Editing Scarlet fever (section)

===Complications===
The complications, which can arise from scarlet fever when left untreated or inadequately treated, can be divided into two categories: suppurative and nonsuppurative.<ref name=Pardo2022/>

[[Suppuration|Suppurative]] complications: These are rare complications that arise either from direct spread to structures that are close to the primary site of infection, or spread through the [[lymphatic system]] or blood. In the first case, scarlet fever may spread to the pharynx. Possible problems from this method of spread include peritonsillar or retropharyngeal abscesses, [[cellulitis]], [[mastoiditis]], or [[sinusitis]].{{citation needed|date=June 2021}}

In the second case, the streptococcal infection may spread through the [[lymphatic system]] or the blood to areas of the body further away from the pharynx. A few examples of the many complications that can arise from those methods of spread include [[endocarditis]], [[pneumonia]], or [[meningitis]].<ref name=Bennett2015>{{Cite book|title=Mandell, Douglas and Bennett's Principles and Practice of Infectious Disease, Eighth Edition|last1=Bennett|first1=John|last2=Dolin|first2=Raphael|last3=Blaser|first3=Martin|publisher=Saunders|year=2015|pages=2285–2299}}</ref>

Nonsuppurative complications: These complications arise from certain subtypes of group A streptococci that cause an autoimmune response in the body through what has been termed [[molecular mimicry]]. In these cases, the antibodies which the person's immune system developed to attack the group A streptococci are also able to attack the person's own tissues. The following complications result, depending on which tissues in the person's body are targeted by those antibodies.<ref name="Kaspar-2015"/>
* [[Acute rheumatic fever]]: This is a complication that results 2–6 weeks after a group A streptococcal infection of the upper respiratory tract.<ref name=Nelson2016/> It presents in developing countries, where antibiotic treatment of streptococcal infections is less common, as a febrile illness with several clinical manifestations, which are organized into what is called the [[Jones criteria]]. These criteria include arthritis, carditis, neurological issues, and skin findings. Diagnosis also depends on evidence of a prior group A streptococcal infection in the upper respiratory tract (as seen in streptococcal pharyngitis and scarlet fever). The carditis is the result of the immunologic response targeting the person's heart tissue, and it is the most serious sequela that develops from acute rheumatic fever. When this involvement of the heart tissue occurs, it is called [[rheumatic heart disease]]. In most cases of rheumatic heart disease, the mitral valve is affected, ultimately leading to [[Mitral valve stenosis|mitral stenosis]].<ref name="Langlois-2011"/> The link to rheumatic fever and heart disease is a particular concern in Australia, because of the high prevalence of these diseases in [[Aboriginal and Torres Strait Islander]] communities.<ref name=abcvirus/>
* [[Poststreptococcal glomerulonephritis]]: This is inflammation of the kidney, which presents 1–2 weeks after a group A streptococcal pharyngitis. 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).<ref name=Nelson2016/><ref name="Tanz-2018" /> 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.<ref name=Nelson2016/>
* 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.<ref name=Nelson2016/>