Pôster:

The rheumatologic cutaneous manifestations closely resemble skin infections with indolent evolution. However, the diagnostic differentiation is important for a appropriate treatment. Erythema nodosum is an injury that is inserted in this context, can be associated with disease activity, but also tuberculosis. In the usual screening for the initiation of immunosuppression, a mandatory test is the tuberculin test, mainly when considering the Brazilian epidemiology. However, some patients may not be positive for this test even in the presence of tuberculosis infection. In this case, the differentiation of the two conditions becomes even more difficult. In the present report, we have a patient with cutaneous tuberculosis, who presented negative tuberculin test in the rituximab screening, worsening the lesion on the introduction of this medication.

Case report

Female, 47-year-old, with the diagnosis of overlapping syndrome of rheumatoid arthritis and dermatomyositis (polyarthritis, gotron papules, increased muscle injury markers, and electroneuromyography compatible with proximal myopathy) using prednisone, methotrexate, and azathioprine with regular control of the disease activity, started with panniculitis and erythema nodosum draining purulent secretion in the distal third of the left lower limb. It was considered a erythema nodosum hypothesis secondary to azathioprine, which was replaced by rituximab, aiming at better control of the disease and resolution of this cutaneous process. However, even after all necessary triage to iniciate rituximab, with the increase of immunosuppression, the lesion increased in extension and drainage of secretion. Patient was then referred to the infectology, initiated a investigation for mycobacteria, with the diagnostic, through the culture, of tuberculosis cutaneous lesion. So, it was iniciated the treatment with rifampicin, isoniazid, pyrazinamide and ethambutol for 6 months with complete resolution of the lesion.

Conclusion

Rheumatological manifestations and indolent skin infections, such as mycobacteria, show a great deal of clinical similarity, and should be considered as a differential diagnosis, even in patients with a negative tuberculin test.