Scarlet Fever

Scarlet fever (SF) is a mucocutaneous eruption most commonly triggered by an erythrogenic exotoxin-producing strain of group A beta-hemolytic streptococci.
The incidence and disease associated mortality has markedly declined due to the development of antibiotics and a reduction in the virulence of disease-associated streptococci.
SF is typically seen in children in the late fall, winter, or spring.

Pathogenesis ⬆ ⬇

SF usually follows a streptococcal pharyngitis or tonsillitis but occasionally follows a wound infection, burn, or upper respiratory tract infection.
SF is most often caused by the erythrogenic toxins A, B, and C produced by group A beta-hemolytic streptococci.
Less often, an exotoxin-producing S. aureus can trigger scarlet fever.
The exotoxins lead to immune activation and the characteristic exanthem.

Clinical Manifestations ⬆ ⬇

SF typically begins with the abrupt onset of fever, sore throat, headache, and chills.
The rash begins 12 to 48 hours later as generalized blanchable erythema on the neck and chest that quickly becomes generalized. Shortly thereafter the eruption becomes finely papular, covered with tiny papules, developing a distinctive “sandpapery” or “scarlatiniform” texture (Fig. 7.19).
The skin around the mouth may show a characteristic pallor (circumoral pallor).
Linear streaks of petechiae called Pastia lines may develop in the flexures.
Mucosal findings include erythema and edema of the pharyngotonsillar area, punctate erythematous macules and petechiae on the palate, and a “strawberry tongue.”
The characteristic strawberry tongue is initially white with bright red papillae and then becomes beefy red with prominent papillae.
During the convalescent phase of the illness, the skin of the palms and soles frequently desquamates. Desquamation may be sheetlike (Fig. 7.20A,B).

Diagnosis ⬆ ⬇

The diagnosis of SF is often made on clinical grounds.
The isolation of group A streptococci from the pharynx, or the presence of elevated antistreptolysin-O titers and anti-DNase B antibodies, can help confirm the diagnosis.

Management

First-line treatment is with penicillin or amoxicillin for 10 to 14 days. Alternatives include erythromycin, cephalosporins, ofloxacin, rifampin, and newer macrolide antibiotics.
Improvement should be seen within 1 to 2 days of starting antibiotics.
Prompt and complete treatment is essential to prevent the development of rheumatic fever.
Emollients can be used to soothe the scarlatiniform eruption.

Differential Diagnosis

Streptococcal or Staphylococcal Toxic Shock Syndromes

Kawasaki Syndrome

A small vessel vasculitis characterized by fever (lasting at least 5 days), conjunctivitis, oral mucosal erythema, cervical lymphadenopathy, and erythema of the palms and soles in addition to a widespread, nonspecific eruption; lymphadenopathy.

Febrile Drug Reactions

Pink-red blanching macules and papules that begin on the face and neck and spread caudally. Eruption is itchy.
Pastia lines and strawberry tongue are not present.

Viral Exanthem

Helpful Hint

Sometimes the original streptococcal infection and eruption may have passed unnoticed and patients may seek medical attention solely for the desquamation of the palms and soles.

Other Information ⬆

Complications

Complications are uncommon but may include pneumonia, pericarditis, arthritis, meningitis, hepatitis, glomerulonephritis, and rheumatic fever.
Erythema nodosum and acute guttate psoriasis may also follow or accompany an infection with group A beta-hemolytic streptococci (see Chapter 34: Cutaneous Manifestations of Systemic Disease).
SF can recur, with reported recurrence rates as high as 18%.