NEET MDS Lessons
General Pathology
Other lung diseases
1.Sarcoidosis
1. Sarcoidosis
a. More common in African-Americans.
b. Associated with the presence of noncaseating granulomas.
Sarcoidosis is an immune system disorder characterised by non-necrotising granulomas (small inflammatory nodules). Virtually any organ can be affected, however, granulomas most often appear in the lungs or the lymph nodes.
Signs and symptoms
- Sarcoidosis is a systemic disease that can affect any organ. Common symptoms are vague, such as fatigue unchanged by sleep, lack of energy, aches and pains, dry eyes, blurry vision, shortness of breath, a dry hacking cough or skin lesions. The cutaneous symptoms are protean, and range from rashes and noduli (small bumps) to erythema nodosum or lupus pernio
- Renal, liver, heart or brain involvement may cause further symptoms and altered functioning. Manifestations in the eye include uveitis and retinal inflammation
- Sarcoidosis affecting the brain or nerves is known as neurosarcoidosis.
- Hypercalcemia (high calcium levels) and its symptoms may be the result of excessive vitamin D production
- Sarcoidosis most often manifests as a restrictive disease of the lungs, causing a decrease in lung volume and decreased compliance (the ability to stretch). The vital capacity (full breath in, to full breath out) is decreased, and most of this air can be blown out in the first second. This means the FEV1/FVC ratio is increased from the normal of about 80%, to 90%.
Treatment
Corticosteroids, most commonly prednisone
2. Cystic fibrosis
a. Transmission: caused by a genetic mutation (nucleotide deletion) on chromosome 7, resulting in abnormal chloride channels.
b. The most common hereditary disease in Caucasians.
c. Genetic transmission: autosomal recessive.
d. Affects all exocrine glands. Organs affected include lungs, pancreas, salivary glands, and intestines. Thick secretions or mucous plugs are
seen to obstruct the pulmonary airways and intestinal tracts.
e. Is ultimately fatal.
f. Diagnostic test: sweat test—sweat contains increased amounts of chloride.
3. Atelectasis
a. Characterized by collapse of the alveoli.
b. May be caused by a deficiency of surfactant and/or hypoventilation of alveoli.
Molecular techniques
Different molecular techniques such as fluorescent in situ hybridization, Southern blot, etc... can be used to detect genetic diseases.
Systemic Candidiasis (Candidosis; Moniliasis)
Invasive infections caused by Candida sp, most often C. albicans, manifested by fungemia, endocarditis, meningitis, and/or focal lesions in liver, spleen, kidneys, bone, skin, and subcutaneous or other tissues.
Infections due to Candida sp account for about 80% of all major systemic fungal infections.
Symptoms and Signs
Esophagitis is most often manifested by dysphagia. Symptoms of respiratory tract infections are nonspecific, such as cough. Vaginal infections cause itching, burning, and discharge. Candidemia usually causes fever, but other symptoms are typically nonspecific. Sometimes, a syndrome develops resembling bacterial sepsis, with a fulminating course that may include shock, oliguria, renal shutdown, and disseminated intravascular coagulation.
Hematogenous endophthalmitis starts as white retinal plaques that can cause blindness as destructive inflammation progresses, extending to opacify the vitreous and causing potentially irreversible scarring. Most often, there are no symptoms in early stages of Candida endophthalmitis. If treatment is not begun before symptoms appear, significant or even total loss of vision is likely to occur in the affected eye. In neutropenic patients, eye involvement is more often manifested by retinal hemorrhages; papulonodular, erythematous, and vasculitic skin lesions may also develop.
Hepatic failure
Etiology. Chronic hepatic disease (e.g., chronic active hepatitis or alcoholic cirrhosis) is the most common cause of hepatic failure although acute liver disease may also be responsible.
- Widespread liver necrosis may be seen with carbon tetrachloride and acetaminophen toxicity. Widespread steatosis is seen in Reye's syndrome, a cause of acute liver failure most often seen in children with a recent history of aspirin ingestion for an unrelated viral illness.
- Massive necrosis may also be seen in acute viral hepatitis, after certain anesthetic agents, and in shock from any cause.
