A 20-month-old boy with fever for 23 days.

A 20-month-old boy developed fever at home. He was seen on the second day of fever by his primary care physician, who noted the patient had an exudative pharyngitis and prescribed cefdinir. A rapid strep test was negative. He continued with fever and developed a blotchy red rash over his torso that extended to his axillae and then arms on day 5. The same day, he was seen by an otolaryngologist and switched from omnicef to amoxicillin for persistent tonsillitis. His CBC demonstrated a hemoglobin of 11.4 g/dL; white blood cell count of 10,800/mcL; and platelet count of 368,000/mcL. The fever persisted and the patient’s parents reported to the primary care physician that the rash was worse with the fever; the child returned on day 7. The child was given IM ceftriaxone and admitted to the hospital near his home for further evaluation. A repeat CBC was not significantly changed. Cytomegalovirus (CMV) and Epstein-Barr virus (EBV) serologies and influenza studies were negative. Chemistries were notable for normal liver function tests, a lactate dehydrogenase (LDH) of 326 IU/L (mildly elevated) and an albumin of 2.5 g/dL. 1. Delineate the differential diagnosis of daily fever with rash in a young toddler.