Ecthyma Gangrenosum

Ecthyma gangrenosum is a rare skin manifestation of a severe systemic infection most commonly caused by Pseudomonas aeruginosa, an opportunistic gram-negative bacteria. Opportunistic bacteria cause disease in individuals with compromised immune systems. Therefore, the vast majority of ecthyma gangrenosum cases occur in individuals who are critically ill or have a compromised immune system.  

Ecthyma gangrenosum typically presents with one or more skin lesions that rapidly develop into necrotic ulcers, which are open sores with an accumulation of dead tissue. Unfortunately, ecthyma gangrenosum has a high mortality rate when it’s not treated promptly. 

Ecthyma gangrenosum develops after bacteria invade small blood vessels in the skin and underlying subcutaneous tissue. Bacterial invasion usually happens due to the proliferation of a systemic infection through the bloodstream (i.e., bacteremia), but it can also occur by direct entry of bacteria through a skin wound. The infection damages the blood vessel walls, which reduces blood supply to the skin and subcutaneous tissue. This results in redness, edema, and necrosis (i.e., tissue death) of the skin, with subsequent ulcer formation.  

Traditionally, ecthyma gangrenosum has been associated with the bacteria Pseudomonas aeruginosa; however, more recently, ecthyma gangrenosum-like lesions have been reported on individuals who have other bacterial, fungal, or viral infections. Causative microorganisms include gram-positive bacteria, like Staphylococcus aureus, Streptococcus pyogenes, and Klebsiella pneumoniae; fungi, such as Mucor and Candida species; and the herpes simplex virus (HSV).  

Most of the time, ecthyma gangrenosum occurs in critically ill or immunocompromised individuals, such as people with leukemia, lymphoma, HIV infection, or severe burns, as well as in individuals receiving immunosuppressive treatment and those who have undergone bone marrow transplantation. However, it’s possible for ecthyma gangrenosum to develop in a previously healthy individual who has no other medical conditions.  

Individuals with ecthyma gangrenosum have skin lesions that begin as painless, bright or deep red patches that rapidly develop into hemorrhagic pustules, blisters filled with blood and pus. It then evolves into a gangrenous ulcer with a black scab, surrounded by a red halo. Skin lesions can transform from red patches to ulcerative, necrotic ulcers in as little as 12 to 24 hours.  

Although ecthyma gangrenosum can appear anywhere on the body, it’s most commonly found in the perineal area (i.e., the area between the genitals and the anus), buttock, lower extremities, and the armpits. Other common locations include the arms, trunk, and face.   

Severe complications can occur from ecthyma gangrenosum including osteomyelitis (i.e., bone infection) or disseminated intravascular coagulation (i.e., bleeding disorder). Individuals with systemic complications can have a toxic appearance, with possible signs and symptoms including fever, unstable vital signs, and altered level of consciousness.  

Ecthyma gangrenosum is suspected when the skin lesions have the characteristic clinical appearance; however, these lesions can easily be missed without a thorough skin examination. Diagnosis generally requires confirmation by additional tests, including blood cultures, cultures and gram stain of the wound, and skin biopsies.  

Gram stain of fluid from the wound shows many gram-negative, rod-shaped bacteria in the case of pseudomonal ecthyma gangrenosum. Tissue culture can be done to rule out the presence of any other microorganisms (e.g., other bacteria, fungi, mycobacteria) that can cause ecthyma gangrenosum-like lesions. Antibiotic sensitivity tests may be performed to determine which antibiotic will be most effective at treating the infection.  

Lastly, skin biopsy of ecthyma gangrenosum include often show signs of necrosis, or death, of the vascular tissue (i.e., necrotizing vasculitis), with few inflammatory cells and many surrounding bacteria. 

Initial medical treatment, sometimes begun prior to confirmation of the infectious agent, generally involves antibiotics that target Pseudomonas aeruginosa, including anti-pseudomonal penicillins (e.g., piperacillin/tazobactam), fluoroquinolone (e.g., ciprofloxacin or levofloxacin), third-generation cephalosporins (e.g., ceftazidime, cefepime), or carbapenems (e.g., imipenem, meropenem). Once the infectious agent and antibiotic susceptibilities are identified, the antibiotic therapy may need to be adjusted.  

In the rare cases of fungal or viral infections, treatment may include systemic antifungal therapy (e.g., azoles, amphotericin B) or specific antiviral agents.   

In cases where ecthyma gangrenosum fails to respond to medication, surgical removal of any dead, damaged, or infected tissue may be necessary to completely resolve the infection.