Scarlet fever
Scarlet fever, also known as scarlatina and scarlatiniform rash, is an infectious disease caused by Streptococcus pyogenes, a Group A streptococcus. It most commonly affects children and young adolescents between five and 15 years of age. The signs and symptoms include a sore throat, fever, headache, swollen lymph nodes, and a characteristic rash. The face is flushed and the rash is red and blanching. It typically feels like sandpaper and the tongue may be red and bumpy. The rash occurs as a result of capillary damage by exotoxins produced by S. pyogenes. On darker-pigmented skin the rash may be hard to discern.
Scarlet fever develops in a small number of people who have strep throat or streptococcal skin infections. The bacteria are usually spread by people coughing or sneezing. It can also be spread when a person touches an object that has the bacteria on it and then touches their mouth or nose. The diagnosis is typically confirmed by culturing swabs of the throat.
There is no vaccine for scarlet fever. Prevention is by frequent handwashing, not sharing personal items, and staying away from other people when sick. The disease is treatable with antibiotics, which reduce symptoms and spread, and prevent most complications. Outcomes with scarlet fever are typically good if treated. Long-term complications as a result of scarlet fever include kidney disease, rheumatic fever, and arthritis.
In the early 20th century, scarlet fever was a leading cause of death in children, but even before World War II and the introduction of antibiotics, its severity was already declining. This decline is suggested to be due to better living conditions, the introduction of better control measures, or a decline in the virulence of the bacteria. In recent years, there have been signs of antibiotic resistance; there was an outbreak in Hong Kong in 2011 and in the UK in 2014, and occurrence of the disease rose by 68% in the UK between 2014 and 2018. Research published in October 2020 showed that infection of the bacterium by three viruses has led to more virulent strains of the bacterium.
Signs and symptoms
Scarlet fever typically presents with a sudden onset of sore throat, fever, and malaise. Headache, nausea, vomiting and abdominal pain may also be present. Scarlet fever usually follows from a group A streptococcal infection that involves a strep throat, such as streptococcal tonsillitis or more usually streptococcal pharyngitis. Often these can present together, known as pharyngotonsillitis. The signs and symptoms are therefore those of a strep throat but these are followed by the inclusion of the characteristic widespread rash. The rash usually appears one to two days later, but may appear before or up to seven days following feeling ill.It generally hurts to swallow. However, not all cases present with a fever, the degree of tiredness may vary, the sore throat and tongue changes might be slight or absent, and in some the rash can be patchy rather than diffuse. Cough, hoarseness, runny nose, diarrhea, and conjunctivitis are typically absent in scarlet fever; such symptoms indicate what is more likely a viral infection.
Mouth and throat
is usually associated with fatigue and a fever of over 39 °C. The tonsils may appear red and enlarged and are typically covered in exudate. The throat may be red with small red spots on the roof of the mouth. The uvula can look red and swollen. 30% to 60% of cases have associated enlarged and tender lymph nodes in the neck. During the first two days of illness the tongue may have a whitish coating from which red swollen papillae protrude, giving the appearance of a "white strawberry tongue". After four to five days when the white coating sheds it becomes a "red strawberry tongue". The symptomatic appearance of the tongue is part of the rash that is characteristic of scarlet fever.Rash
The characteristic rash has been denoted as "scarlatiniform", and it appears as a diffuse redness of the skin with small bumps resembling goose bumps. It typically appears as small flat spots on the neck or torso before developing into small bumps that spread to the arms and legs. It tends to feel rough like sandpaper. The cheeks might look flushed with a pale area around the mouth. The scarlet fever rash generally looks red on white and pale skin, and might be difficult to visualise on brown or black skin, in whom the bumps are typically larger, the skin looks like sandpaper, and the perioral pallor less obvious. The palms and soles are spared. The reddened skin blanches when pressure is applied to it. The skin may feel itchy, but is not painful. A more intense redness on the inside of skin folds and creases might be noticed. These are lines of petechiae, appearing as pink/red areas located in arm pits and elbow pits. It takes around a week for the main rash to disappear. This may be followed by several weeks of peeling of the skin of typically fingers and toes. The desquamation process usually begins on the face and progresses downward on the body. Sometimes, this peeling is the only sign that scarlet fever occurred. 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. After the desquamation, the skin will be left with a sunburned appearance.Variable presentations
Children younger than five years old may have atypical presentations and many of the common signs and symptoms may be missing or different. Children younger than 3 years old can present with nasal congestion and a lower grade fever. Infants may present with symptoms of increased irritability and decreased appetite.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: 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.
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.
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.
- Acute rheumatic fever: This is a complication that results 2–6 weeks after a group A streptococcal infection of the upper respiratory tract. 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. 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 stenosis. 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.
- 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. 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
Pathophysiology
The rash of scarlet fever, which is what differentiates this disease from an isolated group A strep pharyngitis, is caused by specific strains of group A streptococcus that produce a streptococcal pyrogenic exotoxin, which is mainly responsible for the skin manifestation of the infection. These toxin-producing strains cause scarlet fever in people who do not already have antitoxin antibodies. Streptococcal pyrogenic exotoxins – SPEs A, B, C, and F have been identified. The pyrogenic exotoxins, also called erythrogenic toxins, cause the erythematous rash of scarlet fever. The strains of group A streptococcus that cause scarlet fever need specific bacteriophages for there to be pyrogenic exotoxin production. Specifically, bacteriophage T12 is responsible for the production of speA. Streptococcal Pyrogenic Exotoxin A, speA, is the one most commonly associated with cases of scarlet fever that are complicated by the immune-mediated sequelae of acute rheumatic fever and post-streptococcal glomerulonephritis.These toxins are also known as "superantigens" because they can cause an extensive immune response by activating some of the cells that are mainly responsible for the person's immune system. Although the body responds to the toxins it encounters by making antibodies, those antibodies will only protect against that particular subset of toxins. They will not necessarily completely protect a person from future group A streptococcal infections, because there are 12 different pyrogenic exotoxins that may be produced by the disease, and future infections may produce a different subset of those toxins.