Clinical features. Hepatic failure causes jaundice, musty odor of breath and urine, encephalopathy, renal failure (either by simultaneous toxicity to the liver and kidneys or the hepatorerial syndrome), palmar erythema, spider angiomas, gynecomastia , testicular atrophy
Infections caused by N. meningiditis
1. Bacteremia without sepsis. Organism spreads to blood but no major reaction.
2. Meningococcemia without meningitis. Fever, headache, petechia, hypotension, disseminated intravascular coagulation. The Waterhouse-Friderichsen Syndrome is a rapid, progressive meningococcemia with shock, organ failure, adrenal necrosis, and death.
3. Meningitis with meningococcemia. Sudden onset fever, chills, headache, confusion, nuchal rigidity. This occurs rapidly.
4. Meningoencephalitis. Patients are deeply comatose.
Diagnosis made by examining CSF.
Cardiac arrhythmia
Cardiac arrhythmia is a group of conditions in which muscle contraction of the heart is irregular for any reason.
Tachycardia :A rhythm of the heart at a rate of more than 100 beats/minute , palpitation present
Causes : stress, caffeine, alcohol, hyperthyroidism or drugs
Bradycardia : slow rhythm of the heart at a rate less than 60 beats/min
Atrial Arrhythmias
- Atrial fibrillation
Atrial Dysrhythmias
- Premature atrial contraction
- Atrial flutter
- Supraventricular tachycardia
- Sick sinus syndrome
Ventricular Arrhythmias
- Ventricular fibrillation
Ventricular Dysrhythmias
- Premature ventricular contraction
- Pulseless electrical activity
- Ventricular tachycardia
- Asystole
Heart Blocks
- First degree heart block
- Second degree heart block
o Type 1 Second degree heart block a.k.a. Mobitz I or Wenckebach
o Type 2 Second degree heart block a.k.a. Mobitz II
- Third degree heart block a.k.a. complete heart block
Atrial fibrillation
Atrial fibrillation is a cardiac arrhythmia (an abnormality of heart rate or rhythm) originating in the atria.
AF is the most common cardiac arrhythmia
Signs and symptoms
Rapid and irregular heart rates
palpitations, exercise intolerance, and occasionally produce angina and congestive symptoms of shortness of breath or edema
Paroxysmal atrial fibrillation is the episodic occurence of the arrhythmia Episodes may occur with sleep or with exercise
Diagnosis:
Electrocardiogram
- absence of P waves
- unorganized electrical activity in their place
- irregularity of R-R interval due to irregular conduction of impulses to the ventricles
Causes:
- Arterial hypertension
- Mitral valve disease (e.g. due to rheumatic heart disease or mitral valve prolapse)
- Heart surgery
- Coronary heart disease
- Excessive alcohol consumption ("binge drinking" or "holiday heart")
- Hyperthyroidism
- Hyperstimulation of the vagus nerve, usually by having large meals
Treatment
Rate control by
Beta blockers (e.g. metoprolol)
Digoxin
Calcium channel blockers (e.g. verapamil)
Rhythm control
Electrical cardioverion by application of a DC electrical shock
Chemical cardioversion is performed with drugs eg amiodarone
Radiofrequency ablation : uses radiofrequency energy to destroy abnormal electrical pathways in heart tissue It is used in recurrent AF
In confirmed AF, anticoagulant treatment is a crucial way to prevent stroke
Atrial flutter
Atrial flutter is a regular, rhythmic tachycardia originating in the atria. The rate in the atria is over 220 beats/minute, and typically about 300 beats/minute
he morphology on the surface EKG is typically a sawtooth pattern.
The ventricles do not beat as fast as the atria in atrial flutter
Supraventricular tachycardia
apid rhythm of the heart in which the origin of the electrical signal is either the atria or the AV node
it is important to determine whether a wide-complex tachycardia is an SVT or a ventricular tachycardia, since they are treated differently
Sick sinus syndrome : a group of abnormal heartbeats (arrhythmias) presumably caused by a malfunction of the sinus node, the heart's "natural" pacemaker.
