Fever and Rash
A fever is one sign of the body’s defense response. A fever occurs when a pyrogen, a toxin, or cytokine produced by an infectious agent, human tissue, or a medication acts on the anterior hypothalamus to increase the body’s temperature set point. Because fever can occur as a nonspecific response associated with a variety of illnesses, both infectious and noninfectious, other clues are used to determine the underlying cause. Oftentimes, a concurrent rash can help clinch the diagnosis. Fever and rash can occur as a result of an infection, a reaction to a medication, or a systemic illness. A thorough and complete history and physical examination is essential to determine the underlying etiology.
There are a number of different types of rashes that can occur with fevers. Observing the specific morphology, associated clinical features, distribution, and natural history of the eruption can aid in the diagnosis. Occasionally, fever and rash can be the presenting features of a life-threatening illness and these require immediate intervention (see GENERALIZED ERUPTIONS). In this chapter, some of the most common rashes that occur with fever are outlined by morphology of the eruption, their typical distribution, natural history, and associated symptoms are presented to serve as an aid in the diagnosis.
Morbilliform eruptions are composed of pink to red discrete macules and slightly raised papules that oftentimes have a peripheral blanched halo. The most common causes of fever and morbilliform eruptions can be seen in the setting of an infection, a drug reaction, or a systemic illness; the most common associations are listed below.
Nonspecific Viral Exanthem
Most often caused by non-polio enteroviruses and respiratory viruses (adenovirus, rhinovirus, parainfluenza virus, respiratory syncytial virus, influenza virus).
Generalized (Fig. 21.1)
Mostly trunk and extremities, less often the face
Begins after prodrome of fever and malaise
Heals spontaneously in 1 to 3 weeks
Usually preceded by fever and prodromal symptoms including malaise, rhinorrhea, cough, or gastrointestinal complaints
The eruption itself is usually not itchy but appears redder and/or raised after a hot bath or heat
Supportive, mid- to low-potency topical steroids can be used to help with symptoms and shorten the course
Occurs in infants and unvaccinated children
Caused by an RNA Paramyxoviridae family virus
Decreased incidence worldwide but recent increased incidence in unvaccinated groups (infants <1 year, groups that defer vaccination, etc.)
Figure 21-2 Rubeola, measles.
Pink red macules and papules on the face, trunk, and extremities in an infant with measles.
Rash appears 3 to 5 days after prodrome
Spreads over 3 days
Resolves in 2 to 5 days
Prodrome of malaise, headache, and fever
The three “C’s”: cough, coryza, and conjunctivitis
Enanthem presents as punctate whitish gray spots on an erythematous base on buccal mucosa (Koplik spots)
Oral vitamin A supplementation in malnourished patients
Rubella (German Measles)
Occurs in unvaccinated populations
Caused by small RNA virus of the togavirus family
Also called “3-day measles”
First appears on face, then spreads downward to trunk and extremities (Fig. 21.4)
Becomes generalized within 24 hours
Rash lasts an average of 3 days but may be up to 8 days
Mild nonexudative conjunctivitis and an enanthem on the soft palate (Forchheimer spots) may occur
Arthritis and arthralgias most often of knees, wrists, and fingers may persist for a month or more
Figure 21-4 Rubella, German measles.
Pink red macules on the face and trunk. Rubella has been referred to as “3-day measles.”
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Roseola (Exanthem Subitum)
Occurs in infants and young children; also referred to as the sixth disease
Caused by human herpesvirus 6 (HHV-6)
Symptoms vary from absent to the classic presentation of a high fever of rapid onset followed by a rash
Starts on trunk, neck, and behind the ears and spreads to extremities
Pale pink macules progress to become confluent (Fig. 21.5)
Spares face and distal extremities
High fever for 3 days
Followed by typical rash
Resolves in 24 to 48 hours
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