HERPES ZOSTER (Shingles)

An infection with varicella-zoster virus primarily involving the dorsal root ganglia and characterized by vesicular eruption and neuralgic pain in the dermatome of the affected root ganglia.

caused by varicella-zoster virus

Symptoms and Signs

Pain along the site of the future eruption usually precedes the rash by 2 to 3 days. Characteristic crops of vesicles on an erythematous base then appear, following the cutaneous distribution of one or more adjacent dermatomes

Eruptions occur most often in the thoracic or lumbar region and are unilateral. Lesions usually continue to form for about 3 to 5 days

Geniculate zoster (Ramsay Hunt's syndrome) results from involvement of the geniculate ganglion. Pain in the ear and facial paralysis occur on the involved side. A vesicular eruption occurs in the external auditory canal, and taste may be lost in the anterior two thirds of the tongue

Wuchereria bancrofti, Brugia malayi (Filariasis)
 - the microfilaria of Wuchereria bancrofti or Brugia malayi (nematodes) are transmitted to man by the bite of infected mosquitoes (Anophele, Aedes, Culex).
 - microfilaria characteristically circulate in the bloodstream at night and enter into the lymphatics, where they mature and produce an inflammatory reaction resulting in lymphedema (elephantiasis) of the legs, scrotum, etc. 

PARASITIC DISEASES

AMEBIASIS (Entamebiasis)

Infection of the colon with Entamoeba histolytica, which is commonly asymptomatic but may produce clinical manifestations ranging from mild diarrhea to severe dysentery.

Etiology and Pathogenesis 

Amebiasis is a protozoan infection of the lower GI tract. E. histolytica exists in two forms: the trophozoite and the cyst.

Two species of Entamoeba are morphologically indistinguishable: E. histolytica is pathogenic and E. dispar harmlessly colonizes the colon. Amebas adhere to and kill colonic epithelial cells and cause dysentery with blood and mucus in the stool. Amebas also secrete proteases that degrade the extracellular matrix and permit invasion into the bowel wall and beyond. Amebas can spread via the portal circulation and cause necrotic liver abscesses.

Symptoms and Signs 

Most infected persons are asymptomatic but chronically pass cysts in stools. Symptoms that occur with tissue invasion include intermittent diarrhea and constipation, flatulence, and cramping abdominal pain. There may be tenderness over the liver and ascending colon, and the stools may contain mucus and blood.

Amebic dysentery, common in the tropics but uncommon in temperate climates, is characterized by episodes of frequent (semi)liquid stools that often contain blood, mucus, and live trophozoites.

Chronic infection commonly mimics inflammatory bowel disease and presents as intermittent nondysenteric diarrhea with abdominal pain, mucus, flatulence, and weight loss.

Metastatic disease originates in the colon and can involve any organ, but a liver abscess, usually single and in the right lobe, is the most common
 

Urinary tract infection
Most often caused by gram-negative, rod-shaped bacteria that are normal residents of the enteric tract, especially Escherichia coli.

Clinical manifestations: 

frequent urination, dysuria, pyuria (increased PMNs), hematuria, and bacteriuria.

May lead to infection of the urinary bladder (cystitis) or kidney (pyelonephritis).

HYPERPLASIA
It is the increase in the size of an organ or tissue due to increase in the number of its constituent cells. This is seen in organs made up of labile and stable cells.

Causes
I. Increased demand:
- Bone marrow in hypoxia and haemolytic states.
- Thyroid gland in puberty

2. Persistant Trauma:
- Acanthosis of the epidermis in chronic inflammations and in warts.
- Hyperplasia of oral mucosa due tooth and denture trauma.
- Mucosa at the edges of a gastric ulcer.

3. Endocrine target organ:
- Pregnancy hyperplasia of breast.
- Prostatic hyperplasia.

4. Compensatory:

Hyperplasia of kidney when the other kidney has been removed.

5. Idiopathic:
Endocrine organs like thyroid, adrenals, pituitary etc. can undergo hyperplasia with no detectable stimulus. .
 

EMBOLISM

Definition: transportation of an abnormal mass of an abnormal mass of undissolved material from one part of circulation to another. The mass transported is called embolus.

Types
I .Thrombi and clots.
2. Gas or air.
3. Fat
4.Amniotic fluid.
5.Tumour

Thromboembolism 
This is the commonest type of embolus and may be formed of the primary thrombus  or more often of propagated clot region which is loosely attached.

Emboli from venous thrombi can result In impaction in the pulmonary  arteries and result in sudden death.
Embolism from cardiac or arterial thrombi results in systemic embolism causing infraction and gangrene.

Gaseous
This occurs when gas is introduced into the circulation:
•    Accidental opening of large veins during surgery.
•    Mismanaged transfusion. .
As air is  readily absorbed into blood only  sudden introduction or large quantities of air produces effects
Caisson’s Disease  bubbling of nitrogen from the blood during sudden decompression as seen during deep sea diving.

Fat Embolism
Causes
•    Fractures especially of long bones and multiple
•    Crush injuries.

Sites of impaction:

o    Lungs.
o    Systemic: causing -
    →    petechial skin haemorrhages.
    →    Embolism to brain leading to coma and death.
    →     Conjunctival and retinal haemorrhages
    
Tumor Embolism.

Invasion of vascular channe1.s is a feature of malignant neoplasms and this leads to:
•    Metastatic deposits,
•    DlC