Erysipelas

Erysipelas (/ˌɛrəˈsɪpələs/) is a relatively common bacterial infection of the superficial layer of the skin (upper dermis), extending to the superficial lymphatic vessels within the skin, characterized by a raised, well-defined, tender, bright-red rash, typically on the face or legs, but which can occur anywhere on the skin. It is a form of cellulitis and is potentially serious.

Erysipelas is usually caused by the bacterium Streptococcus pyogenes, also known as group A, β-hemolytic streptococci, which enters the body through a break in the skin, such as a scratch or an insect bite. It is more superficial than cellulitis and is typically more raised and demarcated. The term comes from the Greek ἐρυσίπελας (erysípelas), meaning red skin.

In animals, erysipelas is a disease caused by infection with the bacterium Erysipelothrix rhusiopathiae. In animals, it is called diamond skin disease, and occurs especially in pigs. Heart valves and skin are affected. E. rhusiopathiae can also infect humans, but in that case, the infection is known as erysipeloid and is an occupational skin disease.

Symptoms often occur suddenly. Affected individuals may develop a fever, shivering, chills, fatigue, headaches, and vomiting, and be generally unwell within 48 hours of the initial infection. The red plaque enlarges rapidly and has a sharply demarcated, raised edge. It may appear swollen, feel firm, warm, and tender to touch, and have a consistency similar to orange peel. Pain may be extreme.

More severe infections can result in vesicles (pox or insect bite-like marks), blisters, and petechiae (small purple or red spots), with possible skin necrosis (death). Lymph nodes may be swollen and lymphedema may occur. Occasionally, a red streak extending to the lymph node can be seen.

The infection may occur on any part of the skin, including the face, arms, fingers, legs, and toes; it tends to favour the extremities. The umbilical stump and sites of lymphedema are also common sites affected. Fat tissue and facial areas, typically around the eyes, ears, and cheeks, are most susceptible to infection. Repeated infection of the extremities can lead to chronic swelling (lymphoedema).

Most cases of erysipelas are due to Streptococcus pyogenes, also known as group A, β-hemolytic streptococci, less commonly to group C or G streptococci and rarely to Staphylococcus aureus. Newborns may contract erysipelas due to Streptococcus agalactiae, also known as group B streptococcus or GBS.

The infecting bacteria can enter the skin through minor trauma, bites (human, insect or animal), surgical incisions, ulcers, burns, or abrasions. Underlying eczema or athlete's foot (tinea pedis) may be present, and it can originate from streptococcal bacteria in the subject's own nasal passages or ear.