The Usefulness of Point-of-Care Ultrasound in the Diagnosis of Erythema Nodosum: a Case Report

Abstract Point-of-care ultrasound is a useful tool in enhancing physical exam. It is a relatively new imaging technique for dermatological diagnosis, offering a rapid, non-invasive, and easily accessible evaluation in a wide variety of clinical scenarios. We present the case of a 41-year-old male with a history of dyslipidemia, Gilbert’s syndrome, and psoriasis. He presented with erythema, warmth, and pain in his lower limbs. Despite initial antibiotic treatments, he showed no improvement. A point-of-care ultrasound revealed hypoechoic thickening of the septa in the subcutaneous tissue and increased echogenicity of the lobules, indicating erythema nodosum. This led to further investigations, confirming a diagnosis of sarcoidosis. Initiation of corticosteroid therapy with prednisone resulted in an immediate clinical response and significant improvement. This case demonstrates the utility of point-of-care ultrasound as a complementary tool in dermatological inspection, offering a rapid, safe, low-cost, and readily available evaluation. It can be particularly helpful in the clinical suspicion of challenging-to-diagnose cases of panniculitis, confirming septal or lobular predominance, which is difficult to ascertain in a physical examination alone, and ruling out other causes such as cellulitis or venous thrombosis. Moreover, it can assist in guiding biopsies (targeting areas of greater involvement) and even monitoring the response to therapy. In this case, the combination of non-resolving clinical symptoms and the ultrasound findings prompted further diagnostic evaluation, leading to the correct diagnosis.