Pathology
（for international students）
Zhou Ren M.D., Ph.D
Institute of Pathology & Forensic Medicine
Department of Pathology & Patho-physiology
Centre of Forensic Science & Technology Services
Zhejiang Univeristy
PARASITIC DISEASE
AMOEBIASIS
z Definition:
a human parasitosis
caused by Entamoeba histolytica.
INTESTINAL AMOEBIASIS (AMOEBIC
DYSENTERY, or AMOEBIC COLITIS)
1. Etiology and Pathogenesis
It is caused by Entamoeba histolytica excystation
cysts──→(small)
trophozoites──→ cysts
↓
(large) trophozoites
Pathogenicity
(1)Contact lysis of (large) trophozoites
(2)Mechanical damage and phagecytosis
(3)enterotoxin
(4) The effect of enterobacteria
(5)The susceptiblity of adult male and female
(6) Decreased host defense function
Morphology
z
Location: Cecum and ascending colon are
often affected at beginning.
(1)In acute stage
Grossly:
– Scattered foci of flask shaped ulceration(a
narrow neck and a broad base) surrounded
by edematous mucosa.
– Normal-looking mucosa between the ulcers
Microscopically:
– undermining ulceration (flask-shaped)
– Relative absence of inflammatory
infiltration
– Ameboid trophozoites(that often have
phagocytized red cells) in the margins
of ulcers
ulceration (flask-shaped)
(large) trophozoites
Clinicopathologic Association
z
mild cramps, which increases gradually
in severity, diarrhea, and, occasionally,
melena or sauce-like feces
(2) In chronic stage
z
z
z
Proliferation of mucosal epithelium and
formation of polyps
Proliferation of fibrous connective tissue and
scar formation made the lumen narrowed.
amoeboma : focal masses formed by
excessive proliferation of granulation tissue in
chronic amoebiasis
flask-shaped ulcer
z
(2)Chronic stage
z The
differentiation between
amoebic dysentery and
bacillary dysentery
Extraintestinal amoebiasis
z 1.
amoebic abscess of liver
A complication of amebic dysentery ,
brought about by amebic entering
colonic venules and passing by the
portal vein to the liver.
z liquefaction necrosis, not a true
abscess.
z
Macroscopically
z
z
Usually a single ‘abscess’,most often in the
upper part of the right lobe.
The lesion has a compressed fibrous capsule,
with an irregular shaggy necrotic inner wall
and the cavity contains thick paste-like
material rather than pus, often chocolatecolored or showing admixture of blood.
Microscopically
z The
contents include necrotic liver
cell debris and a varying number of
red cells.
z Trophozoites may be numerous or
scanty in the wall of the cavity
z Only a few neutrophils are present
Amoebic abscess of liver
Amoebic abscess of liver
z Complications
include rupture
and spread beyond the liver.
2).amoebic pulmonary abscess
Schistosomiasis
Etiology and transmission route
Three species:
a. Schistosoma hematobium
b. Schistosom mansoni
c. Schistosom japonicum
Oncomelania snail
Egg ─→ miracidium
─────→ cercaria ─→
schistosomulum ─→adult schistosome
Schistosom japonicum Eggs
cercaria
Basic lesions and pathogenesis
1.Penetration of the skin by cercariae caused a
transient local inflammatory reaction: Cercarial
dermatitis
Cercarial dermatitis
2. Lesions caused by adult schistosome and
their metabolic products
3. Lesions caused by eggs: the main
lesion of Schistosomiasis
(1)
Acute egg nodule (eosinophilic abscess) :
In schistosomiosis, eggs surrounded by many
eosinophils and like abscesses.
Hoeppli phenomenon
Charcot-Leyden crystal
(2) Chronic egg nodule (pseudotubercle):
In schistosomiosis, eggs surrounded by epithelioid cell,
multinuclear giant cell; eggs are often necrotic or
calcified. This structure is like that of a tubercle. It is a
granuloma.
In schistosomiosis, eggs
surrounded by many
eosinophils and like abscesses.
Hoeppli phenomenon
Charcot-Leyden crystal
z
In schistosomiosis, eggs surrounded by
epithelioid cell, multinuclear giant cell; eggs are
often necrotic or calcified. This structure is like
that of a tubercle. It is a granuloma.
z
In schistosomiosis, eggs surrounded by
epithelioid cell, multinuclear giant cell; eggs are
often necrotic or calcified. This structure is like
that of a tubercle. It is a granuloma.
Pathological changes in main organs
1. Intestine:
2. Liver: pipe stem cirrhosis
(massive fibrosis around major portal tracts)
3.Spleen: splenomegaly
4. Heterotopic Schistosomiasis
(1)lung
z (2)cerebrum
z (3)other organs
z
Briefly summary:
Infectious Diseases
EPIDEMIC CEREBROSPINAL MENIGITIS/MENIGOCOCCAL MENIGITIS
Type B Epidemic Encephalitis
Bacillary dysentery
Typhoid Fever
Sexually Transmitted Diseases
Acquired Immunodificiency Syndrome (AIDS)
Condyloma acuminatum
Syphilis
Gonorrhea
Parasitic Diseases
AMOEBIASIS
Schistosomiasis
inflammations