Final answer:
A 2-year-old with a characteristic rash and low-grade fever likely has Fifth disease, which is mild for children but can be dangerous for pregnant women and individuals with hemolytic disorders or compromised immune systems.
Step-by-step explanation:
The symptoms described in the case of a 2-year-old with a low-grade fever and a lacy, reticular rash on the cheeks and upper body suggest a diagnosis of Fifth disease, also known as erythema infectiosum. This condition is caused by the parvovirus B19 and is recognizable by its distinct "slapped cheek" rash, which eventually becomes lacy as it recedes, sparing the palms and soles. Fifth disease is generally mild for children but can be serious for certain populations.
Specifically, Fifth disease can be harmful to pregnant women, as it can cause severe anemia in the fetus, potentially leading to miscarriage or stillbirth. Moreover, individuals with hemolytic disorders, such as sickle cell anemia, or compromised immune systems, may experience a more severe illness.