Scarlet fever is a disease caused by exotoxin released by Streptococcus pyogenes. Once a major cause of death, it is now effectively treated with antibiotics. The term scarlatina may be used interchangeably with scarlet fever, though it is commonly used to indicate the less acute form of scarlet fever that is often seen since the beginning of the twentieth century.
It is characterized by:
- is fine, red, and rough-textured; it blanches upon pressure.
- appears 12–48 hours after the fever.
- generally starts on the chest, armpits, and behind the ears.
- spares the face (although some circumoral pallor is characteristic).
- is worse in the skin folds. These Pastia lines (where the rash runs together in the armpits and groin) appear and can persist after the rash is gone.
- may spread to cover the uvula.
- The rash begins to fade three to four days after onset and desquamation (peeling) begins. "This phase begins with flakes peeling from the face. Peeling from the palms and around the fingers occurs about a week later." Peeling also occurs in axilla, groin, and tips of the fingers and toes.
Diagnosis of scarlet fever is clinical. The blood test shows marked leukocytosis with neutrophilia and conservated or increased eosinophils, high erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), and elevation of antistreptolysin O titer. Blood culture is rarely positive, but the streptococci can usually be demonstrated in throat culture. The complications of scarlet fever include septic complications due to spread of streptococcus in blood and immune-mediated complications due to an aberrant immune response. Septic complications -- today rare -- include ear and sinus infection, streptococcal pneumonia, empyema thoracis, meningitis and full-blown sepsis, upon which the condition may be called malignant scarlet fever.
Immune complications include acute glomerulonephritis, rheumatic fever and erythema nodosum. The secondary scarlatinous disease, or secondary malignant syndrome of scarlet fever, includes renewed fever, renewed angina, septic ear, nose, and throat complications and kidney infection or rheumatic fever and is seen around the eighteenth day of untreated scarlet fever.
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