Boy presents with ringlike lesion on his arm
What’s your diagnosis?
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A 10-year-old boy comes to your clinic with a chronic, enlarging lesion on his right arm. It began as an erythematous bump that slowly enlarged in a ringlike fashion, with a reddish color to the ring. There is minimal erythema but flaking skin in the center of the lesion. He notes that there has been mild pruritus but no pain. He is otherwise healthy, and his immunizations are up to date. Specifically, he denies any history of skin problems. The family history is unremarkable, with no other family members with any skin problems.
On examination, you verify the lesion as described, with an erythematous, somewhat raised ring and some small papules, and a central clearing and desquamation (Figure 1). He has no fever or other significant findings.
What’s your diagnosis?
A. Granuloma annulare
B. Nummular eczema
C. Tinea corporis
D. Urticaria pigmentosa
Answer and discussion:
This is common tinea corporis, caused by one of the dermatophytes — choice C. With experience, most providers can diagnose the problem by the characteristic visual appearance. However, it might be prudent to document the cause if empiric treatment does not work. This can be done using the DTM (dermatophyte test medium) culture system. In this case, the organism was Trichophyton mentagrophytes. Of the numerous species, the most common cause is T. rubrum. Others include Microsporum species. Topical antifungal agents, such as clotrimazole, ketoconazole, miconazole, etc. are usually successful, especially for single lesions. Treatment of multiple or resistant lesions can be with oral griseofulvin, itraconazole or terbinafine, and others (see the 2021 Red Book for details).
Granuloma annulare also starts as an inflammatory papule, which expands into a circular plaque with central clearing, usually on the extremities. The ring edge is often studded with small erythematous papules, and the central skin usually appears clear. The cause is unknown, but various causes have been proposed, such as minor injuries and drug reactions, and some have associated its occurrence with various endocrinopathies. Most do not require treatment, but for those that do, topical steroids, cryotherapy or immune modulators such as topical tacrolimus may be tried. These patients are probably best managed by a dermatologist. To see an excellent example of this lesion, I would recommend going to DermNet.org and search “granuloma annulare.” This is an excellent dermatology site with thousands of high-quality images that can be viewed for free, with excellent descriptions.
Nummular eczema, also known as discoid eczema, is a form of dermatitis that occurs in an annular configuration and likely a form of atopic dermatitis. It is more common in older adults but can be seen at any age. Most experts divide nummular eczema into a dry form and a wet or exudative form (Figures 2 and 3, respectively).
Symptoms are usually minimal, and treatment is the same as for common atopic dermatitis: topical steroid cream and emollients. Cases that do not respond well should probably be referred to a dermatologist.
Urticaria pigmentosa is an uncommon form of mastocytosis, a condition where mast cells are concentrated in certain tissues, including the skin and/or internal organs (systemic mastocytosis). Skin lesions may be solitary or numerous (Figure 4).
They may appear similar to other annular lesions but not raised or desquamating.
In the primary care office, one may test for the Darier sign by rubbing a lesion with a tongue blade or similar object (Figures 5 and 6) to see if there is a flair of erythema as evidence of degranulation of underlying mast cells (Figure 7).
With that, the patient can be referred to dermatology for further evaluation. Systemic mastocytosis may manifest as allergic reactions, and diagnosis can be confirmed by biopsy of involved tissue.
Columnist comments
Hopefully, the fall is arriving without too much fanfare, but just in case, be sure to get your influenza immunization and the new COVID-19 vaccine booster, as well as those for whom you love and your patients.
Lastly, election time is upon us, and while I have on occasion financially supported candidates without regard for their party affiliation from time to time, I consider myself neutral or apolitical. However, I never miss a chance to vote. I am not against beating your chest and shouting your opinion from the highest mountain, but it does no good if you don’t get into the voting booth and mark your choices. Perhaps I’ll see you there.
For more information:
Brien is a member of the Healio Pediatrics Peer Perspective Board and an adjunct professor of pediatric infectious diseases at McLane Children's Hospital, Baylor Scott & White Health, in Temple, Texas. He can be reached at jhbrien@aol.com.
Reference:
- American Academy of Pediatrics. Committee on Infectious Diseases. Red Book. Report of the Committee on Infectious Diseases. Academy of Pediatrics; 2021. https://redbook.solutions.aap.org/redbook.aspx. Accessed Oct. 24, 2022.