A nurse is assessing a 16-year-old adolescent who presents with fever, sore throat, and fatigue for the past week. Which assessment finding would be most characteristic of infectious mononucleosis?

Infectious mononucleosis (IM), most commonly caused by the Epstein-Barr virus (EBV), is a condition frequently tested on the NCLEX-RN. The classic clinical presentation in adolescents and young adults centers on a triad of symptoms. The provided case report confirms that IM "typically presents with fever, pharyngitis, and lymphadenopathy" ^[1]. While fatigue and sore throat are prominent, the most characteristic assessment finding that distinguishes IM from other common infections is the pattern of lymph node involvement and associated organomegaly.

Option 1 describes enlarged lymph nodes in the neck and axilla with splenomegaly. This aligns perfectly with the pathophysiology of EBV infection. The virus infects B lymphocytes and epithelial cells, triggering a robust T-cell response. This immune battle leads to hyperplasia of lymphoid tissues. The posterior cervical lymph nodes are classically affected, but axillary and inguinal chains can also be involved. Splenomegaly is a hallmark finding, occurring in approximately 50% of cases, because the spleen is a major lymphatic organ actively filtering the infected lymphocytes. The case report on splenic infarction explicitly identifies IM as a "common illness in adolescents and young adults" and highlights splenomegaly as a key feature that can lead to complications ^[2]. On physical examination, you would palpate firm, tender, and symmetrically enlarged nodes, along with a potentially palpable spleen tip below the left costal margin.

To select the correct answer, it is crucial to understand why the other options are not the most characteristic for uncomplicated IM.

• Option 2 (Petechial rash): While a petechial rash on the soft palate (Forchheimer spots) can occur, a generalized petechial rash on the trunk and extremities is not a primary characteristic. This presentation is more concerning for other conditions like meningococcemia or a severe drug reaction. Notably, the research on age-dependent patterns in children emphasizes the clinical heterogeneity of EBV but does not list a diffuse petechial rash as a defining feature .


• Option 3 (Productive cough): A productive cough with thick yellow sputum is indicative of a bacterial respiratory infection, such as bronchitis or pneumonia. IM is a viral illness that may cause pharyngitis with tonsillar exudates, but it does not typically involve a productive lower respiratory tract cough. This finding would steer a clinician away from a primary diagnosis of IM.


• Option 4 (Joint pain and swelling): Polyarticular joint pain and swelling are characteristic of autoimmune or rheumatologic conditions, such as juvenile idiopathic arthritis or systemic lupus erythematosus, not IM. While arthralgias can occur in some viral syndromes, they are not a defining or most characteristic feature of EBV infection. The comparative study of clinical features in children and adults with IM focuses on fever duration and hepatic injury, not on joint manifestations .

When assessing an adolescent with suspected IM, your focused assessment should prioritize palpation of the lymph node chains, especially posterior cervical and axillary, and gentle palpation of the abdomen for splenomegaly. The study on splenic infarction as a complication underscores the critical importance of this assessment, as an enlarged spleen is fragile and at risk for rupture ^[2]. A finding of significant lymphadenopathy coupled with splenomegaly in a febrile, fatigued adolescent with a sore throat is a high-probability indicator of IM. This should prompt you to anticipate diagnostic tests, including a complete blood count (looking for lymphocytosis with atypical lymphocytes) and EBV-specific serology (positive viral capsid antigen IgM, negative EBNA IgG) as mentioned in the pediatric study . Your nursing care plan will then include monitoring for complications like airway obstruction from tonsillar hypertrophy, splenic rupture precautions (avoiding contact sports and abdominal palpation), and supportive care for the prolonged fatigue, which the adult study notes can lead to longer hospitalization .