Radiotherapy-induced hyperthyroidism in a cystinotic kidney transplant patient with Hodgkin lymphoma

Hypothyroidism is a well-known complication of cystinosis. PTLD incidence in pediatric renal transplant population ranges between 1 and 4.5%. We describe the case of a young cystinotic patient who developed hyperthyroidism after radiotherapy for Hodgkin lymphoma. He is a 23-yr-old male who was diagnosed with cystinosis at the age of two. He developed renal failure and other extrarenal complications but never presented hypothyroidism. At the age of 12, he received a successful kidney transplant from a cadaveric donor. Two yr later, EBV-positive Hodgkin lymphoma was diagnosed and chemotherapy and radiotherapy were administered. He achieved remission. Eight yr later, autoimmune hyperthyroidism secondary to previous radiation was detected, and he slowly became symptomatic. Clinical symptoms and laboratory data spontaneously normalized. This is the first case of a cystinotic patient developing hyperthyroidism. Thyroid disorders, especially hypothyroidism, have been reported in association with neck irradiation. Hypothyroidism would have been considered to be a late complication of cystinosis and not a consequence of radiotherapy. Thyroid hormones, clinical examination, and history evaluation for thyroid dysfunction should be periodically monitored after neck radiotherapy. The thyroid should always be excluded from the irradiation fields. Multidisciplinary interaction in difficult cases should be encouraged.