Exanthema

Exanthema is a widespread skin eruption that results in a generalized rash. The term, derived from the Greek exanthe, is used to describe rashes that commonly accompany fever or systemic illness. Exanthems are typically caused by infectious processes, especially viruses, or by adverse drug reactions. They may be classified as infectious exanthems or drug-induced exanthems, and can vary in appearance from maculopapular to vesicular or petechial.

Clinical features often include a diffuse eruption that begins on the face or trunk and spreads to the limbs. The rash may be accompanied by fever, malaise, or lymphadenopathy, and individual morphologies can differ: maculopapular rashes are common, while vesicular (as in varicella), petechial or purpuric (in certain bacterial infections), or urticarial patterns may occur. Some exanthems have characteristic associated findings or prodromal symptoms—for example, measles with cough, coryza, and conjunctivitis; rubella with mild illness and postauricular lymphadenopathy; roseola with a fever that resolves before the rash appears.

Common causes include viral infections such as measles, rubella, erythema infectiosum (parvovirus B19), roseola, varicella, and hand-foot-and-mouth disease, as well as scarlet fever. Drug-induced exanthems, particularly morbilliform reactions, are a frequent noninfectious cause and typically develop 1–2 weeks after exposure.

Diagnosis relies on clinical history and examination, with targeted laboratory testing (e.g., serology, PCR) when the cause is unclear or complications are suspected. Management focuses on treating the underlying cause and providing supportive care, including antipyretics and antihistamines for itching. Offending medications should be stopped if a drug eruption is suspected. Seek urgent care if there are signs of systemic involvement, dehydration, high fever, altered mental status, or purpura. Prognosis is generally favorable, and most exanthems resolve without sequelae.