DermaDiagnosis

Making the Rounds to Diagnosis

Publish date: May 11, 2021
Author(s):
Joe R. Monroe, MPAS, PA
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Lesion

A 60-year-old woman is feeling fine—no fever, arthralgia, or malaise—but the sudden appearance of lesions on her extremities unsettles her to the point that she can think of little else. Visits to her primary care provider, the emergency department, several urgent care clinics, and a naturopath yield a consistent diagnosis: ringworm. Yet none of the topical or oral antifungal medications she is prescribed make the slightest difference. Thus, she finally agrees to consult a dermatologist.

The patient reports decent health, although she was a heavy smoker for years before quitting 2 years ago. She recently tested negative for diabetes.

History taking reveals no sources from which she could have acquired a fungal infection. No one else at home is similarly affected.

About 10 lesions, mostly located on the patient’s extremities, are examined. All are very similar in appearance: round, brownish-red intradermal plaques with no epidermal component (eg, scale, broken skin). The lesions vary from 6 mm to 4 cm in diameter. The centers of most lesions are slightly concave, with well-defined raised margins. On palpation, there is neither increased warmth nor tenderness. No nodes can be palpated in the groin, axillae, or epitrochlear locations.

A deep punch biopsy is performed on a thigh lesion, with the specimen submitted for pathologic examination.

The most likely diagnostic explanation is

Sarcoidosis

Cutaneous T-cell lymphoma

Lupus profundus

Granuloma annulare

ANSWER

The correct answer is granuloma annulare (GA; choice “d”).

DISCUSSION

The biopsy showed rings of dermal epithelioid histiocytes surrounding a core of central mucin, configured in rows (the latter conferring the diagnostic term “palisaded” granulomas). Both the pathology results and the morphology of the lesions—color, shape, etc—were classic for GA. What was somewhat unusual about this case was the size and number of lesions, which are typically fewer and smaller with GA.

GA is seldom much of a problem and has no connection to serious disease. But it can, as this case illustrates, mimic some rather worrisome conditions. Had this been sarcoidosis (choice “a”), there would be no central “delling” (concavity), and the biopsy would have shown necrotic (caseating) nonpalisading granulomas.

Cutaneous T-cell lymphoma (CTCL; choice “b”) can manifest with plaques, but there wouldn’t be any delling and the shapes would not be so consistently round. CTCL will eventually give rise to palpable adenopathy.

Lupus profundus (choice “c”) also manifests with deep plaques, without delling. It is a truly rare variant of lupus, which would have been detected on biopsy.

Concern about these differential items is what drove the decision to perform full-thickness punch biopsies as opposed to taking a simple shave sample.

TREATMENT

The most common treatment for GA is intralesional steroid injection (eg, 10 mg/cc triamcinolone) of large lesions. Oral medications such as methotrexate or pentoxifylline have been used with some success. Often, the condition is self-limiting.

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Brown plaque on the arm