What is a potential reason for a school nurse to excuse an adolescent returning from a case of mononucleosis from gym class?

Excusing an adolescent returning from a case of mononucleosis from gym class primarily relates to the potential for sustaining abdominal trauma. Mononucleosis often leads to an enlargement of the spleen, a condition known as splenomegaly. The spleen plays a crucial role in filtering blood and fighting infections, but when it becomes enlarged, it is more vulnerable to injury. Physical activities, especially contact sports or even vigorous gym activities, can put the enlarged spleen at significant risk for rupture, which is a medical emergency. Therefore, the school nurse's decision to excuse the student from gym class is rooted in the necessity to protect the adolescent from potential harm during their recovery from mononucleosis.

Factors like increased energy levels, risk of dehydration, or the need for physical fitness are less relevant in this specific context, as the primary concern is the safety of the spleen and preventing complications associated with a rupture.