Ventricular fibrillation
is a cardiac condition which consists of a lack of coordination of the contraction of the muscle tissue of the large chambers of the heart. The ventricular muscle twitches randomly, rather than contracting in unison, and so the ventricles fail to pump blood into the arteries and into systemic circulation.
Ventricular fibrillation is a medical emergency: if the arrhythmia continues for more than a few seconds, blood circulation will cease, as evidenced by lack of pulse, blood pressure and respiration, and death will occur. Ventricular fibrillation is a cause of cardiac arrest and sudden cardiac death
Blood-Lymphatic Pathology
Disorders of primary hemostasis
1. General characteristics of disorders of primary hemostasis (due to problems of blood vessels or platelets):
a. Occur early in life.
b. Unlike secondary hemostasis, bleeding occurs in more superficial areas such as skin and mucous membranes rather than in secondary hemostasis.
c. Signs include petechiae.
d. Can be caused by vascular and platelet abnormalities or alterations in the plasma proteins required for adhesion of platelets to vascular subendothelium.
e. Laboratory findings include prolonged bleeding time, as seen in platelet disorders.
2. Vascular abnormalities
Scurvy
(1) Caused by a vitamin C deficiency leading to decreased synthesis of collagen. Note: vitamin C is necessary for the formation of collagen via hydroxylation of lysine and proline.
(2) Symptoms include:
- Delayed wound healing.
- Petechiae and ecchymosis.
- Gingival bleeding, swelling, and ulcerations.
3. Platelet abnormalities
a. Thrombocytopenia
(1) Characterized by a decreased number of platelets.
(2) The most common type of bleeding disorder.
(3) Can be caused by a number of diseases, such as irradiation, acute leukemia, disseminated intravascular coagulation (DIC), or idiopathic thrombocytopenic purpura (ITP).
b. Thrombocytopenic purpura
(1) Idiopathic: An autoimmune disease characterized by the presence of autoantibodies against platelets, resulting in the removal of platelets by splenic macrophages.
(2) May also be drug-induced.
Disorders of secondary hemostasis
1. General characteristics of disorders of secondary hemostasis (due to problems with clotting factors):
a. Symptoms occur later in life.
b. As compared to disorders of primary hemostasis, bleeding occurs in deeper areas and larger vessels (i.e., joint spaces).
c. Laboratory findings include abnormal:
- Partial thromboplastin time (PTT)—measures the intrinsic and common clotting pathway (i.e., tests all coagulation factors except factor 7).
- Prothrombin time (PT)—measures the extrinsic pathway.
- Does not affect the bleeding time.
Hemophilia
a. Caused by a deficiency of particular clotting factor(s).
b. All types of hemophilia affect the intrinsic pathway of the clotting cascade.
c. Signs and symptoms include:
- Prolonged PTT.
- Continuous bleeding from cuts or trauma, which can lead to excessive blood loss.
- Bleeding into joint cavities (hemarthroses) and muscle.
Two types:
(1) Hemophilia A (classic hemophilia)
- Caused by a deficiency of factor 8 (antihemophilic factor).
- Transmission: sex-linked recessive—only occurs in males; however, females can be carriers.
(2) Hemophilia B (Christmas disease)
- Caused by a deficiency of factor 9 (plasma thromboplastin).
- Transmission: sex-linked recessive—only occurs in males; however, females can be carriers.
- Lower incidence rate than hemophilia A.
(3). Vitamin K deficiency
- Causes include malnutrition and malabsorption of fats.
- A decrease in clotting factors 2, 7, 9, and 10 and prothrombin is observed.
- Prolonged PT.
Disorders of both primary and secondary hemostasis
1. von Willebrand’s disease
a. Characterized by a defective von Willebrand’s factor (vWF). Defective vWF affects both primary hemostasis by affecting platelet adhesion to
endothelium, and secondary hemostasis, by a defective factor 8.
b. Genetic transmission: autosomal dominant.
It is the most common hereditary bleeding disorder.
2. Liver disease—disease of the liver results in a decreased production of coagulation factors and therefore can lead to problems with hemostasis.
3. Disseminated intravascular coagulation a condition in which clots form throughout the vasculature. This uses up all available clotting factors and platelets, resulting in problems with bleeding.