Case Letter

Sweet Syndrome With Marked Eosinophilic Infiltrate

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Practice Points

  • This report highlights a case of classical Sweet syndrome (SS) with a particularly dense eosinophilic infiltrate, which could be mistaken for other eosinophilic dermatoses.
  • Dermatologists should be aware of the possibility of marked eosinophilic infiltration in all subtypes of SS.



To the Editor:

Sweet syndrome (SS), also known as acute febrile neutrophilic dermatosis, is an uncommon inflammatory skin disorder characterized by sudden onset of fever, leukocytosis, neutrophilia, and tender erythematous papules or plaques or both. Skin biopsy usually reveals extensive infiltration of neutrophils into the epidermis and dermis.1-3 Although rare, cases of eosinophil-rich SS have been reported in patients with drug-induced and malignancy-associated SS.4,5 We report a case of a patient with classical SS with dermal eosinophilic infiltration.

An 80-year-old Hispanic man presented with abrupt onset of a rash on the posterior scalp, left ear, back, and hands of 5 days’ duration. The lesions were painful and had progressed to the point of impairing hand grip. The patient’s medical history included a reported common cold the week prior, hyperlipidemia, and hypertension, for which he took metoprolol, simvastatin, aspirin, and clopidogrel. He denied oral lesions and medication changes. He was afebrile and did not experience dietary changes, weight loss, or fatigue. He recently returned from travel to the Dominican Republic.

Physical examination revealed tender, well demarcated, pink to violaceous, pseudovesicular papules and plaques on the palms and dorsal hands (Figure 1), the posterior scalp, left ear, proximal left arm, and back. Pink, juicy, targetoid papules were also found on the scalp, back, and left arm. There was no evidence of lymphadenopathy. Laboratory test results revealed an elevated white blood cell count (11,500/µL [reference range, 3800-10,800/µL]), absolute neutrophil count (8073/µL [reference range, 1500–7800/µL]), and eosinophil count (610/µL [reference range, 15–500/µL]). These results indicated leukocytosis with neutrophilia and mild eosinophilia. The patient also was anemic (hemoglobin, 11.5 g/dL [reference range, 13.2–17.1 g/dL]; hematocrit, 35.1% [reference range, 38.5%–50%]). Urine testing revealed altered renal function (serum creatinine, 2.42 mg/dL [reference range, 0.7–1.1 mg/dL]; blood urea nitrogen, 34 mg/dL [reference range, 7–25 mg/dL]; glomerular filtration rate, 4 mL/min/1.73 m2 (reference range, ≥60 mL/min/1.73 m2]), suggesting stage 4 chronic kidney disease. Urinalysis showed mild hematuria and proteinuria.

Figure 1. Sweet syndrome. A, Well-demarcated violaceous papules and plaques on both palms. B, Rash on the dorsal hands that was described by the patient as tender and affecting hand grip

Histopathology of biopsies taken from plaques on the left arm and lower back revealed a dense neutrophilic infiltrate with numerous scattered eosinophils in the dermis. Some neutrophils were intact; others were fragmented without evidence of vasculitis. A subtle subepidermal edema also was noted (Figure 2). A diagnosis of SS was made.

Figure 2. Sweet syndrome. A and B, Dense neutrophilic infiltrate dissecting collagen fibers in the superficial and deep dermis (H&E, original magnifications ×4 and ×10). C, Associated dermal eosinophils also were noted (H&E, original magnification ×20).

Initial treatment included prednisone (40 mg daily, tapered by 5 mg every 3 days) and erythromycin (500 mg 4 times daily) for 7 days because of suspected Mycoplasma infection. The rash resolved in 1 week. No recurrence was noted during 4 months of follow-up. The white blood cell count returned to within reference range (8400/µL), ruling out the possibility of a smoldering myeloid process.

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