Encephalopathy and sinustachycardia in childhood--a possible differential diagnosis.

We report on a 7-year-old girl with generalized seizures, somnolence, fever, and respiratory distress. The increase of sinus tachycardia with good hydration, sufficient analgesia, and hyperthermia in our patient led to the determination of thyroid hormones, and therefore finally to the diagnosis of a thyrotoxic crisis in Graves' disease. Thyrotoxic crisis is a very rare but severe disease with an incidence of 0.1/100,000-3/100,000 among children. Important differential diagnoses of hyperthyroidism are Hashimoto thyroiditis, paraneoplastic thyroid-stimulating hormone production, thyroid autonomy, as well as central hyperthyroidism. Although symptoms disappear by thyrostatic therapy (thiamazole, carbimazole, dexamethasone), a euthyroid status could only be achieved by thyroidectomy. Thyrotoxic crisis should be considered a differential diagnosis in case of resistant unexplained sinus tachycardia, seizures, and encephalopathy. Immediate and adequate therapy contributes significantly to a reduction in the high morbidity and mortality rates. A combination of several treatment approaches for hyperthyroidism can lead to a successful outcome.