Rash R21.x0

Author: Prof. Dr. med. Peter Altmeyer

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Last updated on: 06.10.2023

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Exanthema diseases; Exantheme; Rash; Skin rash

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Exanthem" (from Gr. exantheo I blossom) refers to a group of infectious and non-infectious, inflammatory, temporary "skin rashes". Exanthemas are characterized by a dynamic, episodic course (either one episode or multiple episodes). They appear generalized or disseminated over larger areas, usually symmetrical(rubella, measles), rarely asymmetrical distribution (example: exanthema, unilateral laterothoracic in childhood). Exanthema is composed of different types of efflorescences (urticae, papules, vesicles, pustules). The dominant type is considered in a more detailed clinical description in the name: urticarial exanthema, macular exanthema, pustular exanthema and so on. If an exanthema course is characterized by multiple flare-ups, a "colorful" clinical aspect with different efflorescence types may appear (example: varicella exanthema).

In exanthemas in brown or black skin, the red tone of the efflorescences is absent. With a significantly more difficult diagnostic evaluation, other criteria such as anamnesis, symptomatology, distribution pattern, forms, surface design come to the forefront of the analytical evaluation.

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Due to their morphology, some exanthema are characteristic of certain viral and bacterial infections (measles, scarlet fever). Others accompany as "parainfectious" exanthems various infectious diseases (e.g. Gianotti-Crosti syndrome). Exanthema also occurs in allergic, pseudoallergic and rheumatic diseases. Exanthems can be classified according to their etiology:

    • Infectious exanthema
      • Viral exanthema (most common form of exanthema in children)
      • Bacterial and other infectious exanthema
    • Parainfectious exanthema/enzyme defects
    • Allergic/pseudoallergic exanthema
    • Idiopathic exanthema
    • Exanthema for rheumatic diseases
    • Autoimmunological exanthema
    • Toxic exanthema
    • Pseudoexanthema caused by external infections

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Exanthema can include all types of efflorescence. They usually show a synchronous monomorphism. A typical exception is varicella or PLEVA ( Pityriasis lichenoides et varioliformis acuta) with a synchronous polymorphism. Typical for varicella is the "starry sky" (several thrusts or continuous thrust activity over a longer period of time).

Differential diagnosis
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For practical reasons of differential diagnosis, exanthema diseases can also be classified according to their main age of manifestation:
  • neonatal exanthema
  • Exanthema in pre-school and school age
  • Adult exanthema.

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  • When assessing an exanthema, the first and most important step towards a valid diagnosis is the basic distinction between an infectious and a non-infectious exanthema. Careful analysis of signs of infection such as fever, AZ disorder, lymphadenopathy, hepatosplenomegaly, blood count and the evaluation of an infection scenario can help here. Only after exclusion of an infectious exanthema can a non-infectious exanthema be considered. The most frequent infectious exanthema are viral exanthema.

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  1. Föster-Holst R (2007) Virus exanthema. dermatologist 55: 804-817


Please ask your physician for a reliable diagnosis. This website is only meant as a reference.


Last updated on: 06.10.2023