Levothyroxine sodium (Thyradin S®) (L-T4) is one of the most useful drugs for replacement therapy in primary hypothyroidism. There have been few side effects reported. We report a rare case with chronic thyroiditis accompanied by drug eruption induced by L-T4.
A 68-year-old man consulted our hospital for nasal bleeding and anemia. He was diagnosed as allergic rhinitis and hypothyroidism due to chronic thyroiditis, and the replacement with L-T4 was started. On the eleven months after the start of L-T4 treatment, erythematous eruption with severe itching appeared on his chest, back, upper and lower extremities. In spite of stopping all other drugs except L-T4, the eruption did not disappear. When the L-T4 was discontinued, the eruption disappeared within 3 weeks. The scratch patch test revealed the hypersensitivity for L-T4 in this patient. The challenge test with L-T4 resulted in itching but not eruption after 72 hours. The skin biopsy revealed the superficial perivasculitis accompanied by infiltration of eosinophils and lymphocytes. These findings suggest that the drug eruption was induced not only by L-T4 accumulation, but partly attributed to allergic reaction for L-T4.
