Prurigo Nodularis at Ultra-High-Frequency Ultrasound

Figure 1. A 48-year-old female patient with chronic pruritus and persistent itching nodules. (A) B-mode ultrasound of one nodule shows hypoechoic dermal and hyperechoic epidermal thickening at 70 MHz; (B) color-Doppler ultrasound reveals hypervascularity of the lesion. Prurigo nodularis is a chronic inflammatory skin condition characterized by itchy hyperkeratotic crusted or eroded light-to-bright-red papules or nodules from a few millimeters to 2–3 cm in size, with hyperpigmented borders, usually bilaterally and symmetrically located in the dorsal part of the extremities, back and buttocks [1]. The median estimated prevalence of prurigo nodularis is 32.7 cases per 100,000 [2,3]. Dermatological examination is essential to try to identify associated diseases and underlying dermatoses that can be masked by prurigo nodularis. Dermoscopic white starburst pattern surrounding brown-reddish/brown-yellowish crusts, erosions and/or hyperkeratosis/scales can support the clinical diagnosis of prurigo nodularis [4]. Skin biopsy is necessary in prurigo nodularis of unclear origin. The aim of the treatment is to try to interrupt the itch–scratch cycle. First-line therapy for prurigo nodularis includes topical corticosteroids, antihistamines, calcineurin inhibitors and intralesional steroid injection. Second-line treatment is characterized by ultraviolet light therapy and/or systemic treatments such as immunosuppressants, gabapentinoids, antidepressants and mu-opioid receptor antagonists. Adult refractory patients can be treated with dupilumab, which is the first FDA- and EMA-approved drug for this disease [5,6]. To the best of our knowledge, no previous published articles have reported ultra-high-frequency ultrasound images about this disease, so this case can encourage prurigo nodularis studies in order to better assess ultrasound features and their usefulness in supporting clinical diagnosis and in distinguishing prurigo nodularis from other diseases, such as inconspicuous blister in pemphigoid nodularis or the common bullous pemphigoid in early stages, which would show anechoic subepidermal cystic structures with a hypoechoic subjacent upper dermis and no vascularization pattern [7,8].