Unraveling the mystery of fever of unknown origin: a remarkable journey towards the diagnosis of peripheral T-cell lymphoma-T follicular helper type: A rare case report.

INTRODUCTION: Fever of unknown origin (FUO) remains one of the most challenging clinical conditions. It demands an exhaustive diagnostic approach, considering its varied etiologies spanning infectious, autoimmune, inflammatory, and malignant causes. PATIENT CONCERNS: This report shows the journey of diagnosing a 28-year-old male who presented with persistent fever and lower-extremity weakness over 9 months. Despite seeking care at multiple hospitals, a definitive diagnosis remained elusive. DIAGNOSIS: The patient underwent a series of evaluations in various specialties, including gastroenterology, infectious diseases, rheumatology, hematology, and cardiology. Multiple tests and treatments were administered, including antiviral therapy for hepatitis B and antibiotics for suspected infections. INTERVENTIONS: After an initial misdiagnosis and unsuccessful treatments, a positron emission tomography-computed tomography scan and lymph node biopsy ultimately led to the diagnosis of peripheral T-cell lymphoma-T follicular helper type (PTCL-TFH) lymphoma. The patient was referred to the hematology clinic and initiated on CHOEP (cyclophosphamide, vincristine, etoposide, and prednisone) chemotherapy. OUTCOMES: The patient showed a positive response to CHOEP therapy, as indicated by a posttreatment positron emission tomography-computed tomography scan. He reported a significant improvement in his quality of life. Additional rounds of the same regimen were planned to further manage the lymphoma. CONCLUSION: This case emphasizes the importance of a comprehensive and persistent diagnostic approach in managing FUO. Initially, the focus on infectious causes led to extensive treatments, but the disease's progression and complications shifted attention to other specialties. The eventual diagnosis of PTCL-TFH lymphoma highlights the significance of advanced imaging techniques and multidisciplinary collaboration in uncovering elusive diagnoses. Thorough surveillance, timely reassessments, and repeated testing can uncover definitive changes critical for diagnosis. PTCL-TFH lymphoma, although rare, should be considered in the differential diagnosis of FUO, especially when initial evaluations are inconclusive.

Renal cell carcinoma presented with a rare case of icteric Stauffer syndrome: A case report.

BACKGROUND: Paraneoplastic syndromes remain poorly understood and manifest as multifaceted clinical symptoms, making their diagnosis difficult. Cholestasis can be observed in various malignancies. In rare cases, it can be a paraneoplastic manifestation, most often associated with renal cell carcinoma and other urogenital tumors, as well as with bronchial carcinoma. The classical form of Stauffer syndrome presents with a reversible anicteric increase of cholestatic liver function tests, thrombocytosis, coagulation impairment, and hepatosplenomegaly, without any proven hepatobiliary obstruction or metastases. CASE SUMMARY: We report a patient who presented with elevated liver enzymes, cholestatic jaundice, weight loss and pruritus, in whom renal cell carcinoma was incidentally found during hospitalization. Clinical, laboratory, and imaging tests excluded primary hepatic cause or metastatic disease. Jaundice and laboratory abnormalities reversed completely a few months after nephrectomy. This case is an example of the many sides of renal cell carcinoma, and it focuses the clinicians' attention on the differential diagnosis of cholestasis, including Stauffer syndrome and its variant. Thus, the correct diagnosis can be straightforward and the associated malignancy can be treated promptly. All cases should be followed up with a multidisciplinary team. Interleukin (IL)-6 is proposed to contribute to the pathophysiology of the condition. The probable mechanism is proinflammatory activity by the IL-6 cytokine, causing elevation of C-reactive protein and haptoglobin and inhibition of hepatobiliary transporter gene expression, impairing biliary outflow. CONCLUSION: Despite being rare, Stauffer syndrome is a potentially reversible paraneoplastic condition, when the primary cause is treatable. This syndrome should be considered by clinicians because of the remediable liver disturbance, after successful treatment of the underlying malignancy.