Differential Diagnosis for the 15-month-old Girl
- Single most likely diagnosis
- D. Roseola infantum: This is the most likely diagnosis due to the characteristic presentation of a high fever that persists for several days, followed by the abrupt appearance of a rose-colored, blanching, maculopapular rash after the fever has resolved. The age of the patient and the description of the rash and its timing relative to the fever are classic for roseola infantum.
- Other Likely diagnoses
- A. Kawasaki disease: Although less likely, Kawasaki disease could be considered due to the presence of fever, rash, and lymphadenopathy. However, the rash in Kawasaki disease is more polymorphic, and other criteria such as conjunctival injection, changes to the lips and oral cavity, and swelling of the hands and feet are not mentioned.
- E. Drug allergy: Given that the child was recently treated with acetaminophen, a drug allergy could be considered, especially if the rash appeared after the medication was started. However, the timing and description of the rash are less typical for a drug allergy.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- A. Kawasaki disease: Despite being listed as another likely diagnosis, Kawasaki disease is included here because missing it can lead to serious cardiac complications, including coronary artery aneurysms.
- C. Scarlet fever: Although the rash description does not perfectly match scarlet fever (which typically has a sandpapery texture), the potential for severe complications if left untreated (such as rheumatic fever) warrants consideration.
- Rare diagnoses
- F. Rubella: Now rare in many areas due to vaccination, rubella (German measles) could present with a similar rash and fever, but the postauricular lymphadenopathy is more characteristic of rubella.
- G. Measles: Also rare in vaccinated populations, measles presents with a rash, fever, and the three Cs (cough, coryza, and conjunctivitis), which are not mentioned in this case.
- H. Erythema infectiosum: Caused by parvovirus B19, this condition can present with a rash and fever, but typically has a distinctive "slapped cheek" appearance in the early stages, which is not described here.
- B. Nonbullous impetigo: This is a bacterial skin infection that could cause a rash but typically presents with more localized, pus-filled lesions rather than a widespread maculopapular rash.