Pediatric emergency medicine trisk 1830 1830

RMSF is caused by Rickettsia rickettsii transmitted by the bite of a tick (see Chapter 66 Rash: Bacterial and Fungal Infections/Rash: Maculopapular ) Although initially confined to the Rocky Mountain States (hence, its name), confirmed cases have been reported from all parts of the United States with varying tick vectors The primary determinants in patient outcome are early diagnosis and treatment The best outcomes are associated with the initiation of doxycycline therapy by day five of illness The rash of RMSF begins on the third or fourth day of a febrile illness as a morbilliform eruption on the extremities, most commonly the wrists and ankles Over the next days, the rash becomes generalized by spreading centrally to involve the back, chest, and abdomen Initially, the rash consists of erythematous macules that blanch on pressure; they then become more confluent and purpuric Notably, the hemorrhagic lesions predominate in the peripheral distribution, involving the palms of the hands and the soles of the feet The severity of the rash is proportional to the severity of the disease All patients with RMSF have some degree of vasculitis that is the basis for many of the associated systemic symptoms An overall toxic appearance is common Systemic signs and symptoms include fever, headache, myalgia, conjunctivitis, vomiting, seizures, myocarditis, heart failure, shock; periorbital, facial, or peripheral edema; and disseminated intravascular coagulation or purpura fulminans Diagnosis is best made by polymerase chain reaction (PCR) testing Thrombocytopenia, hyponatremia, and increased aminotransferases usually develop as the disease process progresses Doxycycline is the drug of choice for therapy in patients of all ages at a dose of mg/kg/day in two divided doses (maximum of 100 mg two times a day), intravenously or orally Ehrlichiosis Ehrlichiosis is most common during the warmer months when ticks are most prevalent Nomenclature has undergone multiple changes Currently, disease in the United States is due to three distinct obligate intracellular bacteria: Ehrlichia chaffeensis (human monocytic ehrlichiosis or HME), Anaplasma phagocytophilum agent (human granulocytic anaplasmosis or HGA), or Ehrlichia ewingii (E ewingii ehrlichiosis) Infections with any of these bacteria cause an illness very similar to RMSF Rash is a less consistent feature of ehrlichiosis but when present may be macular, morbilliform, or petechial and is more commonly seen in pediatric patients infected with E chaffeensis Unlike RMSF, rash may