February 09, 2007

NSI, Staphylococcal Scalded Skin Syndrome


Necrotizing Skin Infections(NSI), including necrotizing cellulitis and necrotizing fasciitis, are severe forms of cellulitis characterized by death of infected tissue (necrosis).

Most skin infections do not result in death of skin and nearby tissues. Sometimes, however, bacterial infection can cause small blood vessels in the infected area to clot. This clotting causes the tissue fed by these vessels to die from lack of blood. Because the body's immune defenses that travel through the bloodstream (such as white blood cells and antibodies) can no longer reach this area, the infection spreads rapidly and may be difficult to control. Death is not uncommon, even with appropriate treatment.

Some necrotizing skin infections spread deep in the skin along the surface of the muscle (fascia) and are termed necrotizing fasciitis. Other necrotizing skin infections spread on the outer layers of skin and are termed necrotizing cellulitis. Several different bacteria, such as Streptococcus and Clostridia, may cause necrotizing skin infections, although in many people the infection is caused by a combination of bacteria. The streptococcal infection in particular has been termed "flesh-eating disease" by the lay press, although it differs little from the others.

Some necrotizing skin infections begin at puncture wounds or lacerations, particularly wounds contaminated with dirt and debris. Other infections begin in surgical incisions or even healthy skin. Sometimes people with diverticulitis, intestinal perforation, or tumors of the intestine develop necrotizing infections of the abdominal wall, genital area, or thighs. These infections occur when certain bacteria escape from the intestine and spread to the skin. The bacteria may initially create an abscess in the abdominal cavity and spread directly outward to the skin, or they may spread through the bloodstream to the skin and other organs.

Symptoms and Diagnosis

Symptoms often begin just as for cellulitis. The skin may look pale at first, but quickly becomes red or bronze and warm to the touch, and sometimes becomes swollen. Later, the skin turns violet, often with the development of large fluid-filled blisters (bullae). The fluid from these blisters is brown, watery, and sometimes foul smelling. Areas of dead skin (gangrene) turn black. Some types of infection, including those produced by Clostridia and mixed bacteria, produce gas. The gas creates bubbles under the skin and sometimes in the blisters themselves, causing the skin to feel crackly when pressed. Initially the infected area is painful, but as the skin dies, the nerves stop working and the area loses sensation.

The person usually feels very ill and has a fever, a rapid heart rate, and mental deterioration ranging from confusion to unconsciousness. Blood pressure may fall because of toxins secreted by the bacteria and the body's response to the infection (septic shock ).

A doctor makes a diagnosis of necrotizing skin infection based on its appearance, particularly the presence of gas bubbles under the skin. X-rays may show gas under the skin as well. The specific bacteria involved are identified by laboratory analysis of infected fluid and tissue samples. However, treatment must begin before a doctor can be certain which bacteria are causing the infection.

Treatment and Prognosis

The treatment for necrotizing fasciitis is intravenous antibiotic therapy and surgical removal of the dead tissue. Large amounts of skin, tissue, and muscle must often be removed, and in some cases, an affected arm or leg may have to be amputated. People with necrotizing infections caused by anaerobic bacteria (for example, Clostridium perfringens may benefit from treatment in a high-pressure (hyperbaric) oxygen chamber.

The overall death rate is about 30%. Older people, those who have other medical disorders, and those in whom the disease has reached an advanced stage have a poorer outcome.

Staphylococcal Scalded Skin Syndrome

Staphylococcal scalded skin syndrome is a reaction to a staphylococcal skin infection in which the skin peels off as though burned.

Certain types of staphylococci bacteria secrete toxic substances that cause the top layer of the epidermis to split from the rest of the skin. Because the toxin spreads throughout the body, staphylococcal infection of a small area of skin may result in peeling over the entire body. Staphylococcal scalded skin syndrome occurs almost exclusively in infants, young children, and people with a weakened immune system. Like other staphylococcal infections, staphylococcal scalded skin syndrome is contagious.


Symptoms begin with an isolated, crusted infection that may look like impetigo. In newborns, the infection may appear in the diaper area or around the stump of the umbilical cord. In adults, the infection may begin anywhere. In all people with this disorder, scarlet-colored areas appear around the crusted area within a day of the beginning of infection. These areas may be painful. Then, other large areas of skin distant from the initial infection redden and develop blisters that break easily.

The top layer of the skin then begins peeling off, often in large sheets, with even slight touching or gentle pushing. Within another 1 to 2 days, the entire skin surface may be involved, and the person becomes very ill with a fever, chills, and weakness. With the loss of the protective skin barrier, other bacteria and infective organisms can easily penetrate the body, causing what doctors call superinfections. Also, critical amounts of fluid can be lost because of oozing and evaporation, resulting in dehydration.

Diagnosis and Treatment

A diagnosis is made by the appearance of skin peeling after an apparent staphylococcal infection. If no signs of staphylococcal infection are observed, doctors often perform a biopsy, in which a small piece of skin is removed, examined under a microscope, and sent to the laboratory to be cultured for bacteria.

Antibiotics given intravenously, such as nafcillin or cefazolin , are started quickly. Treatment continues for at least 10 days. With early treatment, healing takes 5 to 7 days.

The skin must be protected to help prevent further peeling; it should be treated as if it were burned

Adapted from: Merck & Co., Inc