Avoiding a Rash Diagnosis

A CLINICAL PROBLEM-SOLVING article by Julie Reznicek from Vanderbilt University Medical Center, Nashville, Tennessee.
A 74-year-old man presented to the emergency department with confusion and lethargy. 2 weeks earlier, his wife noted a decrease in his activity level in association with an unsteady gait and multiple falls. He lived in an urban area in central Tennessee. He was active outdoors and reported feeding a stray kitten daily. On admission, the patient's temperature was 39.3°C. Multiple nonblanching, erythematous, macular lesions were present from the knees to the ankles bilaterally, sparing the soles of the feet.
The differential diagnosis for delirium in an elderly patient is broad. Patients with infectious conditions, such as pneumonia, and those with noninfectious conditions, such as myocardial infarction, may present with delirium and often have no localizing symptoms or fever. Primary neurologic processes that are consistent with this presentation include subdural hematoma, subarachnoid hemorrhage, stroke, and meningoencephalitis. Given his outdoor activities, tickborne diseases and arboviruses need to be considered.
The patient was admitted to the medical intensive care unit, and empirical treatment was begun for bacterial meningitis, HSV encephalitis, and rickettsial infections. He remained febrile, and his level of consciousness declined during the next 6 hours.