BACKGROUND. Idiopathic multicentric Castleman disease (iMCD) is a hematologic illness involving cytokine-induced lymphoproliferation, systemic inflammation, cytopenias, and life-threatening multi-organ dysfunction. The molecular underpinnings of interleukin-6 (IL-6) blockade-refractory patients remain unknown; no targeted therapies exist. In this study, we searched for therapeutic targets in IL-6 blockade-refractory iMCD patients with the thrombocytopenia, anasarca, fever/ elevated C-reactive protein, reticulin myelofibrosis, renal dysfunction, organomegaly (TAFRO) clinical subtype. METHODS. We analyzed tissues and blood samples from 3 IL-6 blockade-refractory iMCD-TAFRO patients. Cytokine panels, quantitative serum proteomics, flow cytometry of PBMCs, and pathway analyses were employed to identify novel therapeutic targets. To confirm elevated mTOR signaling, a candidate therapeutic target from the above assays, immunohistochemistry was performed for phosphorylated S6, a read-out of mTOR activation, in 3 iMCD lymph node tissue samples and controls. Proteomic, immunophenotypic, and clinical response assessments were performed to quantify the effects of administration of the mTOR inhibitor sirolimus. RESULTS. Studies of 3 IL-6 blockade-refractory iMCD cases revealed increased CD8 + T cell activation, VEGF-A, and PI3K/ Akt/mTOR pathway activity. Administration of sirolimus substantially attenuated CD8 + T cell activation and decreased VEGF-A levels. Sirolimus induced clinical benefit responses in all 3 patients with durable and ongoing remissions of 66, 19, and 19 months. CONCLUSION. This precision medicine approach identifies PI3K/Akt/mTOR signaling as the first pharmacologically targetable pathogenic process in IL-6 blockade-refractory iMCD. Prospective evaluation of sirolimus in treatment-refractory iMCD is planned (NCT03933904).

Interferon (IFN) therapy has been used for the treatment of common diseases such as hepatitis C, myeloproliferative disorders, autoimmune diseases and various types of cancer. Given the biological properties of interferon, it is not surprising that there are a larger number of side effects due to its use. Although rheumatoid arthritis (RA) is one of the most common autoimmune diseases found in clinical practice, it does not seem to be frequently related to IFN therapy. We report a 40-year-old female patient who, after high doses of IFN-alpha therapy for malignant melanoma, developed symmetrical polyarthritis, with pain and oedema in small and large joints, associated with prolonged morning stiffness. She had positive rheumatoid factor and DR4 HLA phenotype. She was treated with deflazacort (6 mg/day), chloroquine and NSAIDs, with a partial response. In conclusion, although the development of RA after IFN therapy is a rare event, IFN may work as a 'trigger' for such complication, leading to deregulation in the immune cascade in a person genetically predisposed.

Rationale:This is the report of the first case of TAFRO syndrome (Thrombocytopenia, Anasarca, myelofibrosis, Renal dysfunction, Organomegaly) in Latin America.Patient concerns:The patient was a 61-year-old white woman of Ashkenazi Jewish descent, who presented with a history of 8 days of nausea, vomiting, and fever; severe pitting edema in both legs, ascites, splenomegaly, and palpable axillary lymph nodes.Diagnoses:Abdominal computed tomography (CT) showed bilateral pleural effusion and retroperitoneal lymph node enlargement.Interventions:Anasarca and worsening of renal function led to admission to the intensive care unit (ICU) with multiple organ failure, requiring mechanical ventilation, vasopressor medications, and continuous renal replacement therapy (CRRT). Diagnosis of TAFRO syndrome was made on day 18 after admission, based on clinical findings and results of bone marrow and lymph node biopsies. She was treated with methylprednisolone, tocilizumab, and rituximab. One week after the first tocilizumab dose, she had dramatic improvements in respiratory and hemodynamic status, and was weaned from ventilator support and vasopressor medications.Outcomes:After 2 weeks of therapy, CRRT was switched to intermittent hemodialysis. On day 46, the patient was discharged from the ICU to the general ward, and 3 months after admission, she went home.Lessons:Provided the interleukin-6 measurement is available, this approach is suggested in cases of TAFRO syndrome, in order to customize the treatment.