3-year-old boy presents with annular rash on leg

A 3-year-old boy presented to the dermatology clinic with a rash on his right leg. The rash started 3 months earlier as a single lesion, then a second lesion developed a few weeks later.

The rash was composed of two round flesh-colored plaques with central clearing and raised borders but without scaling (Figures 1 and 2). It was neither itchy nor painful and did not appear to bother the patient. No one else at home had any similar lesions. Treatment with clotrimazole 1% cream twice daily for 4 weeks did not clear the rash.

Can you spot the rash?

A. Tinea corporis
B. Granuloma annulare
C. Erythema annulare centrifugum
D. Nummular eczema
E. Psoriasis

Case discussion

The correct answer is B, granuloma annulare (GA), a common benign inflammatory dermatosis characterized by granulomatous inflammation involving the dermis or subcutaneous fat. Lesions can be solitary or multiple and classically present as annular (ring-shaped) plaques with central clearing. The borders of the lesion are composed of smaller papules that are flesh-toned or pink-erythematous in color. If there is involvement of the subcutis, deeper nodules may be the more prominent clinical finding. GA is typically asymptomatic, although occasionally it may be pruritic. GA usually presents in young children but can be seen at any age. The cause is unknown.

Several clinical variants of GA exist. Localized disease is the most common presentation (75% of cases), with lesions limited to the extremities, especially on the dorsal hands and/or feet. A generalized variant presents with a more widespread distribution that also can involve the trunk. This variant is more common in adults and may be associated with underlying diabetes mellitus, dyslipidemia, thyroid disease or malignancy, and therefore, additional workup should be considered in these patients. Subcutaneous GA presents as firm nodules often on the lower extremities and is seen most frequently in children. Finally, perforating GA presents as papules with central umbilication or crusting due to extrusion of collagen. GA can usually be diagnosed clinically, especially in localized disease. A skin biopsy can confirm the diagnosis if needed and is usually necessary to diagnose the subcutaneous variant.

The differential diagnosis of an annular rash also includes infectious etiologies like tinea corporis (ringworm) and inflammatory etiologies like erythema annulare centrifugum. However, an important clinical distinction between GA and these entities is that GA is not scaly. GA is commonly misdiagnosed as tinea corporis and referred to dermatology for failing treatment with antifungal therapy. Erythema annulare centrifugum is an inflammatory dermatosis uncommon in children that usually presents as annular plaques with a ring of scale that trails behind the advancing edge of the lesion. It is thought to be due to a hypersensitivity reaction to an infection, drug, systemic disease, or malignancy, although an etiologic agent is often not identified. Nummular eczema and psoriasis can present as round plaques, but they typically are scaly and do not usually present with central clearing.

Overall, GA is a benign entity that resolves spontaneously within 2 years and does not require treatment for localized disease. If treatment is desired or if lesions are symptomatic, topical steroids may be effective. In older patients, intralesional steroids can also be offered for localized disease. It is important to counsel patients and their families that atrophy is a potential side effect of topical or intralesional steroids. Reassurance is also important when counseling families on the benign nature of this disease.

References

Paller A, Mancini AJ, eds. Hurwitz Clinical Pediatric Dermatology: A Textbook of Skin Disorders of Childhood and Adolescence. 5th ed. Edinburgh: Elsevier; 2016: 557-572.

Perafán‐Riveros C, et al. Pediatr Dermatol. 2002;doi:10.1046/j.1525-1470.2002.00200.x.

Tabanliolu D, et al. Pediatr Dermatol. 2009;doi:10.1111/j.1525-1470.2008.00803.x.

For more information:

Khurana is an attending physician at The Children’s Hospital of Philadelphia. She can be reached at khuranam@email.chop.edu.