Rickettsialpox is...

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Severe cases

















a mild, self-limited, zoonotic febrile illness characterized by eschar formation at the location of a mite bite, followed by systemic symptoms and a more generalized papulovesicular rash. The causative agent is Rickettsia akari, a member of the spotted-fever group of rickettsiae.

Frequency: United States...
Rickettsialpox occurs primarily in urban areas, where the density of mites, mice, and humans is high. Huebner et al first isolated and named rickettsialpox in 1946 in New York City.1 Rickettsialpox has been reported primarily in the northeastern and midwest United States. Although the prevalence of confirmed cases is very low, several reports suggest the disease is more common than previously thought. Serologic evidence of rickettsialpox exposure was found in 16% of 631 intravenous drug users in inner-city Baltimore, Md, and in 9% of 204 intravenous drug users in Harlem, NY.2,3 In addition, between 2001 and 2003, the number of clinical samples submitted to the Centers for Disease Control and Prevention (CDC) increased following the anthrax bioterror attack. Consequently, rickettsialpox is widely believed to be an underrecognized and underreported clinical entity.

Causes... 

Rickettsialpox is caused by R akari and was first described in 1946.Rickettsialpox is sporadically observed in many urban centers of the United States. The bloodsucking mite L sanguineus is the vector, and mice (typically M musculus) and other rodents are the reservoir.When murine hosts are scarce, A sanguineus will bite humans.No human-to-human transmission occurs.

Physical...

Patients may have high fever fluctuating between 101- 104oF. The maculopapulovesicular exanthema is usually comprised of 20-40 lesions but may range from 5-100. The lesions typically begin as papules with subsequent vesiculation, but may remain avesicular. Lesions are usually scattered on the face, trunk, and extremities with no particular sequence of involvement.Patients may present with lesions on the tongue, buccal mucosa, and pharynx. Lesions may also be present on palms and soles. The lesions are typically asymptomatic but can be pruritic. Rashes last a week. Scabs form but do not leave scars. At the time of presentation, an eschar is present in at least 95% of affected individuals. The mite bite is painless and begins as an erythematous papule, which develops into a tense vesicle that ruptures to form a dark crust with surrounding induration. More than one eschar may be present. Mite bites can occur on any part of the body, including the hands, feet, face, and angle of the mouth (labial commissure). They do occur in covered areas.Regional adenopathy may be present and is usually tender.






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of Rickettsialpox
Pathophysiology...
R akari is an obligate intracellular gram- negative coccobacillus. Its vector is the colorless mite Liponyssoides sanguineus (formerly Allodermanyssus sanguineus), which is found on mice (most commonly the house mouse [Mus musculus]) and other rodents. These hosts serve as the reservoir for the disease. A sanguineus will bite humans when murine hosts are scarce. About 7- 10 days after the painless bite, a papular skin lesion appears at the bite location and becomes vesicular with a surrounding area of erythema. An eschar forms and slowly heals. About 3-7 days after the initial skin lesion develops, patients may suddenly develop high-grade fever, chills, headaches, and myalgias with subsequent development of a sparse generalized papulovesicular rash. The disease is mild and self-limited and usually persists for about a week.

History...

Following a mite bite, R akari proliferates locally in the skin. After 7-10 days, a firm, red papule 1-1.5 cm in diameter appears; in a few days, it vesiculates with a surrounding area of erythema.The lesion then ulcerates,forms an eschar,and slowly heals.

About 3-7 days after the appearance of the skin lesion, rickettsialpox may manifest as a sudden onset of high fever, chills, sore throat, rigor and profuse sweating, myalgias (especially backache),anorexia,and photophobia. Untreated, fever may last a week. Vertigo, conjunctival injection, cough, rhinorrhea, nausea, and vomiting sometimes occur. Headaches and neck stiffness may be severe. Regional lymphadenopathy at the draining site of the eschar is common, and generalized lymphadenopathy has also been reported. Lymphangitis is not a feature of rickettsialpox.

Approximately 2-3 days after the onset of systemic symptoms, the generalized papulovesicular rash of rickettsialpox erupts. This can involves palms and soles and is occasionally accompanied by an oropharyngeal enanthem. This rash typically lasts a week.

Mortality/Morbidity... 

Rickettsialpox is a benign, self-limited disease. No fatalities have been reported. The incubation period varies from 10-21 days. Rickettsialpox usually resolves within 14-21 days; however, headache and lassitude may persist for another 1-2 weeks.