SAMIR S. SHAH
DEFINITION OF THE COMPLAINT
The complaint of fever accounts for a large portion of ambulatory pediatric visits. While classically defined as a temperature greater than 38.0°C for neonates and greater than 38.5°C for older children, the term “fever” is subject to significant interpretation. An isolated temperature measurement of 38.0°C in a toddler may not be meaningful; however recurrent daily temperatures of 38.0°C during a period of several weeks may indicate an underlying pathology.
Practitioners must also remember that body temperature normally fluctuates throughout the day. Body temperature tends to be lower in the early morning and peaks in the evening. Certain conditions or activities, such as exercise, warm baths, or hot drinks, also affect the measured temperature. Additionally, temperature values of axillary measurements may be 0.5°C-1.0°C lower than oral, rectal, or tympanic measurements. To compensate for such discrepancies, parents are sometimes instructed to add 0.5°C or 1.0°C to axillary measurements to approximate the “real” temperature. Such “corrections” may further cloud evaluation of the febrile child.
COMPLAINT BY CAUSE AND FREQUENCY
Fever may develop in response to injury, infection, autoimmune disease, or malignancy. The release of endogenous pyrogens triggers a cascade of reactions that ultimately raise the hypothalamic set-point. Fever may also be caused when the body’s heat production or environmental heat overwhelms heat loss mechanisms or when heat loss mechanisms are deficient. Viruses are the most common cause of fever in children. Specific common causes of fever are too numerous to list here but less common causes of fever are listed in Table 11-1.
TABLE 11-1. Less common causes of fever.
The clarifying questions listed below may help provide clues to the diagnosis.
• What temperature value is the parent using to define a fever?
—While 98.6°F is commonly considered the normal body temperature, normal body temperature exhibits significant daily variation with a nadir in the early morning and a peak in the early evening.
• Are there symptoms of specific illness?
—The presence of certain complaints such as bloody diarrhea, cough, and stiff neck suggests specific diagnostic categories.
• Is there exposure to animals?
—Animal exposure refers not only to pets within the home but also to contact with animals owned by the school or by friends and acquaintances. Inquire about contact with rodents and farm animals as well as consumption of unpasteurized dairy products and raw or undercooked meats. For example, exposure to house mice may suggest lymphocytic choriomeningitis virus, while exposure to farm animals suggests brucellosis as a potential cause. The animal-exposure history should also elicit participation in recreational activities such as hunting or triathlons that include a fresh-water swimming component. An outbreak of leptospirosis, a cause of prolonged fever, occurred in athletes and community residents following a triathlon; 11% of triathletes and 6% of community residents contracted leptospirosis. Household contacts with occupational exposure to potentially infectious animals should also be sought.
• Were there recent tick bites?
—Tularemia, ehrlichiosis, anaplasmosis, Rocky Mountain spotted fever, babesiosis, and Lyme disease may be acquired in this manner.
• Was there any recent travel?
—Travel to regions where certain diseases are endemic may shift the differential diagnosis. For example, travel to the Indian subcontinent raises the suspicion for typhoid fever, and malaria. Coccidioidomycosis would be included in the differential diagnosis of a child with atypical pneumonia who has traveled to the Southwestern United States.
• What medications is the child receiving?
—Medications may cause fever. Some of the most common mechanisms include altered thermoregulatory regulation (e.g., cimetidine, anticholinergic agents) and idiosyncratic reactions. Medications commonly implicated as a cause of fever include penicillins, cephalosporins, acetaminophen, anticonvulsants, and methylphenidate. Medication-related fever may occur any time after initiation of therapy but typically occurs within 1-2 weeks of medication initiation. Children with medication-related fever typically appear well rather than ill.
• What is the pattern of fever?
—The evaluation of acute, prolonged, and recurrent fevers differs dramatically. When distinguishing between prolonged and recurrent fevers is difficult, documenting the fevers in a “fever diary” may help clarify the pattern. It is also important to clarify the method used (“felt warm” vs. actual measurement), duration of thermometer insertion, location (tympanic membrane, oral, axillary, or rectal), time of day, and whether the elevated temperature—in cases of prolonged fever or fever of unknown origin—was confirmed by more than one person.
• What is the patient’s ethnicity?
—Some causes of recurrent fever occur more commonly among certain ethnic groups: familial Mediterranean fever (Armenian, Arab, Turkish, Sephardic Jews), Hyper-IgD (Dutch, French), and tumor necrosis factor receptor-associated periodic fever syndrome (TRAPS) (Irish, Scottish).
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