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edited by Mark Silverberg, MD
 
 
The Case:
A 30 year old male presents to your ED complaining of fevers and rash for the past 3 days. The fever has been fluctuating but has been as high as 103 degrees Fahrenheit. He also complains of chills, mylagias, sweats and a decreased appetite. He has a severe headache and some neck stiffness but no photophobia. He denies any further neurological complaints. This morning he noticed many “small bumps” on his chest, back and arms. He has no known medical problems, but readily admits that he has not seen a physician in 10 years. He does not remember having chicken pox as a child but thinks that he may have had it when he was a baby.
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With the exception of a fever to 102.8o F, the patient’s vital signs are normal. Upon physical examination, you see a well nourished adult who looks mildly uncomfortable. He has some minor neck stiffness, but Kernig’s and Brudzinski’s signs are not present. There is a 3-4mm eschar on his right chest, near his shoulder (left image). It is not tender to palpation. He has axillary lymphadenopathy on that side as well. On his arms, back and chest, he has a few small, red, papulovesicular lesions (right).

When questioned about the eschar, the patient states that he first noticed it 1-2 weeks ago and thought it was an insect bite, although he does not remember being bitten there and it did not itch.
 
Discussion:
The differential diagnosis for fever with a rash is large. The good emergency physician always starts out thinking of the worst possible etiology of the constellation of symptoms seen. Our patient has a fever, a rash and perhaps some mild meningeal signs; could he have meningococcal meningitis? A diagnosis of meningococcus requires prompt administration of IV antibiotics and steroids. A lumbar puncture would be necessary as well. Patients with meningococcus typically look “very sick.” Our patient looks uncomfortable, but is not ill appearing. The rash of meningococcus is typically petechial in nature although maculopapular lesions can occur. Our patient, however, has vesicular lesions, which are not usually seen in meningococcemia. It does not sound like this is the correct etiology of our patient’s symptoms but we need to be very careful excluding this diagnosis from our differential. If we are not 100% positive that our patient does not have meningococcemia, we will need to perform a spinal tap to rule it out.

Our patient has a black eschar on his shoulder. Cutaneous anthrax is probably the most common disease to present in this fashion. Do we believe that our patient has cutaneous anthrax? We need to question the patient more to see if he has any possible exposure to the anthrax bacillus. He works as an office clerk. He has not had any exposure to sheep, goats or cattle or their wool or hides. Revisiting our patient’s rash and symptoms, they are not really consistent with cutaneous anthrax. Lacking any additional history of travel abroad and no potential exposure to the bacillus, cutaneus anthrax is an unlikely diagnosis.

Fever, eschar and rash can also be the presentation of Mediterranean spotted fever. The timeline of eschar formation followed by systemic symptoms and a generalized rash certainly fits the clinical picture in our patient. Caused by Rickettsia conori, humans get infected via the bite of the dog tick (Rhipicephalus sanguineus). Mediterranean spotted fever is rare in the United States but is prevalent in Southern Europe, North Africa and the Middle East. Additionally, the rash of Mediterranean spotted fever is maculopapular and does not vesiculate.  Our patient has no recent travel history, making Mediterranean spotted fever very unlikely.

Chickenpox or varicella might also be considered in this differential diagnosis. Fever and vesicular rash certainly could be caused by the varicella virus. The rash seen with chickenpox traditionally starts on the face and trunk and spreads peripherally. Varicella lesions progress through stages of papule, vesicle, pustule, rupture and crust. The vesicles appear on top of an erythematous base earning this disease entity the classic text book description of “dew on a rose petal.” The rash appears in crops, therefore patients often have lesions in all 4 stages at any given time. Before the advent of the varicella vaccine in 1995, chickenpox was a common childhood illness with 80-90% of all varicella cases seen in those younger than 14 years of age. With the advent of this vaccine, fewer and fewer children are being diagnosed with this disease each year.
 
Infection with varicella typically confers lifelong immunity to reinfection. Could our patient be suffering from a second bout of varicella if he did indeed have it as a baby? This would be very rare; it is more likely that he would be having an adult onset first attack (though this would be rare as well). A few elements of the history and physical examination point us away from chickenpox; our patient has an eschar which is not seen in chickenpox, all of the lesions on our patient appeared at the same time and all appear to have the same morphology and the lesions are papulovesicular and do not have the red base “dew on a rose petal” appearance.

Yet another disease entity that often presents with eschar, fever and rash is rickettsialpox. Our patient developed an eschar followed by a fever and other systemic symptoms. In addition to these systems, he now has a sparse but generalized rash which is vesiculopapular in nature. First described in 1946 among residents in the Kew Gardens neighborhood in the borough of Queens, New York City, rickettsialpox is caused by Rickettsia akari. The house mouse mite (Liponyssoides sanguineus) is the vector, transmitting the bacteria amongst house mice and between the two species. Typically rickettsialpox is seen in large metropolitan areas of the northeastern United States with a large number of cases being seen in New York City. Rickettsialpox has also been seen in Arizona, Utah, Korea and the Ukraine.

The mite bite is painless and goes unnoticed most of the time. R. akari proliferates in the skin causing a firm, red papule (1-1.5 cm) with surrounding erythema which appears 7-10 days later. The papule will vesiculate and subsequently form an eschar. The primary lesion can occur anywhere on the body; covered areas are not excluded. Tenderness and pruritus are not usually seen with the initial lesion.

Another 3-7 days later, systemic symptoms abruptly manifest themselves. These typically include high fever, sweats, sore throat, rigors, mylagias (especially backaches), headache, photophobia and anorexia. One often also sees regional lymphadenopathy near the eschar. Occasionally a generalized lymphadenopathy is found.

Typically, within 2-3 days of systemic symptoms, multiple macules, papules and papulovesicles develop. The lesions usually number between 20 and 40 and are seen on the face, trunk and extremities. Lesions have been seen on the tongue, buccal mucosa and pharynx. The palms and soles may be affected as well. This disease entity seems to form the best fit to his constellation of symptoms. It looks like this will be our patient’s diagnosis.

Laboratory studies are fairly nonspecific. Leukopenia is commonly seen early in the disease. A differential will often show a relative lymphocytosis. CSF findings are typically normal. The diagnosis of rickettsialpox is typically confirmed by a four-fold rise in convalescent titers against R. akari which our patient ended up having.
Should our patient be worried? Probably not since it is a self-limited disease, but antibiotics do hasten recovery. Tetracyclines work well against R. akari. The usual course of therapy is doxycylcine 100mg orally twice a day for 5-7 days.

Diagnosis: Rickettsialpox

 

Comments   

# M.D. in EDwilliam murphy 2008-11-19 13:52
I had a case of RMSF infestion about a month ago that was missed by PMd for 4-5 days.
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