[Paniculitis as manifestation of prolonged febrile syndrome: Case report].

Fever of unknown origin (FUO) is defined as fever over 7 to 10 days without a diagnosis despite a complete initial study. The most frequent causes are infections, autoimmune and tumors. Even though most cases are self-limited there is a minority that has an underlying etiology with an ominous forecast, encouraging a systematized study. OBJECTIVE To report a rare case of a boy who presented fever of unknown origin associated to panniculitis and was diagnosed of subcutaneous panniculitis-like-T cell lymphoma and to emphasis the importance of a sequential study of FUO, in order to reach a diagnosis in patients who need a timely intervention. CLINICAL CASE A ten year old boy, previously healthy, presented subcutaneous nodular lesions of 2 month of evolution, located in abdominal region and extremities, given few symptoms, associated with prolonged fever. He was hospitalized for proper study, in first instance infectious and immune causes were discarded and through lesions biopsy the diagnose of subcutaneous panniculitis-like-T cell lymphoma was reached. CONCLUSION When FUO is diagnosed, most prevalent causes must be discarded. Then, differential diagnosis, such as immune and neoplasic etiologies, have to be considered. If FUO is associated to elemental nodular lesions, biopsy must be indicated early, in order to find potential malignant cases, avoiding therapeutic delay.