Peer Reviewed

Photo Quiz

What Is This Rash on an Older Man’s Groin?


    Kathleen E. Kramer, MD1 • Angela M. Crotty, MD2

    1Aviation Medicine, Naval Branch Health Clinic Coronado, Naval Medical Center San Diego, Coronado, California
    2Department of Dermatology, Naval Medical Center San Diego, San Diego, California

    Kramer KE, Crotty AM. What is this rash on an older man’s groin? Consultant. 2022;62(10):e13-e15. doi:10.25270/con.2021.11.00002

    Received May 6, 2021. Accepted May 17, 2021. Published online November 10, 2021.

    The authors report no relevant financial relationships.

    The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, the Department of Defense, or the US Government.

    Kathleen E. Kramer, MD, Naval Branch Health Clinic Coronado, 601 McCain Boulevard, Coronado, CA 92135 (


    A 62-year-old man presented to our dermatology clinic with several-year history of a groin rash. It had waxed and waned over the years, with occasional episodes of associated pruritis elicited by periods of increased sweating.

    History. He was otherwise healthy with no significant medical history. He reported showering early that morning and had been showering roughly twice daily in an effort to ensure his groin area was clean.

    The rash had been treated previously with topical nystatin powder, oral terbinafine, oral itraconazole, topical econazole, and tacrolimus prescribed by his primary care physician. The patient reported transient improvement in the appearance of the rash with application of antifungal creams and over-the-counter moisturizers, but it did not clear completely with those modalities.

    Physical examination. The patient had a skin phototype 2, was well-nourished, and was not in acute distress. Upon gross examination, the patient displayed uniformly pink to brown plaques with clearly demarcated borders and minimal overlying scale, extending from the bilateral inguinal creases and involving lateral aspects of the scrotum and proximal inner thighs bilaterally (Figure 1). When examined with a Wood’s lamp, the area showed coral-red fluorescence (Figure 2).

    Figure 1. Plaques were noted bilaterally on the patient’s groin.
    Figure 1. Plaques were noted bilaterally on the patient’s groin.

    Figure 2. The patient’s groin lesions fluoresced when examined via Wood’s lamp.
    Figure 2. The patient’s groin lesions fluoresced when examined via Wood’s lamp.



    Answer and discussion on next page.


1. Garcia-Souto F. Visual dermatology: erythrasma fluorescence under Wood's lamp. J Cutan Med Surg. 2020;24(1):94.

2. Bacterial infections. In: Habif TP, ed. Clinical Dermatology: A Color Guide to Diagnosis and Therapy. 6th ed. Elsevier; 2016;329-374.

3. Forouzan P, Cohen PR. Erythrasma revisited: diagnosis, differential diagnoses, and comprehensive review of treatment. Cureus. 2020;12(9):e10733.

4. Edwards SK. Genital rash (including warts and infestations). Medicine. 2018;46(6):325-330.

5. Janeczek M, Kozel Z, Bhasin R, Tao J, Eilers D, Swan J. High prevalence of erythrasma in patients with inverse psoriasis: a cross-sectional study. J Clin Aesthet Dermatol. 2020;13(3):12-14.

6. Makrantonaki E, Jiang D, Hossini AM, et al. Diabetes mellitus and the skin. Rev Endocr Metab Disord. 2016;17(3):269-282.

7. Moini J. Skin problems. In: Moini J, Ahangari R, Miller C, Samsam M, eds. Global Health Complications of Obesity. Elsevier; 2020:289-314.

8. Zhao Z, Ma L. Skin and soft tissue infections: a clinical overview. In: Tang YW, Sussman M, Liu D, Poxton I, Schwartzman J, eds. Molecular Medical Microbiology. 2nd ed. Academic Press; 2015:825-835.

9. Chodkiewicz HM, Cohen PR. Erythrasma: successful treatment after single-dose clarithromycin. Int J Dermatol. 2013;52(4):516-518.