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Scarlet Fever

rash bacteria red disease

Scarlet fever (sometimes called scarletina), is a bacterial disease, so named because of its characteristic bright red rash. Before the twentieth century, and the age of antibiotics, scarlet fever (at one time called "the fever") was a dreaded disease and a leading cause of death in children. The disease is caused by a group A beta-hemolytic streptococcus bacteria (genus Streptococcus pyogenes), the same bacteria that cause tonsillitis and streptococcal pharyngitis ("strep throat"). Scarlet fever occurs when group A streptococcal pharyngitis is caused by a lysogenic strain of the streptococcus bacteria that produce a pyrogenic exotoxin (erythrogenic toxin), which causes the rash.

Current research suggests that the erythrogenic toxin produced by the bacteria is actually one of three exotoxins, called streptococcal pyrogenic exotoxins A, B, and C. Some people possess a neutralizing antibody to the toxin and are protected from the disease. So, if a person has "strep throat," scarlet fever can develop only if the infecting bacteria is an erythrogenic toxin producer, and if the person lacks immunity to the disease.

The first stage of scarlet fever is essentially "strep throat" (sore throat, fever, headache, sometimes nausea and vomiting). The second stage, which defines, or provides, the diagnosis for scarlet fever, is a red rash appearing two to three days after the first symptoms. Areas covered by the rash are bright red with darker, elevated red points, resembling red "goose pimples" and having a texture like sandpaper. The tongue has a white coating with bright red papillae showing through, later becoming a glistening "beefy" red (strawberry or raspberry tongue). The rash, which blanches (fades) with pressure, appears first on the neck and then spreads to the chest, back, trunk, and then extremities. The extent of the rash depends on the severity of the disease. The rash does not appear on the palms or soles of hands and feet, nor on the face, which is brightly flushed with a pale area circling the mouth (circumoral pallor). The rash usually lasts four to five days and then fades away. The red color of the rash is due to toxic injury to the tiny blood vessels in the skin, causing them to dilate and weaken. Another characteristic of scarlet fever is the peeling of skin (desquamation) after the rash fades away. The peeling occurs between the 5th-25th day, starting with a fine scaling of the face and body, and then extensive peeling of the palms and soles. The outer layer of skin, damaged as a result of the erythrogenic toxin, is replaced by new skin growth at the intermediate level of the epidermis (skin).

The disease is usually spread from person to person by direct, close contact or by droplets of saliva from sneezing or coughing. Therefore, scarlet fever can be "caught" from someone who has only streptococcal pharyngitis. Scarlet fever is most common among children, although any age is susceptible. Scarlet fever can also develop because of group A streptococcal infection in a wound, or from food contaminated by the same bacteria. Today, scarlet fever is not a common occurrence, most likely due to early treatment of "strep throat" and possibly because antibiotics have made their way into the food chain. Complications and treatment of scarlet fever are the same as with streptococcal pharyngitis, but have also become uncommon due to the widespread use of antibiotics.

Penicillin is the drug of choice unless the infected person is allergic to it. After 24 hours of treatment with penicillin, the infected person is no longer contagious, but the patient should take the antibiotic for ten days to ensure total eradication of the bacteria. If left untreated, suppurative (pus-forming) complications such as sinusitis, otitis media (middle ear infection), or mastoiditis (infection of the mastoid bone, just behind the ear), can occur. Treatment of scarlet fever is especially important to prevent nonsuppurative complications such as acute rheumatic fever or acute glomerulonephritis (inflammation of the kidneys).


Resources

Books

Cormican, M.G., and M.A. Pfaller. "Molecular Pathology of Infectious Diseases," in Clinical Diagnosis and Management by Laboratory Methods. 20th ed. Philadelphia: W. B. Saunders, 2001.

Mandell, Gerald L., ed. Principles and Practice of Infectious Diseases. 4th ed. New York: Churchill Livingstone, 1994.

Textbook of Medicine. 19th ed. Philadelphia: W.B. Saunders, 1994.


Christine Miner Minderovic

KEY TERMS

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Beta-hemolytic

—One of three types of hemolytic reactions on a blood agar medium. Beta-hemolytic produces a clear zone around a colony of bacteria.

Erythrogenic

—Producing erythema, a redness of the skin, produced by the congestion of the capillaries.

Group A streptococcus

—A serotype of the streptococcus bacteria, based on the antigen contained in the cell wall.

Lysogenic

—Producing lysins or causing lysis (dissolution).

Pyogenic

—Pus-producing.

Pyrogenic

—Fever-producing.

Streptococcus

—A genus of microorganism. The bacteria are gram-positive spheres that grow in a chain. Classification depends on antigenic composition, pattern of hemolysis observed on a blood agar growth plate, growth characteristics, and biochemical reactions.

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