The diagnosis of infectious mononucleosis (IM) in young adults is primarily based on clinical and laboratory findings

Clinical presentation

• Age group: IM is most frequently observed in adolescents and young adults, with a peak incidence between ages 15-24 years
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  Disease overview

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• Symptoms: Patients typically present with sore throat, significant fatigue, palatal petechiae, posterior cervical or auricular lymphadenopathy, marked axillary lymphadenopathy, or inguinal lymphadenopathy
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  Guidelines

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  Diagnosis

  Pathway

  AAFP 2004

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• Complications: Complications can include hematological issues (e.g., hemolytic anemia, thrombocytopenia), neurologic complications (e.g., Guillain-Barre syndrome, facial paralysis), splenic rupture, airway obstruction, pneumonia, and hemophagocytic lymphohistiocytosis
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Laboratory findings

• EBV infection: IM is most frequently caused by the Epstein-Barr virus (EBV), transmitted through infected saliva
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• HLA class I polymorphisms: Certain HLA class I polymorphisms may predispose patients to the development of IM upon primary EBV infection
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  Abstract

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  HLA class I polymorphisms are associated with development of infectious mononucleosis upon primary EBV infection

  PubMed

  Highly cited

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Differential diagnosis

• Lymphoma: The morphological features of EBV-infected lymphoid tissue can mimic lymphoma, necessitating careful differentiation
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  Abstract

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  Infectious mononucleosis mimicking lymphoma: distinguishing morphological and immunophenotypic features

  PubMed

  Highly cited

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• Multiple sclerosis (MS): IM in childhood and adolescence is associated with an increased risk of a subsequent MS diagnosis, independent of shared familial factors
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  Abstract

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  Association of infectious mononucleosis in childhood and adolescence with risk for a subsequent multiple sclerosis diagnosis among siblings

  PubMed

  High-impact

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Prognosis

• Recovery: Most patients achieve complete resolution within weeks, and mortality rates are low (5.3%)
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• Chronic fatigue syndrome (CFS): IM may be a risk factor for CFS in adolescents, with female gender and greater fatigue severity associated with the development of CFS
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  Abstract

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  Chronic fatigue syndrome after infectious mononucleosis in adolescents

  PubMed

  Highly cited

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In conclusion, the diagnosis of IM in young adults is based on a combination of clinical presentation and laboratory findings, with careful consideration of differential diagnoses. The prognosis is generally favorable, although complications can occur.