Dermatology: Practical and Conceptual Image Letter | Dermatol Pract Concept. 2023;13(2):e2023102 1 “Dot in a Circle”: a Useful Ultrasound Finding for a Rapid Diagnosis of Mycetoma Vincenzo Maione1, Chiara Cozzi1, Marina Venturini1, Angela Napolitano2, Piergiacomo Calzavara-Pinton1 1 Department of Dermatology, Spedali Civili, University of Brescia, Brescia, Italy 2 Department of Neuroradiology, ASST Papa Giovanni XXIII, Bergamo, Italy Citation: Maione V, Cozzi C, Venturini M, Napolitano A, Calzavara-Pinton P. “Dot in a Circle”: an Useful Ultrasound Finding for a Rapid Diagnosis of Mycetoma. Dermatol Pract Concept. 2023;13(2):e2023102. DOI: https://doi.org/10.5826/dpc.1302a102 Accepted: September 25, 2022; Published: April 2023 Copyright: ©2023 Maione et al. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original authors and source are credited. Funding: None. Competing Interests: None. Authorship: All authors have contributed significantly to this publication. Corresponding Author: Vincenzo Maione, Department of Dermatology, Spedali Civili, University of Brescia, Brescia, Italy. Tel +39 030 3995301 Fax +39 0303995015 E-mail: maionevincenzo@gmail.com Case Presentation A 65-year-old man from Senegal presented to our Clinic with a 15-year history of a nodular enlarging mass on his left foot. Clinical examination revealed a large painless lesion with crusting and purulent discharge (Figure 1A). The lesion gradually enlarged, leading to deformity and walking impairment. Before biopsy, we performed an ul- trasonography which showed hypoechoic areas containing hyperechoic foci, a typical “Dot in a circle” sign (Figure 1B). A  subsequent MRI of the foot confirmed ultrasound find- ings, revealing well-defined hyperintense lesions with periph- eral hypointense rim and central hypointensities, confirming our hypothesis of mycetoma. In addition an underlying osteomyelitis was diagnosed (Figure 1C). After a first nega- tive culture, we collected new skin samples under ultrasound guidance which resulted positive for Staphylococcus caprae and Bacillus pumilus. The patient was treated with ampicillin, after a surgical debulking. Teaching Point Madura foot or mycetoma is endemic disease in tropical regions and takes its name from the Indian city of Madurai, where it was described for the first time. Its clinical pre- sentation, typified by sinuses, subcutaneous nodules and 2 Image Letter | Dermatol Pract Concept. 2023;13(2):e2023102 purulent discharge, is due to a granulomatous reaction to fungal hyphae (Eumycetoma) or bacteria (Actinomycetoma) aggregates - the “grains” [1]. These pathological findings can be assessed with different diagnostic tools. For instance, Der- moscopy displays multiple papules, disappearance of skin furrows and fistulous tracts extruding grains. In additional other dermoscopic features include blood spots, erosions, orange-yellowish structureless areas [2]. Ultrasonography seem to be more specific showing a peculiar aspect called “dot in a circle” [3], which correlates directly with the presence of grains. Microbiological culture from skin biopsy is necessary to confirm diagnosis but often results difficult, delaying treat- ment. Ultrasound is rapid and low-cost technique – available also in Dermatology Clinics- which assists early diagnosis and helps appropriate specimen collection for culture, avoiding multiple surgical interventions. References 1. Verma P, Jha A. Mycetoma: reviewing a neglected disease. Clin Exp Dermatol. 2019;44(2):123-129. DOI: 10.1111/ced.13642. PMID: 29808607. 2. Errichetti E, Ankad B, Chatterjee M, Calzavara-Pinton P, Maione V, Chauhan P. Mycosis. In: Dermoscopy in General Dermatology for skin of Color. Errichetti E, Lallas A (Eds) 1th ed. 2022:132-133. DOI: 10.1201/9780367816483. 3. Petscavage JM, Richardson ML. Madura foot masquerading as a hemangioma. Radiol Case Rep. 2015;5(1):355. DOI: 10.2484 /rcr.v5i1.355. PMID: 27307847. PMCID: PMC4898212. Figure 1. (A) Painless mass of the plantar surface of the left foot with a purulent discharge. (B) Ultrasound (14-20 MHz Us Transducer – MylabTMOne, Esaote) evidenced a hypoechoic area containing hyperechoic foci, due to granulomatous reaction to bacteria grains. (C) Sagittal T2 weighted STIR MRI confirms the presence of “dots in a circle sign” associated to osteomyelitis.