastases, clinicians should include disseminated tuberculosis in the differential diagnosis and pursue histopathological and microbiological investigations to enable timely diagnosis and appropriate treatment.