Background: Fever can be the presenting symptom of metastatic breast carcinoma, but the combination of fever, polyarthritis, and an erythematous rash as a paraneoplastic syndrome in breast carcinoma is very rare.
Methods: The clinical course of a 49-year-old female with a history of ductal breast carcinoma who presented with fever of unknown origin, polyarthritis, and an erythematous rash is described. Moreover, cytokine measurements were performed.
Results: Initially, despite extensive evaluation, a diagnosis could not be made. Six weeks after the onset of symptoms, a right axillary lymph node became palpable and the diagnosis of relapsing breast carcinoma was made. Chemotherapy led to defervescence and disappearance of the symptoms. Elevated interleukin-6 and interleukin-1 receptor antagonist concentrations were found.
Conclusion: To the authors' knowledge, the severe paraneoplastic signs encountered in this patient have not been described in breast carcinoma. The presentation is even more remarkable in view of the relatively small visible tumor mass.