A case of Poncet disease diagnosed with interferon-γ-release assays

In this Case Study, the authors describe a patient with Poncet disease, a rare form of polyarthritis associated with tuberculosis infection. They discuss their application of interferon-γ-release assays and PCR specific for DNA of theMycobacteria tuberculosis complex to make the diagnosis, despite a negative M. tuberculosisculture. Background. A 55-year-old, HLA-B27-positive Finnish woman presented with migratory, sterile polyarthritis. Investigations. Physical examination, chest radiography, serologic testing, microscopy, M. tuberculosis-specific interferon γ enzyme-linked immunospot (ELISPOT) assay, smear and culture of synovial fluid for acid-fast bacilli, and PCR. Diagnosis. The patient's assayed blood and synovial fluid lymphocytes were reactive, and the numbers of M. tuberculosis-specific T cells, as determined by ELISPOT, were twofold to sixfold higher in synovial fluid than in blood. Cultures for acid-fast bacilli remained negative, while PCR specific for DNA of the M. tuberculosis complex was positive in synovial fluid cells. These results suggested that the patient had either active or latent M. tuberculosis infection. This finding, coupled with the presence of polyarthritis, led to a diagnosis of Poncet disease. Management. Standard antituberculous therapy consisting of isoniazid, rifampicin and pyrazinamide was given for 2 months, followed by isoniazid and rifampicin for 4 months. Inflamed joints were treated with methylprednisolone injections. The polyarthritis resolved within 4 months of initiating antituberculous therapy.