NEET MDS Lessons
General Pathology
Enterococci
Most common are E. fecalis and E. fecium. Cause inflammation at site of colonization.
Serious resistance to antibiotics. E. fecium is now a vancomycin resistant enterococcus (VRE)
Polycystic kidney disease
Characterized by the formation of cysts and partial replacement of renal parenchyma.
Genetic transmission: autosomal dominant.
Clinical manifestations:
hypertension, hematuria, palpable renal masses, and progression to renal failure. Commonly associated with berry
aneurysms.
THROMBOPHLEBITIS AND PHLEBOTHROMBOSIS
- The deep leg veins account for more than 90% of cases (DVT)
- the most important clinical predispositions are: congestive heart failure, neoplasia, pregnancy, obesity, the postoperative state, and prolonged bed rest or immobilization
- local manifestations: distal edema, cyanosis, superficial vein dilation, heat, tenderness, redness, swelling, and pain
- migratory thrombophlebitis (Trousseau sign): hypercoagulability occurs as a paraneoplastic syndrome related to tumor elaboration of procoagulant factors
Thalassaemia. Genetic based defect in synthesis of one of the normal chains.
Beta thalassaemia ---> reduced Hb A and increased HbF (α2, Y2) HBA2(α2)
Alpha thalassaemia ---> reduced Hb-A, Hb-A2 and Hb-F-with formation of Hb-H(β4) and Hb Barts (Y4).
Thalassaemia may manifest as trait or disease or with intermediate manifestation.
Features:
• Microcytic hypochromic RBC is in iron deficjency.
• Marked anisopoikilocytsis with prominent target cells.
• Reticulocytosis and nucleated RBC seen.
• Mongoloid facies and X-ray findings characteristic of marrow hyperplasia
• Decreased osmotic. fragility.
• Increased marrow iron (important difference from iron deficiency anaemia).
• Haemosiderosis, especially with repeated transfusions.
Diagnosis is by Hb electrophoresis and by Alkali denaturation test (for HbF).
Multiple myeloma.
Blood picture:
- Marked rouleaux formation.
- Normpcytic normochromic anaemia.
- There may be leucopenia or leucoery!hrohlastic reaction.
- Atypical plasma cells may be seen in some patients
- Raised ESR
- Monoclonal hypergammaglobulinaemia
- If light chains are produced in excess, they are excreted in urine as bence jones protein
Bone marrow
- Hyper cellular
- Plasma cells from at least 15 – 30% atypical forms and myeloma cells are seen.
Bronchiectasis
- Bronchiectasis is abnormal and irreversible dilatation of the bronchi and bronchioles (greater than 2 mm in diameter) secondary to inflammatory weakening of bronchial wall.
- Occur in childhood and early adult life
- Persistent cough with copious amount of foul smelling purulent sputum
Aetiopathogenesis
Bronchial wall destruction is due to:
- Endobronchial obstruction due to foreign body
- Infection due to local obstruction or impaired defence mechanism
Clinical conditions:
- Hereditary and congenital factors
- Obstruction
- Secondary complication
Hereditary and congenital factors:
- Congenital bronchiectasis due to developmental defects
- Cystic fibrosis causing defective secretion resulting in obstruction
- Hereditary immune defiency diseases
- Immotile cilia syndrome- immotile cilia of respiratory tract, sperms causing Kartagener’s syndrome (bronchiectasis, situs inversus and sinusitis) and male infertility
- Allergic bronchial asthma patients
Obstruction:
Localised variety in one part of bronchial system.
Obstruction can be due to
Foreign body
Endobronchial tumors
Hilar lymph nodes
Inflammatory scarring (TB)
Secondary complication:
Necrotizing pneumonia in Staph infection and TB
Morphologic changes
- Affects distal bronchi and bronchioles
- Lower lobes more frequently
- Lungs involved diffusely/segmentally
- Left lower lobe than right
- Pleura fibrotic & thickened adherent to chest wall
C/S lung: Honey-combed appearance
Microscopic examination:
Bronchiole-dilated
Bronchial epithelium-normal, ulcerated, squamous metaplasia
Bronchial wall-infiltration by ac & Ch inflammatory cells,
destruction of muscle, elastic tissue
Lung parenchyma-fibrosis, surrounding tissue pneumonia
Pleura-fibrotic and adherent
Autoimmune(acquired) Haemolytic anaemia
Auto antibodies are usually Ig g type (may be Ig M or Ig A). They may or may not bind complement and may be active in warm or cold temperature They may be complete (agggIutinating) or incomplete. Haemolysis s may be intravascular due to destruction of the antibody coated cells by RE system.
Causes:
a. Idiopathic
b. Secondary to
o Drugs - Methyldopa, Mefanamic acid
o Disease like
-> Infections especially viral.
-> Autoimmune disease especially SLE.
-> Lymphomas and chronic lymphatic leukaemia.
-> Tumours.
Diagnosis : is based on
• Evidences of haemolytic anaemia.
• Demonstration of antibodies
- On red cell surface by direct Coomb’s test
- In serum by indirect Coomb’s test.