eMedicine Specialties > Dermatology > Bacterial Infections

Scarlet Fever

Author: Edward J Zabawski Jr, DO, RPh, Dermatologist, Spencer Dermatology Group
Contributor Information and Disclosures

Updated: Apr 28, 2009

Introduction

Background

Scarlet fever is an infection caused by toxin-producing group A beta hemolytic streptococci (GABHS) found in secretions and discharge from the nose, ears, throat, and skin. Scarlet fever may follow streptococcal wound infections or burns, as well as upper respiratory tract infections, but food-borne outbreaks have been reported.^1,2

Pathophysiology

As the name scarlet fever implies, an erythematous eruption is associated with a febrile illness. The circulating toxin, often referred to as erythemogenic toxin, causes the rash as a consequence of local production of inflammatory mediators and alteration of the cutaneous cytokine milieu. This results in a sparse inflammatory response and dilatation of blood vessels, leading to the characteristic scarlet color of the rash.³

Mortality/Morbidity

Historically, scarlet fever resulted in death in 15-20% of those affected. Since the advent of antibiotic therapy, the mortality rate for scarlet fever is less than 1%. Although uncommon, case reports describe patients, including adults, who are severely affected.⁴ Morbidity and mortality associated with scarlet fever is usually minimal. Known complications, such as septicemia, vasculitis, hepatitis, or rheumatic fever, should be considered on a case-by-case basis as determined by the presence of clinical history and examination findings suggestive of those diseases.^5,6 Localized soft tissue infections may suggest the presence of underlying osteomyelitis, but scarlet fever may occur from cellulitis alone.⁷ When scarlet fever has been determined to be due to a soft tissue infection over or near bone, evaluation for bony involvement should be considered.

Race

No racial or ethnic predilection is reported for group A streptococcal infection.

Age

The infection usually occurs in children, with peak age incidence from 1-10 years. However, it can occur in older children and adults.

Leslie et al suggest from a case-control study that antecedent streptococcal infection can increase the likelihood of children developing certain neuropsychiatric disorders, including Tourette syndrome, attention-deficit/hyperactivity disorder, and major depressive disorder.⁸

Clinical

History

The cutaneous eruption of scarlet fever accompanies a streptococcal infection at another anatomic site, usually the tonsillopharynx. Abrupt onset of fever, headache, vomiting, malaise, chills, and sore throat occurs. Rash appears 1-4 days after the onset.

Physical

The mucous membranes usually are bright red, and scattered petechiae and small red papular lesions on the soft palate are often present.

• During the first days of infection, the tongue is heavily coated with a white membrane through which edematous red papillae protrude (classic appearance of white strawberry tongue).
• By day 4 or 5, the white membrane sloughs off, revealing a shiny red tongue with prominent papillae (red, strawberry tongue).
• Red, edematous, exudative tonsils, as shown below, are typically observed if the infection originates in this area.
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    The exudative pharyngitis typical of scarlet fever. Although the tongue is somewhat out of focus, the whitish coating observed early in scarlet fever is visible.

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    The exudative pharyngitis typical of scarlet fever. Although the tongue is somewhat out of focus, the whitish coating observed early in scarlet fever is visible.

• The characteristic exanthem consists of a fine erythematous punctate eruption that appears within 1-4 days following the onset of the illness. It first appears on the upper trunk and axillae and then becomes generalized, although it is usually more prominent in flexural areas, such as the axillae, popliteal fossae, and inguinal folds. It may also appear more intense at dependent sites and sites of pressure, such as the buttocks.
• Capillary fragility is increased, and often, transverse areas of hyperpigmentation with petechiae in the axillary, antecubital, and inguinal areas (Pastia lines) can be observed.
• The face is usually flushed, and circumoral pallor is observed.
• The eruption imparts a dry rough texture to the skin that is reported to resemble the feel of sandpaper.
• The cutaneous rash, shown below, lasts for 4-5 days, followed by fine desquamation, the extent and duration of which is directly related to the severity of the eruption.
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    Desquamation of the palms is a frequently observed self-limited manifestation of scarlet fever present in the healing period following resolution of the infection and acute eruption.

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    Desquamation of the palms is a frequently observed self-limited manifestation of scarlet fever present in the healing period following resolution of the infection and acute eruption.

Causes

The overwhelming majority of cases of scarlet fever are caused by beta hemolytic Lancefield group A streptococcus (GABHS). Other bacteria can cause a pharyngitis and similar rash, such as Staphylococcus aureus, Haemophilus influenzae, Arcanobacterium haemolyticum, and Clostridium species.⁹ Differential diagnosis includes other causes of fever accompanied by erythematous eruptions. Recurrent cases of scarlet fever have been reported from reinfection with strains unrelated to Streptococcus pyogenes.¹⁰

• The cutaneous eruption of fifth disease may be confused with that of scarlet fever, but the affected child is usually well and afebrile.
• Rubella and rubeola may appear similar, but the presence of conjunctivitis, purulent rhinitis, and cough are helpful clues to the diagnosis of rubeola. In addition, the eruption of rubeola usually begins behind the ears and on the scalp and forehead, not on the torso. Rubella typically begins on the head and face.
• Other viral exanthemata, such as those caused by Epstein-Barr virus (infectious mononucleosis), enterovirus, hepatitis B infection, HIV, and Streptobacillus moniliformis infection (rat bite fever) may also need to be considered.
• Other bacteria-associated syndromes with cutaneous eruptions (eg, toxic shock syndrome, secondary syphilis) may appear similar to scarlet fever, but the presence of vasomotor instability and ischemic necrosis of digits in the former and palmoplantar involvement with positive serology in the latter should allow for distinction.
• Noninfectious diseases that should be considered include Kawasaki disease, acute lupus erythematosus, morbilliform drug eruption, and juvenile rheumatoid arthritis.

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