This patient has the typical skin findings characteristic of Sweet syndrome, also known as acute febrile neutrophilic dermatosis. The lesions are well demarcated with a sharp cut-off separating normal and inflamed skin. Because of the intense neutrophilic inflammatory infiltrate and accompanying papillary dermal edema, the lesions are often referred to as appearing “juicy.” Patients often have a leukocytosis with a predominance of neutrophils and bands; there may be an accompanying, albeit nonspecific, elevation in inflammatory markers such as erythrocyte sedimentation rate. Patients with Sweet syndrome may have idiopathic disease (common in older white women) or paraneoplastic Sweet syndrome, most commonly seen in patients with hematologic malignancies, particularly acute myeloid leukemia or myelodysplastic syndrome. The sharply demarcated, indurated red papules, plaques, or nodules almost always develop in the setting of fever and are often mistaken for infection. Patients may develop these lesions at any time during their treatment course. Sweet syndrome may also occur as a reaction to certain medications, particularly granulocyte colony-stimulating factors. The condition is extraordinarily responsive to treatment with glucocorticoids, with the fever stopping immediately and the lesions fading within 1 to 2 days.
Candidiasis would not be expected to occur this early in this patient's neutropenic course, and the skin lesions of disseminated candidiasis are generally small red papules, sometimes with a prominent white or translucent center; plaques are not common in disseminated candidiasis.
Keratoacanthoma is a subtype of squamous cell carcinoma that often presents with an isolated, rapidly growing, red nodule with a central keratin-filled core, resembling a “volcano” with the center composed of crusted dried keratin. The “juicy” red nodule shown would be atypical for a keratoacanthoma.
Pyogenic granulomas are small, benign vascular papules that can occur almost anywhere but tend to be seen on the extremities around the nails and on the face. They tend to occur more commonly in patients treated with certain types of medications (such as certain acne medications and antiretroviral agents) and in pregnant women.
