Spread of strep throat occurs by close contact, via respiratory droplets (for example, saliva or nasal discharge).[13] A person in close contact with another person infected with Group A streptococcal pharyngitis has a 35% chance of becoming infected.[18] One in ten children who are infected with Group A streptococcal pharyngitis will develop scarlet fever.[12]
Although the presentation of scarlet fever can be clinically diagnosed, further testing may be required to distinguish it from other illnesses.[7] Also, history of a recent exposure to someone with strep throat can be useful.[13] There are two methods used to confirm suspicion of scarlet fever rapid antigen detection test and throat culture.[18]
The rapid antigen detection test is a very specific test but not very sensitive. This means that if the result is positive (indicating that the Group A Strep Antigen was detected and therefore confirming that the patient has a Group A Strep Pharyngitis) then it is appropriate to treat them with antibiotics. However, if the Rapid Antigen Detection Test is negative (indicating that they do not have Group A Strep Pharyngitis), then a throat culture is required to confirm since it could be a false negative result.[26] The throat culture is the current gold standard for diagnosis.[18]
Serologic testing looks for the antibodies that the body produces against the streptococcal infection including antistreptolysin-O and antideoxyribonuclease B. It takes the body 2–3 weeks to make these antibodies so this type of testing is not useful for diagnosing a current infection. However, it is useful when assessing a patient who may have one of the complications from a previous streptococcal infection.[12][18]
Throat cultures done after antibiotic therapy can tell you if the infection has been removed. These throat swabs however are not indicated because up to 25% of properly treated individuals can continue to carry the streptococcal infection while asymptomatic.[19]
Differential diagnosis[edit] => Viral exanthem: Viral infections are often accompanied by a rash which can be described as morbilliform or maculopapular. This type of rash is accompanied by a prodromal period of cough and runny nose in addition to a fever, indicative of a viral process.[14]&Allergic or contact dermatitis: The erythematous appearance of the skin will be in a more localized distribution rather than the diffuse and generalized rash seen in Scarlet Fever.[12]&Drug eruption: These are potential side effects of taking certain drugs such as Penicillin. The reddened maculopapular rash which results can be itchy and be accompanied by a fever.[27]&Kawasaki disease Children with this disease also present with a strawberry tongue and undergo a desquamative process on their palms and soles. However these children tend to be younger than 5 years old, their fever lasts longer (at least five days) and they have additional clinical criteria (including signs such as conjunctival redness and cracked lips) which can help distinguish this from Scarlet Fever.[28]&Toxic shock syndrome: Both Streptococcal and Staphylococcal bacteria can cause this syndrome. Clinical manifestations include diffuse rash and desquamation of the palms and soles. Can be distinguished from Scarlet Fever by low blood pressure, the rash will lack sandpaper texture, and multi-organ system involvement.[29]&Staphylococcal scalded skin syndrome: This is a disease which occurs primarily in young children due to a toxin producing strain of the bacteria Staphylococcus Aureus. The abrupt start of the fever and diffused sunburned appearance of the rash can resemble Scarlet Fever. However, this rash is associated with tenderness and large blister formation. These blisters easily pop and then cause the skin to peel.[30]&Staphylococcal Scarlet Fever: The rash is identical to the streptococcal scarlet fever in distribution and texture however the skin affected by the rash will be tender.[7
Rash which has a characteristic appearance, spreading pattern, and desquamating process "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.&Then a few days later (following the desquamating process, or the shedding of the tissue which created the white coating) the whiteness disappears while the red and enlarged papillae give it the "red strawberry" appearance.[7]&Note that this involvement of the tongue is a part of the rash which is characteristic of scarlet fever.[8
Pastia's lines[9]
Lines of petechiae which appear as pink/red areas located in arm pits and elbow pit
Vomiting and abdominal pain[10]
Strep throat[edit] => Typical symptoms of streptococcal pharyngitis (also known as strep throat):[10]
Sore throat, painful swallowing&Fever - typically over 39 °C (102.2 °F)&Fatigue&Enlarged and reddened tonsils with yellow or white exudates present (this is typically an exudative pharyngitis)[11]&Enlarged and tender lymph nodes usually located on the front of the neck[12
The following symptoms will usually be absent: cough, hoarseness, runny nose, diarrhea, and conjunctivitis.[10] Their presence indicates it is more likely a viral infection.
Rash[edit] => The rash begins 1–2 days following the onset of symptoms caused by the strep pharyngitis (sore throat, fever, fatigue).[13] This characteristic rash has been denoted as "scarlatiniform" and it appears as a diffuse redness of the skin with small papules, or bumps, which resemble goose pimples.[7][14] These bumps are what give the characteristic sand paper texture to the rash. The reddened skin will blanch when you apply pressure to it. It is possible for the skin to be itchy however it will not be painful.[7] It usually first appears on the trunk and then gradually spreads out to the arms and legs.[14] The palms, soles and face are usually left uninvolved by the rash. The face is however is usually flushed, most prominent in cheeks, with a ring of paleness around the mouth.[15] After the rash spreads, it becomes more pronounced in creases in the skin, such as the skin folds in the inguinal and axillary regions of the body.[9] Also in those areas it is possible for there to be Pastia’s Lines which are petechiae arranged in a linear pattern.[9] Within 1 week of onset the rash begins to fade followed by a longer process of desquamation, or shedding of the outer layer of skin, which lasts several weeks.[12] The desquamation process usually begins on the face and progresses downward on the body.[7] After the desquamation the skin will be left with a sunburned appearance.[13]
The streptococcal pharyngitis which is the usual presentation of scarlet fever in combination with the characteristic rash commonly involves the tonsils. The tonsils will appear swollen and reddened. The palate and uvula are also commonly affected by the infection. The involvement of the soft palate can be seen as tiny red and round spots known as Forscheimer spots.[11]
Variable presentations[edit] => The features of scarlet fever can differ depending on the age and race of the person. Children less than 5 years old can have atypical presentations. Children less than 3 years old can present with nasal congestion and a lower grade fever.[16] Infants can potentially only present with increased irritability and decreased appetite.[16]
Children who have darker skin can have a different presentation in that the redness of the skin involved in the rash and the ring of paleness around the mouth can be less obvious.[7] Suspicion based on accompanying symptoms and diagnostic studies are important in these cases.
Course[edit] => Following exposure to Streptococcus, it takes 12 hours to 7 days for the onset of the symptoms. This may include fever, fatigue, and sore throat. The characteristic scarlatiniform rash then comes 12–48 hours later. During the first few days of the rash development and rapid generalization, the Pastia's Lines and strawberry tongue will also present.[7] The rash starts fading within 3–4 days followed by the desquamation of the rash which will last several weeks to a month.[13][11] 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.[17]