These 3 dermatologic disorders often have similar characteristics. Can you tell which is which?

The conditions seen in these 3 photographs are easily confused. Can you match each picture with the correct diagnosis?1. Pityriasis rosea.
2. Pityriasis lichenoides et varioliformis acuta (PLEVA).
3. Pityriasis lichenoides chronica (PLC).

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A. Pityriasis lichenoides chronica (PLC)

This generalized papulosquamous eruption takes the form of recurrent crops of multiple small red-brown papules that are often surmounted by a platelike scale. The eruption may be mildly pruritic. Biopsy will confirm the diagnosis by showing a lymphocytic infiltrate composed of activated CD4⁺ lymphocytes. PLC may persist for months to years, although spontaneous resolution is the rule.

B. Pityriasis rosea

The hallmark of this condition is the herald patch (arrow), which is thought to be present in 40% to 60% of affected patients. The herald patch is usually a round or oval lesion and typically occurs on the upper arms or trunk (although it can occur anywhere). Development of a generalized eruption usually follows within 1 to 2 weeks. Individual lesions have a collarette scale and are normally confined to a "T-shirt and shorts" distribution (ie, they seldom appear distal to the elbows and knees or on the face). Half of patients have moderate to severe itching. Pityriasis rosea usually resolves spontaneously in about 12 weeks.

C. Pityriasis lichenoides et varioliformis acuta (PLEVA)

Like those of PLC, these lesions start as reddish brown papules; vesiculation, necrosis, and ulceration then develop, giving the lesions the distinctive appearance seen here. The eruption is usually symmetric and usually concentrated on the trunk, with lesser involvement of the proximal limbs. As with PLC, a skin biopsy confirms the diagnosis (however with PLEVA, CD8⁺ lymphocytes are seen). As the name suggests, PLEVA can resolve within weeks.