INFECTIOUS MONONUCLEOSIS

Infectious Mononucleosis (IM), commonly known as “mono” or the “kissing disease,” is a viral infection primarily caused by the Epstein-Barr virus (EBV), a member of the herpesvirus family. It is characterized by fever, sore throat, lymphadenopathy, and fatigue. The disease is common among adolescents and young adults but can affect individuals of any age. Etiology and Transmission • Causative Agent: Epstein-Barr virus (EBV), a double-stranded DNA virus. • Transmission: • Saliva (most common) – kissing, sharing drinks, utensils, toothbrushes. • Blood transfusions or organ transplantation (rare). • Respiratory secretions (less common). • EBV remains latent in B cells and can reactivate. Pathophysiology 1. Viral Entry: EBV infects the oropharyngeal epithelium and B lymphocytes via the CD21 receptor. 2. B-cell Activation: Infected B cells proliferate and produce heterophile antibodies. 3. T-cell Response: Cytotoxic T cells (CD8+) attack infected B cells, leading to lymphadenopathy and hepatosplenomegaly. 4. Latency: The virus remains in memory B cells and can reactivate under immunosuppression. Clinical Features • Incubation Period: 4-6 weeks • Prodromal Phase: Fatigue, malaise, headache • Classical Triad (Hallmark Features): 1. Fever – Low to high grade, lasting 1-2 weeks 2. Pharyngitis – Severe sore throat, exudative tonsillitis (resembles streptococcal pharyngitis) 3. Lymphadenopathy – Bilateral, posterior cervical lymph nodes • Other Symptoms: • Splenomegaly (50% cases) – Risk of rupture • Hepatomegaly and mild transaminitis • Skin rash – Especially after ampicillin or amoxicillin use • Fatigue – Can persist for weeks to months Diagnosis 1. Heterophile Antibody Test (Monospot Test) • Detects antibodies that agglutinate horse/sheep RBCs • Positive in 85% of cases, usually after the first week 2. EBV-Specific Serology • Viral Capsid Antigen (VCA)-IgM: Acute infection • VCA-IgG: Past or current infection • EBV Nuclear Antigen (EBNA-IgG): Past infection (appears late) 3. Peripheral Blood Smear • Atypical lymphocytes (Downey cells) – Activated cytotoxic T cells 4. Liver Function Tests (LFTs) • Mild elevated transaminases (ALT, AST) 5. Throat Culture • To rule out streptococcal pharyngitis Differential Diagnosis • Streptococcal Pharyngitis – Rapid strep test, throat culture • Cytomegalovirus (CMV) Infection – No heterophile antibodies • HIV Acute Retroviral Syndrome – ELISA or PCR • Toxoplasmosis – IgM serology for Toxoplasma gondii Management and Treatment Supportive Care (self-limiting disease, resolves in 2-4 weeks) • Rest – Avoid strenuous activities • Hydration & Nutrition • Antipyretics & Analgesics – Acetaminophen, NSAIDs • Corticosteroids – Only in severe cases (airway obstruction, severe thrombocytopenia) Avoid • Ampicillin or Amoxicillin – Causes a maculopapular rash • Contact Sports – Splenomegaly increases the risk of splenic rupture Complications • Splenic Rupture – Rare but life-threatening • Hematologic – Hemolytic anemia, thrombocytopenia • Neurologic – Guillain-Barré syndrome, encephalitis, meningitis • Chronic Fatigue Syndrome – Prolonged fatigue for months • Malignancies (EBV-associated) – Burkitt lymphoma, nasopharyngeal carcinoma, Hodgkin’s lymphoma Prevention and Prognosis • No Vaccine Available • Avoid Sharing Utensils/Kissing during active infection • Good Prognosis – Most recover fully within weeks, but fatigue can persist Conclusion Infectious mononucleosis is a common viral illness caused by EBV, primarily affecting young adults. It presents with fever, sore throat, and lymphadenopathy. Diagnosis is confirmed through heterophile antibody tests and EBV serology. Treatment is mainly supportive, and patients should avoid contact sports to prevent splenic rupture. Though usually self-limiting, complications can occur, particularly in immunocompromised individuals.