Clinical presentation: a 33-year old woman referred for evaluation of neck complaints. Her left thyroid became painful for 3 weeks. The GP administered non-steroid anti-inflammatory drug but the pain did not resolve after a week.

Palpation: both thyroids were hard and the left was also painful.

Functional state: hyperthyroidism with TSH-level 0.15 mIU/L, FT4 28.2 pM/L, We 15 mm/H, CRP 2.1 mg/L (normal value: 0-4.8).

Ultrasonography: the right thyroid was echonormal with a hypoechogenic lesion in the dorsal part. The left thyroid contained several hypoechogenic areas with blurred borders. The vascularization was average.

Cytological and final diagnosis: subacute, granulomatous de Quervain's thyroiditis.

Suggestion: steroid therapy.

3 months later the patient had no complaints. The sonographic pattern has normalized except for small hypoechogenic areas in both lobes. We performed antibody determination which resulted in a normal level: aTPO 7 U/mL, ahTg 0 U/mL.

Comment. This is a very unusual situation that sedimentation rate and CRP are normal in an active phase of de Quervain's thyroiditis. We met only 3 patients with such a condition among more than 600. In such cases, Hashimoto's thyroiditis has to be considered, and in spite of normal antibody levels, it cannot be excluded except for an absolutely unequivocal cytological pattern. It requires the presence of multinucleated giant cells composed of epitheloid cells.