Erythropoid: causes, symptoms, diagnosis, treatment, and prognosis

Erythropoid is an infectious skin disease caused by erysipelothrix insidiosa also known as erysipelothrix rhusiopathiae, often associated with occupational exposures, mostly in the hands in contact with fish, and may be accompanied by systemic symptoms.


Causes

Erysipelothrix rhusiopathiae is the pathogen of this disease, is a Gram-positive bacillus, and is present in the soil and surfaces and intestines of fishes, swine, and birds. Horses, sheep, and goats can be infected under natural conditions. Personnel engaged in the meat and food industry, fur industry, and fisheries, veterinarians, and chefs can be infected due to injuries exposed to the bacteria.

Pathogenesis

Human infection with this disease is mainly due to exposure to contaminated pork or fish, so the incidence is related to occupation. Infections are often caused by injuries in hands. Housewives can be infected due to stab wounds or knife cuts when processing fish. However, without obvious history of trauma, persons can be infected due to simple contacts.


Signs and Symptoms

The incubation period of this disease is 2 - 7 days, minimally 8 hours, seldom more than 1 week.

According to clinical manifestations, the disease can be divided into localized erysipeloid, diffuse erysipeloid, and septic erysipeloid.

Localized erysipeloid

Localized erysipeloid is the most common in the clinical practices. Pain at the site invaded by the bacteria is followed by erythema and swelling. The most characteristic manifestation is the sharply demarcated, polygonal, purplish red skin lesion. The erythema gradually expands to the surrounding, the center partially subsides, the edges are slightly raised, forming a ring, and sometimes vesicles can occur. The lesion is generally no more than 10cm in diameter, mostly in the hands and wrists, with local burning sensation or pruritus. If the finger is involved, swelling and local skin tension can result in movement restriction. A small number of patients are accompanied by lymphangitis and lymphadenitis. Suppuration and desquamation are absent, but pigmentation after healing may be present. Fever and systemic symptoms are generally absent. If untreated, patients usually spontaneously heal 2 - 4 weeks after onset. Wandering skin lesions may be present in some patients, and new purplish red skin lesions occur next to the aged skin lesions. The erythema occurs one after another, and the skin lesions can spread to the entire hand, persisting for several months.

Diffuse erysipeloid

Diffuse erysipeloid is less common in clinical practices. Diffuse or generalized lesions may occur in the site distant from the primary infection. The morphology of skin lesions are the same as those of the localized lesions, but the inflammation is more obvious. Annular, geographic, or singular skin lesions can be present, and fever and arthritis may occur. Blood culture is negative.

Septic erysipeloid

Septic erysipeloid is clinically rare. Patients generally do not have typical skin lesions, but may develop extensive erythema and purpura. Significant systemic symptoms and long term fever can lead to endocarditis, joint pain, and a variety of visceral lesions. Positive blood culture and high mortality are present. In patients with impaired immune function, bacteremia without endocarditis can also be present.


Histopathology

There is obvious edema in the epidermis and papillary dermis, and there is inflammatory cell infiltration around the blood vessels of the dermis and subcutaneous tissues, predominantly lymphocytes, neutrophils, and plasma cells. In Gram-Weigert stain, erysipelothrix rhusiopathiae can be seen in the deep dermis, subcutaneous tissue, and perivascular areas.


Diagnosis

The bacteria can be isolated from the blood, synovial fluid, or blister fluids, and bacterial culture can help to diagnose.

Polymerase chain reaction (PCR) can help diagnose rapidly. If endocarditis is suspected, a rapid diagnosis is particularly important, because the treatment of endocarditis caused by erysipelothrix rhusiopathiae is different from the empirical treatment of endocarditis caused by Gram-positive bacillus.

Differential diagnosis

Erysipelas has the similar skin lesions with erysipeloid. Erysipelas is manifested by bright red skin lesions, obvious edema, mainly in the calves and face, and obvious systemic symptoms, whereas erysipeloid presents with mostly purplish red skin lesions, mostly in the fingers and dorsal feet, mild systemic symptoms, and a history of occupational exposure.

Cellulitis is more common in the face and trunk. Diffuse redness and swelling, pain, high fever, chills, and general malaise are present.

Erythema multiforme is without a history of trauma and occupational exposure. In addition to fingers, skin lesions can be seen in other areas.


Treatment

Localized erysipeloid

One of following antibiotics is usually used for 7 days:

  • Penicillin V or ampicillin 500mg orally once every 6 hours
  • Ciprofloxacin 250mg orally once every 12 hours
  • Clindamycin 300mg orally once every 8 hours

Cephalosporins are also effective. In vitro tests suggest daptomycin and linezolid are effective.

Erysipelothrix rhusiopathiae is resistant to sulfonamides, aminoglycosides, and vancomycin.

Diffuse and septic erysipeloid

Diffuse and septic erysipeloid can be treated with one of the following:

  • Penicillin G 2,000,000 - 3,000,000U intravenously once every 4 hours
  • Ceftriaxone 2g intravenously once a day
  • Ciprofloxacin 400mg IV q12h
  • Levofloxacin 500mg IV qd

Endocarditis is treated with penicillin G for 4 - 6 weeks. Cephalosporins and fluoroquinolones can also be selected. Vancomycin is commonly used for the empirical treatment of endocarditis caused by Gram-positive bacilli, but erysipelothrix rhusiopathiae is resistant to vancomycin. Therefore, rapid identification of erysipelothrix rhusiopathiae from other Gram-positive microorganisms is essential.


Prognosis

Most untreated patients can spontaneously heal in about 3 weeks, but few may relapse. Early application of penicillin can quickly relieve symptoms and reduce recurrences.