[A serious adverse effect: sepsis due to carbimazole].

Thyonamides are widely used drugs to treat hyperthyroidism, because of their efficacy and security. However, although with less frequency, they can cause hepatic and haemathologic toxicity. Neutropenia produced for this kind of drugs, can be very serious, to such an extent it may jeopardize patient's life. If it appears, it is necessary to stop the antithyroid treatment and, if the patient have fever or agranulocytosis, start wide spectrum antibiotics and definitive treatment with radioiodine or surgery. A file case report of a 26-years-old woman with a thyrotoxicosis secondary to Graves' disease in treatment with carbimazole. She suffered a serious sepsis, as a consequence of the drug induced neutropenia.