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An 8-year-old boy with a round scaly plaque
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An 8-year-old male presented to pediatric dermatology for evaluation of a round dry patch on the back of his left thigh. The lesion has been present for 2 years and initially started as a quarter-sized hypopigmented patch that became larger, more erythematous and scaly with time. The lesion is asymptomatic, with no pain or pruritus in the area. Several fungal cultures were done in the past but were all negative, according to the treating physician. He even completed a 4-week trial of topical antifungal therapy without improvement. The patient is otherwise healthy and does not have a history of eczema or dry skin.
Shehla Admani
Andrew C.
Krakowski
On physical exam, the patient is noted to have an ovoid, follicular, hairless, pinkish-orange, scaly plaque with a rim of hypopigmentation on his left posterior thigh. The rest of his skin exam is within normal limits. Potassium hydroxide (KOH) preparation in clinic to examine for fungus reveals no fungal elements.
What is the next best step in this patient’s treatment?
A. Repeat fungal culture
B. Biopsy
C. Topical corticosteroids
D. Bacterial culture
E. Patch testing
F. Moisturizers and sunscreen
Can you spot the rash?
Diagnosis: Mycosis Fungoides
The most common round scaling plaques that are seen in pediatric patients are tinea corporis and nummular eczema. The clinical features in this patient’s case that were of particular concern were the 2-year duration, history of negative fungal cultures, no response to antifungal therapy, no history of eczema, and absence of any additional lesions in stereotypical “eczema” distribution. To further aid in the child’s diagnosis, a 4-mm punch biopsy was performed, which showed mycosis fungoides.
Mycosis fungoides is the most common form of cutaneous T-cell lymphoma. It is rare in children, with juvenile mycosis fungoides consisting of less than 5% of all mycosis fungoides cases. As a result, the clinical suspicion for mycosis fungoides in the pediatric population is generally low. The two most common types of mycosis fungoides seen in children are hypopigmented and folliculotropic (consisting of spiny follicular papules), or a combination of the two.
Hypopigmented mycosis fungoides can often be difficult to distinguish from post-inflammatory hypopigmentation. However, the presence of a persistent hypopigmented patch in a sun-protected area should lead to the consideration of mycosis fungoides. In contrast to adults, in which the head and neck are the most common areas of involvement with folliculotropic mycosis fungoides, children often have involvement of the trunk and extremities including sun-exposed areas.
Juvenile mycosis fungoides cases tend to present with early-stage disease and have a better prognosis than those in adults. Treatment options vary based on type of mycosis fungoides and number and distribution of lesions; these include phototherapy, chemophototherapy, topical corticosteroids, topical nitrogen mustard and electron beam therapy. After a lengthy discussion with the family, this patient opted for treatment with high-potency topical steroids and a 3-month follow-up visit.
Posterior thigh with round, pink/orange, hairless scaling plaque with follicular prominence and rim of hypopigmentation.
Source: Krakowski AC
In patients with a history of an isolated, well-defined, eczematous appearing plaque, the differential diagnosis should include allergic contact dermatitis. However, allergic contact dermatitis is typically pruritic, and the patient may have a history of repeated exposures to the offending agent. Likewise, there is often a “bilateral and symmetric” aspect to the presentation. These features were not present in this patient; however, if they were, patch testing should be considered because it is the gold standard for the diagnosis of allergic contact dermatitis.
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Andrew C. Krakowski, MD, is an attending physician at Rady Children’s Hospital, San Diego.
Disclosure: Admani and Krakowski report no relevant financial disclosures.