Differentials
Lymphomatoid papulosis
SIGNS / SYMPTOMS
Lymphomatoid papulosis can clinically resemble pityriasis lichenoides, the pityriasis lichenoides et varioliformis acuta subtype, yet the lesions are more nodular as opposed to papular. Unlike pityriasis lichenoides, it presents around the fifth decade and has a higher likelihood to develop into cutaneous lymphoma.[20]
INVESTIGATIONS
Skin biopsy will show nodular infiltrate of atypical lymphocytes (some CD30+ with epidermotropism).[20]
Guttate psoriasis
SIGNS / SYMPTOMS
Clinical exam of multiple pink flat papules with prominent scale mostly scattered on the torso differentiates this entity from pityriasis lichenoides.[1]
Drug eruption
SIGNS / SYMPTOMS
Clinical exam of generalized pink-to-red macules and papules, usually absent of scale, crust, or ulceration, and history of recent medication changes.
INVESTIGATIONS
No differentiating tests recommended; drug eruption is a clinical diagnosis.
Syphilis infection (secondary)
SIGNS / SYMPTOMS
History of sexual activity and possible primary chancre. Polymorphic, multiple, pink-to-brown macules and papules in a diffuse distribution on clinical exam. Frequent involvement of palms and soles and accompanying mucosal ulcers.
INVESTIGATIONS
Venereal disease research laboratory/rapid plasma reagin tests are positive.
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