It can also develop after an episode of Impetigo or any group A streptococcal infection in the skin (this differs from acute rheumatic fever which only follows group A streptococcal pharyngitis). It is the result of the autoimmune response to the streptococcal infection affecting part of the kidney. Persons present with what is called acute nephritic syndrome, in which they have high blood pressure, swelling, and urinary abnormalities. Urinary abnormalities include blood and protein found in the urine, as well as less urine production overall. Poststreptococcal reactive arthritis: The presentation of arthritis after a recent episode of group A streptococcal pharyngitis raises suspicion for acute rheumatic fever, since it is one of the Jones criteria for that separate complication. But, when the arthritis is an isolated symptom, it is referred to as poststreptococcal reactive arthritis. This arthritis can involve a variety of joints throughout the body, unlike the arthritis of acute rheumatic fever, which primarily affects larger joints such as the knee joints. It can present less than 10 days after the group A streptococcal pharyngitis. Cause
Strep throat spreads by close contact among people, via respiratory droplets (for example, saliva or nasal discharge). A person in close contact with another person infected with group A streptococcal pharyngitis has a 35% chance of becoming infected. One in ten children who are infected with group A streptococcal pharyngitis will develop scarlet fever.
Pastias lines
Lines of petechiae, which appear as pink/red areas located in arm pits and elbow pits
Vomiting and abdominal pain

Strep throat
Typical signs and symptoms of streptococcal pharyngitis (also known as strep throat):
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)
Enlarged and tender lymph nodes usually located on the front of the neckThe following signs will usually be absent: cough, hoarseness, runny nose, diarrhea, and conjunctivitis. Such symptoms indicate what is more likely a viral infection. Rash
The rash begins 1–2 days following the onset of symptoms caused by the strep pharyngitis (sore throat, fever, fatigue). 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 bumps. These bumps are what give the characteristic sandpaper texture to the rash. The reddened skin will blanch when pressure is applied to it. The skin may feel itchy, but it will not be painful. The rash generally starts at the flexion of the elbow and other surfaces. It appears next on the trunk and gradually spreads out to the arms and legs. The palms, soles and face are usually left uninvolved by the rash. The face, however, is usually flushed, most prominently in the cheeks, with a ring of paleness around the mouth.