A 10 y.o f presented to the ED with a rash. The patient had a recent history of several days of tactile fevers as well as URI like symptoms per the mother that resolved, but then a rash began to develop. The rash was initially on the patient’s back but then began to spread diffusely throughout the patient’s body. The patient had no complaints however since her recent viral like symptoms had resolved and the rash was not bothering her. Physical exam was remarkable for a fever of 38.3 (patient/mother unaware of this prior to arrival) as well as a diffuse erythematous blanchable rash with papules giving it a sandpaper like appearance and texture. Although she had a benign oropharyngeal exam on presentation, the patient did say she had a severe sore throat with her URI a few days prior. A rapid strep test was sent and was positive. The diagnosis of scarlet fever was made.

Scarlet Fever

Scarlet fever is a disease that can occur as a result of a group A strep infection. The signs and symptoms include a sore throat, fever, headaches, swollen lymph nodes, and a characteristic rash. The rash is red and feels like sandpaper and the tongue may be red and bumpy as well. It most commonly affects children between five and 15 years of age. 

Scarlet fever affects a small number of people who have strep throat or streptococcal skin infections. The characteristic rash is due to the erythrogenic toxin, a substance produced by some types of the bacterium. The diagnosis is typically clinical and can be confirmed by testing for strep.

Rash 

The rash has a characteristic appearance, spreading pattern, and desquamating process. It can also be associated with “Strawberry tongue.”

• The tongue starts out by having a white coating on it while the papillae of the tongue are swollen and reddened. The protrusion of the red papillae through the white coating gives the tongue a “white strawberry” appearance.
• A few days later the whiteness disappears while the red and enlarged papillae give it a “red strawberry” appearance. 

The rash typically begins 1–2 days following the onset of symptoms caused by the strep pharyngitis. This characteristic rash appears as a diffuse redness of the skin that is blanchable with small papules. The papules are small and close together giving it the characteristic sandpaper texture. The rash characteristically is:

• Blanchable
• Can be pruritic but not painful
• Appears on trunk first then gradually spreads to the periphery. The face, palms, and soles are usually spared 

Course

Following exposure to streptococcus, it takes 12 hours to 7 days for the onset of the symptoms. The characteristic rash then comes 12–48 hours later. During the first few days of rash development and rapid generalization, strawberry tongue may be present. The rash starts fading within 3–4 days, followed by the desquamation of the rash, which lasts several weeks to a month. If the case of scarlet fever is uncomplicated, recovery from the fever and clinical symptoms other than the process of desquamation occurs in 5–10 days. 

Complications

The complications which can arise from scarlet fever when left untreated or inadequately treated can be divided into two categories: suppurative and nonsuppurative.

Suppurative complications are rare. They arise from direct spread to structures which are close to the primary site of infection, which in most cases of Scarlet Fever is the pharynx. Possible problems from this method of spread include:

• peritonsillar or retropharyngeal abscesses
• cellulitis
• mastoiditis or sinusitis
• endocarditis, pneumonia, or meningitis 

Nonsuppurative complications arise from an autoimmune response. Antibodies which the person’s immune system developed to attack the group A strep also attack the person’s own tissues. These complications include:

• Acute rheumatic fever  
• Poststreptococcal glomerulonephritis
• Poststreptococcal reactive arthritis

Diagnosis

Scarlet fever is a clinical diagnosis. The diagnosis can be aided by rapid strep testing and throat culture, however apart from these there is no role for additional testing for uncomplicated scarlet fever. 

Traditionally, the rapid strep test is a very specific test but not a sensitive test. This means that if the result is negative, then a throat culture is required to confirm the negative result since it could be a false negative. A throat culture was traditionally obtained after every negative rapid strep to catch any false negatives and prevent missed diagnoses and the evolution of potential complications (rheumatic fever). 

Newer strep pharyngeal swab tests however have very high sensitivities and specificities, and a throat culture is no longer needed for these as both their sensitivities and specificities are greater than 95%. Check with your institution to see what test you use. 

Treatment

Antibiotics to combat the streptococcal infection are the mainstay of treatment for scarlet fever. Prompt administration of appropriate antibiotics decreases the length of illness and can prevent the development of complications (one of the most feared being rheumatic fever). Desquamation, however, can happen despite treatment. Post strep glomerulonephritis can also happen despite treatment.

Beta lactam antibiotics are usually first line with clindamycin and macrolides being alternative choices.

Case Resolution

This was a somewhat unusual case of scarlet fever as the patient had a slightly delayed presentation of the rash after the resolution of the URI like symptoms and sore throat (but still in the presence of fever). The rash was very typical of scarlet fever however and strep testing was positive. There were no signs of alternative diagnoses such as Kawasaki disease and there were no signs of any streptococcal complications. The patient looked well and was sent home with antibiotics and close outpatient follow-up. 

Authors:
Sumayyha Yousufi, DO
Peer reviewed and edited by:
Timothy Beau Stokes, MD