Tuberculosis is caused by tubercle bacillus and pathologically characterized by the formation of tuberculous granuloma(tubercle).Lung is the commonest site for tuberculosis. Pulmonary tuberculosis(TB) is classified into primary and secondary TB. Primary complex is the feature of primary TB. Most secondary TB represents reactivation of old primary infection. These lesions are nearly always located in lung apices, sometimes bilaterally. Subtypes of secondary tuberculosis includes focal TB,infiltrative TB,chronic fibrocavitive TB,caseous pneumonia, tuberculoma and tuberculosis pleurisy. Miliary TB may be a consequence of either primary or secondary TB in which there is severe impairment of host resistance. The disease becomes widely disseminated, resulting in numerous small granulomas in many organs. Lesions are commonly found in the lungs, meninges,kidneys,bone marrow and liver, but no organs is exempt. Intestinal tuberculosis,tuberculous peritonitis and meningitis,tuberculosis of kidney、fallopian tubes and epididymis, tuberculous osteomyetitis,and vertebral tuberculosis(Pott disease) are common in extrapulmonary tuberculosis.
The term typhoid fever has been applied when the causative organism is Salmonellosis typhi.Human is the only host of S.typhi,which is shed in the feces,urine,vomitus,and oral secretions by acutely ill persons and in the feces by chronic carriers without overt disease.Therefore,typhoid fever is a disease largely of developing countries where sanitary conditions are sufficient to stop its spread.Fever with a remittent pattern,relative bradycardia,hepatomegaly and splenomegaly, rose spots and decreased numbers of neutrophils and eosinophils are clinical characteristics of the illness.S.typhi causes proliferation of monocyte-macrophage system resulting in the formation of typhoid nodules(typhoid granuloma) which are composed of macrophages containing bacteria,red blood cells(erythrophagocytosis),and nuclear debris(typhoid cell).Intermingled with the phagocytes are lymphocytes and plasma cells. Peyer patches in the terminal ileum become sharply delineated,plateau-like elevations up to 8cm in diameter,with enlargement of draining mesenteric lymph nodes.In the second week,the mucosa over swollen lymphoid tissue is shed,resulting in oval ulcers with their long axes in the direction of bowel flow.Intestinal hemorrhage and perforation may occur as the most serious complications in this periond.In the antibiotic era,it is difficult to find typical four stages(swollen,necrotic,ulcerative and healing stages).Typical granulomas can also been found in the spleen,liver ,born marrow and lymph nodes.Gallblader colonization,which may be associated with gallstones,causes a chronic carrier state.
Dysentery refers to diarrhea with abdominal cramping and tenesmus in which loose stools contain blood,pus,and mucus.Bacillary dysentery is caused by Shigella dysenteriae,Shigella flexneri,Shigella boydii ,and Shegella sonnei as well as certain O type enterotoxic E.coli.(Amebic dysentery is caused by the protozoan parasite Entamoeba histolytica).In typical bacillary dysentery,a fibrinosuppurative exudates first patchily,then diffusely covers the mucosa and produces a dirty gray to yellow pseudomembrane.The inflammatory reaction within the intestinal mucosa builds up,the mucosa becomes soft and friable, and irregular superficial ulcerations appear.On histologic examination,there is a predominantly mononuclear leukocytic infiltrate within the lamina propria, but the surfaces of the ulcers are covered with acute,suppurativee,neutrophilic reaction accompanied by congestion,marked edema,fibrin deposition,and thromboses of small vessels.As the disease progresses, the ulcer margins are transformed into active granulation tissue.When the disease remits,this granulation tissue fills the defect, and the ulers heal by regeneration of the mucosal epithelium,sometimes with the formation of polyps.
Diseases transmitted during sexual contact are sexually transmitted diseases(STD),but none of STD is acquired solely via coitus.The STDs are largely diseases of life-style,and their incidence is higher among patients with multiple sexual partners.As a consequence,the coexistence of many STDs is prevalent in groups with high levels of sexual activity.Patients with an STD should be considered at increased risk for infection with human immunodeficiency virus(HIV) and should be offered antibody testing.In China,common sexually transmitted microbial pasthogens are now human papillomavirus(HPV)(condyloma acuminatum),HIV(AIDS),Neisseria gonorrhoeae(gonorrhea) and Treponema pallidum(syphilis).
Neisseria gonorrhoeae(syn.gonococcus) causes acute suppurative inflammation of the urethra and periurethral glands,which may also extend to the prostate and epididymis.About 90% of males develop a purulent urethral discharge with pain on passing urine as a result of infection, in contrast to females in whom about 70% of gonococcal infections are asymptomatic.Gonorrhoea is a common infection,mainly occurring in young adults,and has a high infectivity.Genital warts caused by HPV(6,11) are increasing in prevalence and are now probably the most commonest type of lesion seen in patients attending departments of genito-urinary medicine.In the male,the characteristic lesion is hyperplastic,fleshy wart or condyloma acuminatum.This wart occurs most commonly on the glans penis and inner lining of the prepuce or in the terminal urethra. Less often,lesions develop on the shaft of the penis,the perianal region or the scrotum.Histologically,the epidermis shows papillomatous hyperplasia.Many of the epidermal cells show cytoplasmic vaculation(koilocytes),a feature indicating a viral aetiology.Viral DNA can be identified by in situ hybridization,PCR and in situ PCR.Viral proteins may be detected by immunohistochemistry.Syphilis caused by a spirochaete(Treponema pallidum) is now a less prevalent sexually transmitted infection.The primary chancre usually develops on penis.It forms a painless indurated nodule which soon becomes an ulcer with rounded margins.Initially,the tissue response consists of edema with necrosis and an associated exudates of fibrin and polymorphs.At a later stage there is an endarteeritis with perivascular infiltrate of lympnocytes and plasma cells.Thrombotic occlusion of these vessels produces necrosis and ulceration of the epidermis. There is usually an associated unilateral or builateral inguinal lymphadenitis. Without treatment the primary chancre heals in a few weeks, leaving an atrophic scar. Secondary syphilis develops within two years of the primary lesion and may include condylomata lata and generalized lymphadenitis in many cases. The tertiary stage of syphilis may involve the formation of a gumma in the testis, but is also associated with thoracic aortic aneurysms and central nervous system changes. The term AIDS(acquired immunodeficiency syndrome) was defined by the Centers for Disease Control(CDC) to describe patients who lacked other causes for impaired immunity and who developed unusual malignancies such as Kaposi’s sarcoma or opportunistic infections. AIDS is characterized by a profound defect in cell-mediated immunity, with lymphopenia and diminished T-lymphocyte responses.HIV(retrovirus) is responsible for this syndrome and found in many body fluids including blood, semen, saliva, vaginal secretions, and breast milk.Tt is trophic for T-cell lymphocytes and other cells that possess CD4 surface receptors, including macrophages, promyelocytes,intestinal immunuocytes, astrocytes, oligodendrocytes, epidermal Langerhans cells,and certain fibroblasts.The manifestations of HIV infection are a consequence of the immune defects that result from dysregulation and destruction of T helper cells(CD4 lymphocytes) and other target cells.Morphologic manifestations of impaired immunity,opportunistic infections(especially mixed) and rare sarcomas are three major categories of lesions in AIDS.