-IBIS-1.5.0-
tx
immune system
mononucleosis
diagnoses
definition and etiology
definition:
An acute disease characterized by sore throat, fever, and generalized lymphadenopathy, as well as atypical lymphocytes and heterophil antibodies.
etiology:
The infectious agent is the Epstein-Barr virus, a member of the herpes group of viruses. As with other herpes viruses, a persistent carrier state follows the primary EBV illness, although antibodies are detectable for life, signifying the patient has immunity to reinfection. The virus is present for months in the oropharyngeal secretions of recovered patients, but mononucleosis is still not very contagious. The disease is usually spread by the oral-respiratory route (aka the teenage "kissing disease"). In poorer populations, infants usually get the illness and have mild or no symptoms; in higher socioeconomic groups the disease typically develops in adolescents and young adults (15-25 year olds) and leads to the typical presentation. The average incubation time is 10-14 days in children and 30-50 days in older patients.
signs and symptoms
Following the incubation time, a 3-5 day prodromal period is experienced:
Malaise.
Headache.
Myalgia.
Fatigue.
The acute phase then begins with:
Fever (may be high: up to 39-40°C).
Pharyngitis, lymphadenopathy.
Eyelid and orbital edema.
Nausea/anorexia.
Neuritis.
Splenomegaly (50% of patients), hepatomegaly (20% of patients), jaundice (<5% of patients).
Almost any organ may be involved, which can confuse the case. During or after the acute phase the patient may manifest CNS involvement resembling Guillain-Barre syndrome, Bell's palsy, meningoencephalitis, Reye's syndrome, or cerebellar ataxia. A more uncommon form of the disease, known as the typhoidal form, strikes <10% of patients and presents with fever, slight or no sore throat, and belated hematological and serologic changes.
lab findings:
(+) Heterophil agglutination test i.e. Monospot: (+) 2-3 weeks after onset of symptoms.
Overall WBC count increase (10,000-15,000), with a definite lymphocytosis and many atypical lymphocytes (>20%).
Cold-agglutinin and rheumatoid factors (IgM antibodies) are often elevated.
EBV-specific serodiagnostic tests: (+) for acute EBV infection (IgM antibody).
course and prognosis
The acute phase of infectious mononucleosis usually lasts from 1-4 weeks, although the convalescence can be prolonged for 2-3 months. Prognosis is excellent and sequelae are rare, except for the recent recognition of a Chronic Viral Fatigue Syndrome of which sub-acute EBV may play a substantial part. Death from the acute disease is very uncommon, but may follow splenic rupture, pancytopenia, acute pericarditis/myocarditis, CNS involvement, agranulocytosis or airway obstruction.
differential diagnosis
Primary CMV: usually seen in older patients.
Other causes for acute pharyngitis: Group A beta-hemolytic strepococci infection, diptheria, Vincent's angina, other organisms.
Other causes of atypical lymphocytes: rubella, hepatitis, toxoplasmosis, mumps, drug reactions.
Other lymphoproliferative disorders: Hodgkin's disease, leukemia.
footnotes