I saw the "thyroid inferno" sign: A fiery Doppler signature of Graves' disease.

Color Doppler ultrasonography was first used in 1988 by Ralls et al. to evaluate blood flow to the thyroid gland in patients with Graves' disease [1]. The "thyroid inferno" is the imaging demonstration of markedly increased vascularity and arteriovenous shunting seen with Graves' Disease (Fig. 2 and 1B) b[1]. This pattern consists of multiple small pulsatile areas of intrathyroidal flow seen diffusely throughout the gland in both systole and diastole. This hypervascularization reflects the hemodynamic changes of hyperfunctioning thyroid and/or an ongoing inflammatory process and is similar in color Doppler appearance to the homonymous "Inferno sign" in epididymo- orchitis [2]. Thyroid inferno is an imaging sign, which should not be mistaken with thyroid storm (hyperthyroid crisis) which is a clinical presentation of severe thyrotoxicosis. Though the clinical picture varies, the greyscale ultrasound picture of Graves' disease may be indistinguishable from Hashimoto's thyroiditis and de Quervain's thyroiditis as they often present with heterogenous and hypoechoic, diffuse glandular enlargement (Fig. 1A) [3]. Color Doppler has shown to help distinguish untreated Graves' disease from Hashimoto's thyroiditis, as marked hypervascularity is more characteristic of untreated Graves' disease [4]. It is notable that occasionally there might be hypervascularity in early Hashimoto thyroiditis. Additionally, in subacute thyroiditis, any degree of vascularization is possible [5]. Despite these overlaps, hypervascularization remains an important sonographic feature of Graves' disease [4]. Furthermore, in Graves' disease patients currently on treatment, increased blood flow detected prior to treatment cessation has shown to be a predictor of disease recurrence should treatment be stopped.