Infectious Mononucleosis

It is an Epstein Barr virus infection in children and young adults.

Features

-Constitutional symptoms.
-Sore throat.
-Lymphnode enlargement.
-Skin rashes
-Jaundice.
-Rarely pneumonia, meningitis and encephalitis.

Blood Picture

- Total count of I0,000. 20,000 /cu.mm.
- Lymphocytosis (50-90%) with atypical forms. They are larger with more cytoplasm which may be vacuolated or basophilic. Nucleus may be indented. with nucleoli (Downy type I to III).
- Platelets may be reduced.
- Paul Bunell test (for heterophil antibody against sheep RBC) is positive
 

N. meningiditis

Major cause of fulminant bacteremia and meningitis.  Has a unique polysaccharide capsule.  It is spread person to person by the respiratory route.  Frequently carried in nasopharynx, and carriage rates increased by close quarters.  Special risk in closed populations (college dorms) and in people lacking complement.  Sub-saharan Africa has a “meningitis belt.”

Pathogenesis is caused by adherence factors that attach to non-ciliated nasopharyngeal epithelium. These factors include pili which promote the intial epithelial (and erythrocyte) attachment, and Opa/Opc surface binding proteins.

Adherence stimulates engulfment of bacteria by epithelial cells.  Transported to basolateral surface.

The polysaccharide capsule is a major virulence factor that prevents phagocytosis and lysis. 

A lipo-oligosaccharide endotoxin also contributes to sepsis.

Pathology

The branch of medicine dealing with the essential nature of disease, especially changes in body tissues aorgans that cause or are caused by disease. Pathology is the structural and functional manifestations of disease.

Anatomic pathology  the anatomical study of changes in the function, structure, or appearance of organs or tissues,including postmortem examinations and the study of biopsy specimens.

Cellular pathology  - Cytopathology is a diagnostic technique that examines cells from various body sites to determine the cause or the nature of disease.

Clinical pathology  pathology applied to the solution of clinical problems, especially the use of laboratory 

methods inclinical diagnosis.

Comparative pathology  that which considers human disease processes in comparison with those of other 

animals.

Oral pathology  that treating of conditions causing or resulting from morbid anatomic or functional changes in thestructures of the mouth.

Surgical pathology  the pathology of disease processes that are surgically accessible for diagnosis or treatment.

Hepatitis C virus.

 It is most often mild and anicteric but occasionally severe with fulminant hepatic failure. It is caused an RNA virus, which may be transmitted parenterally (a cause of post-transfusion hepatitis); the route of transmission undetermined in 40%-50% of cases
a. 90% of blood transfusion-related hepatitis is caused by hepatitis C.
b. 50% progress to chronic disease.
c. Increased risk for hepatocellular carcinoma.

d. Incubation period: ranges from 2 to 26 weeks, but averages 8 weeks.
-  Antibody is detected by enzyme-linked immunosorbent,assay (ELISA). The incubation period is between 2 and weeks with peak onset of illness 6-8 weeks after infection 
- Most patients progress to chronic liver disease, specifically chronic persistent hepatitis or chronic active hepatitis 
- Cirrhosis is common in patients with chronic active hepatitis and occurs in 20%-25% of infected patients. HCV is also associated with hepatocellular carcinoma.

e. Treatment and prevention: α-interferon is used to treat chronic hepatitis C. There is currently no vaccine available.

1. Pyogenic liver abscesses may be caused by E. coli, Klebsiella, Streptococcus, Staphylococcus, Bacteroides, Pseudomonas, and fungi. 

Parasitic infections

1. Schistosomiasis is caused by different organisms in different parts of the world.

a. Clinical features include splenomegaly, portal hypertension, and ascites. Lesions are caused by the immune response to ova. 
2. Amebiasis is caused by Entamoeba histolytica. 
a. Clinical features include bloody diarrhea, pain, fever, jaundice, and hepatomegaly.

Drug-induced liver damage may be caused by agents that are direct hepatotoxins, such as carbon tetrachloride, acetaminophen, methotrexate, anabolic steroids, and oral contraceptive pills. 

CARCINOMA IN SITU

Epithelial malignancy which has not yet invaded even -the local confines viz basement membrane is termed as carcinoma in situ (intra epithelial neoplasia, pre-invasive cancer)

This lesion merges morphologically with severe dysplasia

Common sites for carcinoma-in-situ :

• Cervical squamous epithelium
• Oropharynx
• Bronchial epithelium.
• Breast ducts and lobules.
• Skin, in the form of Bowen's disease.
• Glans penis and vulva in the form of Erythroplasia of Queyrat