[A toddler with a rare complication of scarlet fever].

Background: Haemolytic group A streptococci (GAS) are the most common bacterial cause of infection in the Netherlands. These bacteria can cause many different non-invasive infections, including scarlet fever.

Case description: A two-year-old girl presented with fever, tachycardia, exanthema and swelling in the neck. On suspicion of scarlet fever with neck phlegmon we treated her with antibiotics and supportive therapy. Blood and throat cultures revealed growth of haemolytic GAS. Lab tests revealed mild hyperthyroidism and neck ultrasound revealed an inhomogeneous appearance of the thyroid. We diagnosed her with 'infectious thyroiditis', a rare complication of infection with haemolytic GAS. A fistula from the pyriform sinus could not be demonstrated.

Conclusion: Although GAS infections are common, complications such as thyroiditis are rare. When a paediatric patient is diagnosed with infectious thyroiditis, a fistula from the pyriform sinus should be considered. Patients with such a congenital malformation have an increased risk of recurrent infectious thyroiditis and thyroid abscess formation.