Definition
A characteristic symptom of scarlet fever is a conspicuous skin rash, which appears 1-3 days after infection with the bacterial pathogen Streptococcus pyogenes. Pinhead-sized, red spots, which stand out slightly from the skin surface, spread from the head and neck area over the trunk and extremities. The rash is particularly pronounced in the articular flexion and in the groin area.
If one strokes over the exanthema, a white stripe (demographism albus) forms for a short time. Also typical are a reddening of the cheeks with paleness in the mouth area and an extreme red coloration of the tongue, also called raspberry or strawberry tongue. Smallest bleedings into the uppermost skin layers can also occur, they are called petechiae, but are not specific for scarlet fever.
Causes
The rash is caused by the bacterium Streptococcus pyogenes, which has been infected by a viral bacteriophage and thus has the ability to produce an erythrogenic toxin. This toxin stimulates the body’s own defence cells and thus leads to an increased release of cytokines. Among other things, cytokines act on the vessel walls and lead to an increase in permeability there. As a result, erythrocytes can escape from the vessels and cause the visible reddish rash of the skin.
Symptoms
Scarlet fever is considered a diagnosis of gaze because of its striking appearance. However, if the rash is only slightly or not at all pronounced, a blood count or throat swab can provide information about a possible bacterial infection. The rumple-feed test is another diagnostic procedure used to detect scarlet fever.
In this test, blood is stored in the arm using an inflated blood pressure cuff. In the case of an existing infection with the toxin-producing pathogen, the increased blood pressure in the arm, under the condition of increased permeability of the vessels, leads to small bleedings in the skin. These can be indicative for the diagnosis.
The accompanying symptoms of the rash can be very diverse. The onset of the disease is very sudden. Immediately after infection, high fever and sore throat (scarlet fever) are common.
Paleness and fatigue complete the clinical picture until the rash finally appears. At this time nausea and vomiting as well as a purulent cold can also occur. Scarlet fever is a disease that is not accompanied by itching. In contrast, there are diseases such as measles or rubella, where itching is a leading symptom. A red skin rash, on the other hand, is characteristic of all these diseases.
