Autoimmune Thyroid Disease in Patients with Philadelphia-Negative Chronic Myeloproliferative Neoplasms Treated with Interferon-Alpha

Objectives: Interferon-alpha (IFN-α) is increasingly being used in the treatment of the Philadelphia-negative chronic myeloproliferative neoplasms (MPNs). However, some 20% of patients discontinue treatment because of side effects, including thyroid dysfunction. Methods: This retrospective study reports patients with MPNs who developed autoimmune thyroid disease (AITD) during treatment with IFN-α, representing 5.0% of the cohort (n=160). Results: Eight patients (seven women) developed AITD with positive thyroid peroxidase antibodies. Seven patients had polycythemia vera (PV) and one essential trombocythemia (ET). The patients were younger than average and developed AITD 5-86 months after initiation of IFN-α, six within 15 months. In two patients, thyroid-stimulating hormone normalized after decreasing dosage of IFN-α and discontinuation of treatment, respectively. Conclusion: This report underscores the importance of monitoring thyroid function before and during therapy, since the side effects of IFN-α may mimic thyroid disease. Although discontinuation of IFN-α therapy should be considered, it is possible to continue treatment.