NEET MDS Lessons
General Pathology
Paget Disease (Osteitis Deformans)
This unique bone disease is characterized by repetitive episodes of exaggerated, regional osteoclastic activity (osteolytic stage), followed by exuberant bone formation (mixed osteoclastic-osteoblastic stage), and finally by exhaustion of cellular activity (osteosclerotic stage). The net effect of this process is a gain in bone mass; however, the newly formed bone is disordered and lacks strength. Paget disease usually does not occur until mid-adulthood but becomes progressively more common thereafter. The pathognomonic histologic feature is a mosaic pattern of lamellar bone (likened to a jigsaw puzzle) due to prominent cement lines that haphazardly fuse units of lamellar bone. (Fig. 12-5) The axial skeleton and proximal femur are involved in the majority of cases. In patients with extensive disease, hypervascularity of the marrow spaces can result in high-output congestive heart failure. Cranial nerves impingement also occurs and can lead to head ache and auditory disturbances. Rarely Paget disease is complicated by bone sarcoma (usually osteogenic).
Roseola
- alias exanthem subitum; caused by Herpes virus type 6.
- children 6 months to 2 years old; spring and fall; incubation 10-15 days.
- sudden onset of a high fever with absence of physical findings; febrile convulsions are particularly common.
- fever falls by crisis on the 3rd or 4th day → 48 hours after temperature returns to normal macular or maculopapular rash starting on the trunk and spreading centrifugally.
Cholangitis
Cholangitis is inflammation of the bile ducts.
1. It is usually associated with biliary duct obstruction by gallstones or carcinoma, which leads to infection with enteric organisms. This results in purulent exudation within the bile ducts and bile stasis.
2. Clinically, cholangitis presents with jaundice, fever, chills. leukocytosis, and right upper quadrant pain
Haemolytic anaemia
Anemia due to increased red cell destruction (shortened life span)
Causes:
A. Corpuscular defects:
1.Membrane defects:
- Spherocytosis.
- Elliptocytosis.
2. Haemoglobinopathies:
- Sickle cell anaemia.
- Thalassaemia
- Hb-C, HBD, HbE.
3. Enzyme defects .deficiency of:
- GIucose -6 phosphate dehydrogenase (G6-PD)
- Pyruvate kinase
4. Paroxysmal nocturnal haemoglobinuria.
B. Extracorpusular mechanisms
1. Immune based:
- Autoimmune haemolytic anaemia.
- Haemolytic disease of new born.
- Incompatible transfusion.
- Drug induced haemolysis
2. Mechanical haemolytic anaemia.
3. Miscellaneous due to :
- Drugs and chemicals.
- Infections.
- Burns.
features of haemolytic anaemia
- Evidence of increased Hb breakdown:
-> Unconjugated hyperbilirubinaemia.
-> Decreased plasma haptoglobin.
-> Increased urobilinogen and stercobilinogen.
-> Haemoglobinaemia, haemoglobinuria and haemosiderinuria if Intravascular haemolysis occurs.
- Evidence or compensatory erythroid hyperplasia:
-> Reticulocytosis and nucleated RBC in peripheral smear.
-> Polychromasia and macrocytes
-> Marrow erythroid hyperplasia
-> Skull and other bone changes.
- Evidences of damage to RBC:
-> Spherocytes and increased osmotic fragility
-> Shortened life span.
-> Fragmented RBC.
-> Heinz bodies.
Herpes zoster, or shingles
- represents reactivation of a latent varicella-zoster infection.
- virus lies dormant in sensory dorsal root ganglia and when activated involves the distribution (dermatome) of the sensory nerve with a painful vesicular eruption.
- trigeminal verve distribution → Ramsay Hunt syndrome
- may indicate the presence of advanced neoplastic disease or be a complication of chemotherapy.
Respiratory Viral Diseases
Respiratory viral infections cause acute local and systemic illnesses. The common cold, influenza, pharyngitis, laryngitis (including croup), and tracheobronchitis are common.
An acute, usually afebrile, viral infection of the respiratory tract, with inflammation in any or all airways, including the nose, paranasal sinuses, throat, larynx, and sometimes the trachea and bronchi.
Etiology and Epidemiology
Picornaviruses, especially rhinoviruses and certain echoviruses and coxsackieviruses, cause the common cold. About 30 to 50% of all colds are caused by one of the > 100 serotypes of rhinoviruses.
Symptoms and Signs
Clinical symptoms and signs are nonspecific.
After an incubation period of 24 to 72 h, onset is abrupt, with a burning sensation in the nose or throat, followed by sneezing, rhinorrhea, and malaise.
Characteristically, fever is not present, particularly with a rhinovirus or coronavirus. Pharyngitis usually develops early; laryngitis and tracheobronchitis vary by person and causative agent. Nasal secretions are watery and profuse during the first days, but become more mucoid and purulent.
Cough is usually mild but often lasts into the 2nd wk.
Erythema nodosum is the MCC of inflammation of subcutaneous fat (panniculitis).
- it may be associated with tuberculosis, leprosy, certain drugs (sulfonamides), and is commonly a harbinger of coccidioidomycosis and sarcoidosis.
- commonly presents on the lower extremities with exquisitely tender, raised erythematous plaques and nodules.
- self-limited disease.