A 13-year-old boy is hospitalized while receiving induction therapy for acute myelogenous leukemia. During a period of profound neutropenia, he develops a fever of 39°C associated with rigors. Blood cultures are taken and he is given broad-spectrum antibiotics. Over the next 48 hours, a tender, erythematous 2 × 2 cm papule develops on his arm, the center of which becomes vesicopustular (Figure 107-1). Blood cultures from the initial febrile period are subsequently positive for Pseudomonas aeruginosa. He is treated with combination therapy including piperacillin/tazobactam and gentamicin for two weeks until neutrophil recovery.

Ecthyma gangrenosum is an infectious lesion of the skin with a characteristic necrotic center. It is seen predominantly in the immunocompromised patients related to Gram-negative bacteremia, typically Pseudomonas aeruginosa.

• Infrequent condition that is most prevalent in severely immunocompromised hosts with fever.

• The skin lesions may be a presenting feature of acute leukemia.¹

• Ecthyma gangrenosum is most commonly associated with disseminated P aeruginosa infection; however, it has also been described with other Gram-negative bacilli and fungi, including Aeromonas hydrophila, Enterobacter, Escherichia coli, Morganella, Serratia marcescens, Stenotrophomonas maltophilia, Aspergillus, Candida, Fusarium, and Mucor.^1–3

• Necrotizing, hemorrhagic vasculitis is seen on histopathology.

• Organisms are often seen, particularly within the medial blood vessel layers.^2,4

• Compromised host immunity, often from malignancy or chemotherapy, is the most significant risk factor. Neutrophil defects may also be seen.¹