Mononucleosis

Question 1

General findings

Measles-like exanthem dopo 5-9 giorni dalla somministrazione💥

NB Atraumatic splenic rupture due to splenomegaly (spesso infatti si procede con splenectomia profilattica)

Answer 1

Infectious mononucleosis (IM), also called “mono” or the “kissing disease”, is an acute condition caused by the Epstein-Barr virus (EBV). The disease is highly contagious and spreads via bodily secretions, especially saliva. Infection frequently goes unnoticed in children; mainly adolescents and young adults exhibit symptoms. Symptomatic individuals typically first experience fever, malaise, and fatigue, which is later accompanied by acute pharyngitis, tonsillitis, lymphadenopathy, and/or splenomegaly lasting up to a month. IM is also sometimes associated with a measles-like exanthem, especially in individuals who are falsely diagnosed with bacterial tonsillitis and given ampicillin or amoxicillin. To avoid misdiagnosis, suspected cases are confirmed with a heterophile antibody test (monospot test), or in some cases, positive serology. Patients exhibit lymphocytosis, often with atypical T lymphocytes on a peripheral smear. IM is treated symptomatically, as it is usually self-limiting.

Although complications are rare, IM is associated with atraumatic splenic rupture due to splenomegaly and multiple malignancies (e.g., Hodgkin’s lymphoma, Burkitt lymphoma).

Question 2

Epidemiology

Answer 2

• Approx. 90–95% of adults are EBV-seropositive worldwide.

- Peak incidence of symptomatic disease: 15–24 years

Question 3

Etiology

Answer 3

• Pathogen: Epstein-Barr virus (EBV), also called human herpes virus 4 (HHV-4) (il virus della varicella invece può anche essere definito HHV-3)
• Transmission: Infectious mononucleosis is highly contagious and spreads via bodily secretions, especially saliva → “kissing disease” (Transmission can occur up to several weeks after the onset of symptoms.)

Question 4

Fisiopatologia

👓CD21!! I linfociti colpiti sono di tipo B! attenzione
Linfociti atipici allo striscio di sangue!

Linfociti T CD8 che attaccano i linfociti B infetti

Answer 4

EBV infects B lymphocytes in mucosal epithelium (e.g., oropharynx, cervix) via the CD21 receptor → infected B lymphocytes induce a humoral (B-cell) as well as a cellular (T-cell) immune response → an increased concentration of atypical lymphocytes in the bloodstream, which are CD8+ cytotoxic T cells that fight infected B lymphocytes

Question 5

Clinica

Young children are often asymptomatic.

FARINGITE-TONSILLITE-ADENOPATIA CERVICALE/DIFFFUSA (ddx con fase acuta HIV infection)

Answer 5

• Incubation period: 4–8 weeks💥
• Symptoms typically occur in adolescents and young adults and last for 2–4 weeks.
• Splenomegaly (50% of cases), fever, fatigue, malaise
• Pharyngitis and/or tonsillitis (reddened, enlarged tonsils covered in pus); palatal petechiae
• Bilateral cervical lymphadenopathy (especially posterior) that may become generalized and can, in severe cases, lead to airway obstruction
• Abdominal pain
• Possibly hepatomegaly and jaundice (EPATITE)

✔Maculopapular rash (similar to measles): caused by the infection itself in about 5% of cases, but is generally associated with the administration of aminopenicillin (e.g., ampicillin or amoxicillin) (The rate of aminopenicillin-related exanthem is very high (roughly around 50%) and is assumed to be due to antibodies against aminopenicillins. It is not caused by an allergic drug reaction. Non è una reazione allergica al farmaco!!)

Question 6

Diagnosis

Answer 6

1. Monospot test: detects heterophile antibodies produced in response to EBV infection using RBCs from horses; specificity of ∼ 100%, sensitivity of 85%
2. Laboratory analysis: elevated LDH and liver transaminases
3. Peripheral smear: lymphocytosis with > 10% atypical lymphocytes (in some cases, up to 90%) 💥 ( Despite being activated T cells, atypical lymphocytes strongly resemble monocytes in terms of their appearance, hence the name infectious mononucleosis.)

Serology: indicated if IM is suspected but a monospot test is negative
-Anti-viral capsid antigen antibodies (anti-VCA)
-Anti-VCA IgM: appears early and vanishes ∼ 3
months after infection
-Anti-VCA IgG: appears after 2–4 weeks and persists
for life

Question 7

Histopathology of lymph nodes

Answer 7

1. Reactive follicular hyperplasia due to increased activation of B lymphocytes
2. Paracortical expansion through numerous, large immunoblasts (B and T cells), later expanding throughout the entire node
3. Atypical Reed-Sternberg-like cells may be observed, which is why the disease is sometimes mistaken for Hodgkin’s disease.

Question 8

Treatment

Answer 8

✔Symptomatic therapy

1. Avoid physical activity that may trigger splenic rupture (e.g., contact sports) for at least 3 weeks after the onset of symptoms.
2. Fluids (IV administration if necessary)
3. Analgesics/antipyretics (e.g., acetaminophen)

Question 9

Complications

Answer 9

• Guillame-Barrè
• linfoma di Burkitt
• splenic rupture