A 15-year-old Caucasian male with a past medical history of attention-deficit/hyperactivity disorder (ADHD) presents to the hospital emergency department (ED) with a 1-week history of fever, headache, arthralgias, vomiting, and rash.
The patient states that initial symptoms all began around the same time 1 week prior to hospital presentation when he developed severe back pain throughout his entire upper and lower midline spine, followed by generalized headache and nonbloody, nonbilious vomiting. Four days prior to presentation, he began to have bilateral wrist pain that migrated to his bilateral shoulders, knees, and ankles. The pain worsened with movement and palpation, and the only alleviating factor was taking ibuprofen, which gave mild and brief pain relief. The pain was constant and described as sharp. This was followed by a flat, dark-purple rash on bilateral arms, hands, and legs that spared his chest and abdomen.
The constellation of his symptoms as well as a new onset of limping and difficulty bearing weight led to the patient’s ED visit. He did not experience neck pain, nor redness or warmth of his joints. He did not have any confusion, weakness in any of his extremities, or visual changes. He denied any chest pain, shortness of breath, or abdominal pain.
The teenager lives at home with 7 dogs and 2 cats. He had been visiting his father in Iowa who owns 1 dog and a pet rat. He recalls feeding the rat 3 weeks ago, when he was bitten on his fourth left finger. He had minimal bleeding that resolved after a few minutes. There was neither pus nor other drainage from the lesion. A small purple blister formed and resolved without intervention after 3 days. He did not have any other symptoms for the 2 weeks following the rat bite, until the back pain began.
The patient’s vital signs were normal and stable for his age, with blood pressure of 116/64 mm/Hg, pulse of 68 beats per minute, and respiratory rate of 18 breaths per minute. He was afebrile at 98.2°F 1 hour after given ibuprofen. A review of his growth chart revealed normal and symmetric growth with no recent weight changes. He was well appearing and well hydrated. He was alert and oriented to person, place, and time and had no focal neurologic deficits. Mucous membranes were moist, and his posterior oropharynx was benign. His neck was supple with no pain on range of motion and no lymphadenopathy. He had regular rate and rhythm, no murmurs, and good distal pulses. His lungs were clear with no wheezing.
The patient’s abdomen was soft, nondistended, and nontender to palpation. He had positive bowel sounds and no hepatosplenomegaly. He had 5/5 strength in all extremities. He had a 0.5-cm to 1-cm purple closed blister without drainage on his left fourth digit (Figure 1) with a nonblanching macular petechial rash on bilateral hands, forearms, anterior lower legs, and feet. No rash was present on his chest, abdomen, palms, or soles. There was no erythema nor edema surrounding the blister on his left hand.
Initial laboratory evaluation revealed a normal complete blood count with differential, electrolytes, renal function, transaminases, creatine kinase, lactic acid, and coagulation factors. The patient did have an elevated erythrocyte sedimentation rate of 89 mm/hr (normal range [NR], 0-15 mm/hr); C-reactive protein of 20.8 mg/dL (NR, <0.5 mg/dL); and procalcitonin of 0.89 ng/mL (NR, <0.15 ng/mL).
Wound culture was obtained via puncturing the blister to express fluid, and blood culture was obtained on sodium polyanethole sulfonate (SPS)-free blood culture medium. Serum Streptobacillus moniliformis polymerase chain reaction (PCR) and serum Francisella fluorescent antibodies also were collected.
The differential diagnosis for a teenager with fever, headache, arthralgias, and rash in the setting of a known animal bite is wide. This includes rabies, Rocky Mountain Spotted Fever (RMSF), ehrlichiosis, tularemia, and rat bite fever caused by either S moniliformis or Spirillum minus (Table 1).
Rabies includes initial symptoms such as fever, headache, and vomiting that make it difficult to distinguish among other illnesses. However, as rabies progresses and affects the brain and meninges, symptoms include agitation and confusion. Rabies is unique in that it causes muscle spasms in the throat when trying to swallow, which cause dysphagia, excess salivation, and hydrophobia. In animals, rabies is diagnosed with the presence of rabies virus antigen in brain tissue using the direct fluorescent antibody (DFA) test.1
In humans, diagnosis can be made by DFA test on skin biopsy from the neck; isolation of the virus from saliva; by detection of antibody in serum in unvaccinated people and cerebrospinal fluid (CSF) in all people; and by detection of viral nucleotide sequences in saliva or skin. Treatment for a patient once bitten by an animal suspected of being rabid includes rabies immunization and human rabies immune globulin (HRIG), but after symptoms have developed, neither the vaccine nor immune globulin improves prognosis.1
Rocky Mounted Spotted Fever is caused by the bacterium Rickettsia rickettsii and typically presents with fever, headache, myalgias, and a distinctive rash in the presence of a tick bite. The characteristic rash is a red petechial rash initially involving the wrists and ankles, and within hours spreading to the palms and soles and then inward to the trunk. Hyponatremia and thrombocytopenia typically accompany the illness. The gold standard for diagnosis is the indirect fluorescent antibody (IFA) serology test. Treatment is 7 to 10 days of oral doxycycline.1
Ehrlichiosis is a tick-borne infection that usually consists of headache, myalgias, and fatigue. Rash may be present but is uncommon. Diagnosis is made by serologic testing, but the organism also can be isolated in blood or CSF culture as well as via PCR assay. Treatment is oral doxycycline for 5 to 10 days.1
Tularemia is caused by the bacterium Francisella tularensis and causes fever, headache, fatigue, and a skin ulcer at point of contact with the bite site along with swollen lymph nodes near the ulcer. Diagnosis is generally via serologic testing, but PCR assay or DFA assay also may be used. Treatment is usually 7 to 10 days of intravenous (IV) gentamicin.1
Rat bite fever is caused by S moniliformis or S minus. The main presenting symptoms of rat bite fever caused by S moniliformis include fever, chills, headache, migratory polyarthralgia, rash, and absence of lymphadenopathy. In addition, S minus causes the same symptoms as S moniliformis but does include lymphadenopathy. The bacterium S moniliformis accounts for most cases of rat bite fever in the United States with S minus infections occurring primarily in Asia.1
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