Remittent fever
Remittent fever is a pattern of fever in which body temperature rises and falls daily, typically by 0.3°C to 1.4°C, but never returns to normal levels (below 37.2°C or 99°F).[1][2] This distinguishes it from intermittent fever, where temperature periodically returns to normal, and from continuous fever, which remains steadily elevated without significant daily variation.[3] The pattern is not diagnostic on its own but often signals an underlying infectious or inflammatory process, with symptoms including chills, sweats, and general malaise alongside the fluctuating temperature.[1]Characteristics and Patterns
Remittent fever exhibits daily amplitude variations, commonly between 0.3°C and 1.4°C in milder forms, though "hectic" variants can fluctuate more widely (≥1.4°C).[1] Clinically, it may evolve from an initial intermittent pattern into a more sustained elevation if untreated, and temperature charting over several days is essential for identification.[3] Unlike sustained fevers, the diurnal rhythm persists, with peaks often in the late afternoon or evening, reflecting the body's hypothalamic response to pyrogens such as cytokines released during infection.[2]Causes and Associated Conditions
The most common causes of remittent fever are bacterial infections, including pneumonia, typhoid fever, pyelonephritis, brucellosis, rickettsial infections, and infective endocarditis.[2][1] It is also frequently linked to abscesses, ascending cholangitis, and other pyogenic processes, as well as tuberculosis and certain malignancies like lymphomas or hypernephromas.[1] Non-infectious etiologies, such as drug reactions or autoimmune conditions, can occasionally produce this pattern, though infections predominate in acute cases.[3] In tropical regions, it may indicate other vector-borne diseases like certain rickettsial infections.[2]Diagnosis and Management
Diagnosis relies on a thorough history, physical examination, and laboratory tests to identify the underlying cause, as the fever pattern alone rarely specifies the etiology.[3] Blood cultures, imaging, and serologic assays are often employed, particularly for suspected bacterial or parasitic origins.[1] Treatment focuses on addressing the root condition—such as antibiotics for bacterial infections or antimalarials for parasitic causes—while antipyretics like acetaminophen or ibuprofen provide symptomatic relief by reducing temperature spikes.[3] Early intervention is critical, as prolonged remittent fever can lead to complications like dehydration or sepsis if the primary disease progresses.[2]Definition and Classification
Definition
Remittent fever is a distinctive pattern of fever characterized by daily fluctuations in body temperature that do not return to normal baseline levels, typically remaining above 37.2°C (99°F) throughout the day.[1] Unlike other fever types, the temperature rises and falls but stays persistently elevated, reflecting ongoing physiological response without complete resolution.[3] The amplitude of these daily variations typically ranges from 0.3°C to 1.4°C, with more pronounced swings classified as hectic fever if exceeding 1.4°C; note that classifications vary, with some sources describing fluctuations exceeding 2°C.[1][2] This pattern often accompanies systemic symptoms such as chills, sweats, and malaise, highlighting its role as a clinical indicator of underlying inflammatory or infectious processes.[1] The term "remittent fever" originated in the 19th century, when physicians used it to describe fevers without return to normal temperature, shifting focus in modern medicine to the diurnal variation without normalization.[4] It commonly manifests in diseases like typhoid fever.[2]Comparison with Other Fever Patterns
Remittent fever is characterized by daily temperature fluctuations exceeding 1°C while remaining persistently above the normal baseline (typically >37.2°C), distinguishing it from other fever patterns through its incomplete diurnal remission.[5] Note that classifications of fever patterns, including fluctuation amplitudes, vary across medical literature and are not always diagnostic on their own.[3] In contrast, intermittent fever features spikes of elevated temperature that return fully to normal levels (≤37.2°C) between episodes, often on a daily or periodic basis, as seen in the quotidian pattern of malaria where paroxysms occur every 24 hours followed by euthermia.[6] This return to baseline allows for clear afebrile intervals, unlike the sustained elevation in remittent fever. Continuous or sustained fever maintains an elevated temperature with minimal variation (<1°C over 24 hours), lacking the noticeable diurnal swings of remittent patterns; examples include typhoid fever or typhus, where the temperature plateaus without significant drops.[7] Relapsing fever, however, involves episodic high fevers recurring after prolonged afebrile periods of several days to weeks, driven by antigenic variation in pathogens like Borrelia species in borreliosis, creating a cyclic pattern absent in the more consistent daily undulations of remittent fever.[8] Saddleback or biphasic fever presents as two distinct peaks of elevation separated by a partial remission that does not reach normal levels, often over several days, as observed in dengue infections; this contrasts with remittent fever's ongoing, non-biphasic fluctuations without such defined dual phases.[9] These distinctions aid in pattern recognition, particularly when visualizing temperature curves: intermittent shows sharp peaks dropping to baseline daily, continuous remains flat and high, relapsing has long gaps between spikes, saddleback exhibits a "saddle" dip between two rises, and remittent displays wavy elevations always above normal over 24-48 hours.| Fever Pattern | Key Temperature Behavior | Typical Fluctuation | Example Condition |
|---|---|---|---|
| Intermittent | Returns to normal between daily spikes | >1°C, reaches baseline | Quotidian malaria[6] |
| Continuous/Sustained | Persistently elevated with little change | <1°C | Typhoid fever[7] |
| Relapsing | Recurrent spikes after days/weeks afebrile | Variable, episodic | Borreliosis[8] |
| Saddleback/Biphasic | Two peaks with intervening partial drop | >1°C between peaks | Dengue[9] |
| Remittent | Fluctuates but stays above normal daily | >1°C, no baseline | Various infections[5] |