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).
CONGESTION
Congestion or hyperaemia means an increase in the content of blood in an organ. It may be :
A. Active - due to increased arterial flow to the organ with dilatation of micro vessels as in
- Inflammation.
- Increased metabolic activity.
- Neurogenic blushing.
B. Passive - due to decreased venous drainage resulting in pooling of blood. There is always an associated element of oedema.
Pulmonary edema
Pulmonary edema is swelling and/or fluid accumulation in the lungs. It leads to impaired gas exchange and may cause respiratory failure.
Signs and symptoms
Symptoms of pulmonary edema include difficulty breathing, coughing up blood, excessive sweating, anxiety and pale skin. If left untreated, it can lead to death, generally due to its main complication of acute respiratory distress syndrome.
Diagnosis
physical examination: end-inspiratory crackles during auscultation (listening to the breathing through a stethoscope) can be due to pulmonary edema. The diagnosis is confirmed on X-ray of the lungs, which shows increased vascular filling and fluid in the alveolar walls.
Low oxygen saturation and disturbed arterial blood gas readings may strengthen the diagnosis
Causes
Cardiogenic causes:
- Heart failure
- Tachy- or bradyarrhythmias
- Severe heart attack
- Hypertensive crisis
- Excess body fluids, e.g. from kidney failure
- Pericardial effusion with tamponade
Non-cardiogenic causes, or ARDS (acute respiratory distress syndrome):
- Inhalation of toxic gases
- Multiple blood transfusions
- Severe infection
- Pulmonary contusion, i.e. high-energy trauma
- Multitrauma, i.e. severe car accident
- Neurogenic, i.e. cerebrovascular accident (CVA)
- Aspiration, i.e. gastric fluid or in case of drowning
- Certain types of medication
- Upper airway obstruction
- Reexpansion, i.e. postpneumonectomy or large volume thoracentesis
- Reperfusion injury, i.e. postpulmonary thromboendartectomy or lung transplantation
- Lack of proper altitude acclimatization.
Treatment
When circulatory causes have led to pulmonary edema, treatment with loop diuretics, such as furosemide or bumetanide, is the mainstay of therapy. Secondly, one can start with noninvasive ventilation. Other useful treatments include glyceryl trinitrate, CPAP and oxygen.
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.
Eosinophilia:
Causes
-Allergic disorders.
-Parasitic infection.
-Skin diseases.
-Pulmonary eosinophilia.
-Myeloproliferative lesions and Hodgkin's disease.
Psoriasis is a chronic disorder characterized by scaly, erythematous plaques, which histologically are secondary to epidermal proliferation.
- genetic factors (HLA relationships), environmental (physical injury, infection, drugs, photosensitivity), abnormal cellular proliferation (deregulation of epidermal proliferation) and microcirculatory changes in the papillary dermis (diapedesis of neutrophils into the epidermis) are all interrelated.
- the plaques of psoriasis are characteristically well-demarcated pink or salmon colored lesions covered by a loosely-adherent silver-white scale which, when picked off, reveals pinpoint bleeding sites (Auspitz sign).
- the nail changes in psoriasis include pitting, dimpling, thickening and crumbling with a yellowish-brown discoloration of the nail plate.
- the characteristic histologic features of psoriasis include:
- hyperkeratosis
- absence of the granulosa cells (present in lichen planus).
- parakeratosis
- regular, club-shaped elongation of the rete pegs (irregular and saw toothed in lichen planus) with vessel proliferation in the papillary dermis (reason for the bleeding associated with Auspitz sign).
- characteristic subcorneal collection of neutrophils called a Munro's microabscess (diapedesis from vessels in papillary dermi).
- 7% develop HLA B27 positive psoriatic arthritis
ANAEMIA
Definition. Reduction of the hemoglobin level below the normal for the age and sex of the patient
Classification
1. Blood loss anaemia:
- Acute.
- Chronic (results in iron deficiency).
2. Deficiency anaemia:
- Iron deficiency.
- Megaloblastic anaemia-BI2 and Folic acid deficiency.
- Protein deficiency.
- Scurvy-Vitamin C deficiency.
3. Marrow dysfunction:
- Aplastic anaemia.
- Marrow infiltration.
- Liver failure.
- Renal failure.
- Collagen diseases.
4 Increased destruction (Heamolysis)
- Due to corpuscular defects.
- Due to extra corpuscular defects