NEET MDS Lessons
General Pathology
SPIROCHETAL DISEASE
Syphilis
A contagious systemic disease caused by the spirochete Treponema pallidum, characterized by sequential clinical stages and by years of latency.
ACQUIRED SYPHILIS
T. pallidum is a delicate spiral organism about 0.25 µm wide and from 5 to 20 µm long, identified by characteristic morphology and motility with a darkfield microscope or fluorescent techniques
In acquired syphilis, T. pallidum enters through the mucous membranes or skin, reaches the regional lymph nodes within hours, and rapidly disseminates throughout the body. In all stages of disease, perivascular infiltration of lymphocytes, plasma cells, and, later, fibroblasts causes swelling and proliferation of the endothelium of the smaller blood vessels, leading to endarteritis obliterans.
In late syphilis, T. pallidum elicits a granulomatous-like (gummatous) reaction causing masses, ulcerations, and necrosis. Inflammation may subside despite progressive damage, especially in the cardiovascular and central nervous systems.
The CNS is invaded early in the infection. During the secondary stage of the disease, > 30% of patients have abnormal CSF and may have symptoms of meningitis
Symptoms, Signs, and Course
The incubation period of primary syphilis can vary from 1 to 13 wk but is usually from 3 to 4 wk. The disease may present at any stage and long after the initial infection
Primary stage: The primary lesion, or chancre generally evolves and heals within 4 to 8 wk in untreated patients. After inoculation, a red papule quickly erodes to form a painless ulcer with an indurated base that, when abraded, exudes a clear serum containing numerous spirochetes
The regional lymph nodes usually enlarge painlessly and are firm, discrete, and nontender. Chancres occur on the penis, anus, and rectum in men and on the vulva, cervix, and perineum in women. Chancres may also occur on the lips or the oropharyngeal or anogenital mucous membranes.
Secondary stage: Cutaneous rashes usually appear within 6 to 12 wk after infection and are most florid after 3 to 4 mo.
Frequently, generalized, nontender, firm, discrete lymphadenopathy and hepatosplenomegaly are palpable. Over 80% of patients have mucocutaneous lesions, 50% have generalized lymphadenopathy, and about 10% have lesions of the eyes (uveitis), bones (periostitis), joints, meninges, kidneys (glomerulitis), liver, and spleen.
Acute syphilitic meningitis may develop, with headache, neck stiffness, cranial nerve lesions, deafness, and, occasionally, papilledema.
Condyloma lata--hypertrophic, flattened, dull pink or gray papules at the mucocutaneous junctions and in moist areas of the skin--are extremely infectious. Hair often falls out in patches, leaving a moth-eaten appearance (alopecia areata).
Latent stage
In the early latent period (< 2 yr after infection), infectious mucocutaneous relapses may occur, but after 2 yr contagious lesions rarely develop, and the patient appears normal. About 1/3 of untreated persons develop late syphilis
Late or tertiary stage: Lesions may be clinically described as (1) benign tertiary syphilis of the skin, bone, and viscera, (2) cardiovascular syphilis, or (3) neurosyphilis.
The typical lesion is a gumma, an inflammatory mass that evolves to necrosis and fibrosis and that is frequently localized but may diffusely infiltrate an organ or tissue
Benign tertiary syphilis of the bones results in either periostitis with bone formation or osteitis with destructive lesions causing a deep, boring pain, characteristically worse at night. A lump or swelling may be palpable.
Cardiovascular syphilis: A dilated, usually fusiform aneurysm of the ascending or transverse aorta, narrowing of the coronary ostia, or aortic valvular insufficiency usually appears 10 to 25 yr after the initial infection
Neurosyphilis
In meningovascular neurosyphilis, brain involvement is signaled by headache, dizziness, poor concentration, lassitude, insomnia, neck stiffness, and blurred vision. Mental confusion, epileptiform attacks, papilledema, aphasia, and mono- or hemiplegia may also occur
Diagnosis:
Two classes of serologic tests for syphilis (STS) aid in diagnosing syphilis and other related treponemal diseases: screening, nontreponemal tests using lipoid antigens detect syphilitic reagin and include the Venereal Disease Research Laboratory (VDRL) and the rapid plasma reagin (RPR) tests. Specific treponemal tests detect antitreponemal antibodies and include fluorescent treponemal antibody absorption (FTA-ABS) test, microhemagglutination assay for antibodies to T. pallidum (MHA-TP), and Treponema pallidum hemagglutination assay (TPHA).
In darkfield microscopy, light is directed obliquely through the slide so that rays striking the spirochetes cause them to appear as bright, motile, narrow coils against a dark background
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
Acute tubular necrosis
Characterized by impaired kidney functions due to the destruction of the renal tubule epithelium.
Caused by a variety of conditions that lead to ischemia of the renal tubules, usually resulting from renal tubular injury or problems with vascular flow. It can also be induced by ingesting toxins or drug-related toxicity (e.g., gentamicin).
The most common cause of acute renal failure.
Is a reversible condition, although it can be fatal.
Congestive heart failure (CHF)
A. Left-sided CHF
1. May result from nearly any heart disease affecting the left ventricle (e.g., ischemic heart disease, hypertension, valvular disease).
2. Common signs and symptoms include:
a. Dyspnea (shortness of breath) exacerbated by exertion.
b. Paroxysmal nocturnal dyspnea.
c. Orthopnea.
d. Tachypnea.
e. Pleural effusion.
f. Consequences include pulmonary edema.
B. Right-sided CHF
1. The most common cause of right heart failure is left heart failure. It uncommonly occurs in isolation. Other causes include left-sided lesions (mitral stenosis), pulmonary hypertension, cardiomyopathy, and tricuspid or pulmonary valvular disease.
2. Frequently presents with peripheral edema, especially in the ankles and feet (i.e., dependent edema), enlarged liver or spleen, and distention of the neck veins.
Neutrophilia
Causes
-Pyogenic infections.
-Haemorrhage and trauma.
-Malignancies.
-Infarction.
-Myelo proliferative disorders.
Huntington’s disease
a. Causes dementia.
b. Genetic transmission: autosomal dominant.
c. Characterized by the degeneration of striatal neurons, affecting cortical and basal ganglia function.
d. Clinically, the disease affects both movement and cognition and is ultimately fatal.
Immunohistochemistry
This is a method is used to detect a specific antigen in the tissue in order to identify the type of disease.