Infectious Diseases Lecture Notes PDF

Infectious diseases Lecture -2- Dr. Abeer Weleed Saeed C.A.B.H.S (Pathology), DipRCPATH Department of Pathology / Ninevah Medical College 2024  Leprosy (Hansen disease) Chronic cutaneous infection caused by Mycobacterium lepra...

Infectious diseases Lecture -2- Dr. Abeer Weleed Saeed C.A.B.H.S (Pathology), DipRCPATH Department of Pathology / Ninevah Medical College 2024  Leprosy (Hansen disease) Chronic cutaneous infection caused by Mycobacterium leprae and Mycobacterium lepromatosis Also called Hansen. disease Worldwide distribution due to travel and migration but endemic in tropics It affect skin and peripheral nerves because M.O grow only in the cool. area of the body  Leprosy ◻ Mycobacterium leprae is an obligate intracellular gram positive and weakly acid fast organism ◻ The incubation period is usually 3 - 5 years ( long period) ◻ Tuberculoid leprosy occurs in individuals with good cell mediated immunity; patients develop granulomatous response ◻ Lepromatous leprosy occurs in individuals with poor cell mediated immunity; do not develop a granulomatous response.  Pathogenesis of leprosy ◻ Leprae bacilli produce no exotoxin or endotoxin, ◻ The lesion is produced by: - Destructive granuloma (type IV hypersensitivity) - Interference with metabolism of Schwann cells.  Pathogenesis of leprosy ◻ Morphology: 1- Tuberculoid leprosy (Pauci-bacillary) - Granulomatous lesions closely resembling those found in tuberculosis - Because of the strong host defense, bacilli are almost never found, hence the name paucibacillary leprosy 2- Lepromatous leprosy (multibacillary) - Lepromatous lesions contain large aggregates of lipid-laden macrophages (lepra cells), often filled with masses (“globi”) of acid-fast bacilli Leprosy (Hansen's Disease) 2-Tuberculoid leprosy Lepromatous leprosy-1 In patient with high In patients with low immunity immunity Grossly: lesion consists of Grossly: lesion consists of asymmetrical anesthetic symmetrical anesthetic macule & palpable nodules with deformity & thickened nerve. ulceration, the lesions of the face lead to leonine face. Microscopic: ◻ Tuberculoid leprosy: epithelioid histiocytes surround small cutaneous nerves; Langhans giant cells may be seen but without necrosis; the infiltrate may involve the papillary dermis up to the epidermis; may destroy arrectores pilorum muscle; bacilli are usually scarce ◻ Lepromatous leprosy: macrophages (Virchow cells, lepra) are found in poorly circumscribed masses in the dermis, with few / no lymphocytes; macrophages may be distended with large groups of leprosy bacilli (globi); bacteria are present in large numbers in cutaneous nerves and in endothelium and media of small and large vessels; may invade arrectores pilorum muscle; may have subcutaneous nodules (erythema nodosum leprorum) Tuberculoid leprosy Lepromatous leprosy Lepromatous leprosy Lepromatous leprosy Spirochetes  Syphilis ◻ Caused by spirochete ( Treponema pallidum) ◻ It is a chronic venereal disease. ◻ Spirochete: it is a gram negative, coiled, unicellular spiral shaped m.o. ◻ Transmission: ◻ Syphilis is a sexually transmitted disease. ◻ Also the disease may transmit through the placenta to the fetus (transplacental transmission) Epidemiology ◻ World Health Organization (WHO) estimated 7.1 million new adult cases of syphilis worldwide in 2020 with increasing incidence in the United States (WHO: Syphilis [Accessed 22 September 2023], CDC: Sexually Transmitted Disease Surveillance 2021 [Accessed 22 September 2023]) ◻ Men who have sex with men and non-Hispanic persons are disproportionately affected (CDC: Sexually Transmitted Disease Surveillance 2021 [Accessed 22 September 2023]) ◻ Dual diagnosis with HIV is common and syphilis increases the risk of acquiring HIV as well as other sexually transmitted infections ◻ Majority of cases are transmitted through vaginal, anogenital and orogenital contact with an infectious lesion during the primary or secondary stages of the disease ◻ Rarely can be transmitted through nonsexual contact including skin to skin and blood transfusion ◻ Congenital syphilis can be acquired, at any stage, via transplacental transmission or contact with an infectious lesion during birth (N Engl J Med 2020;382:845) ◻  Stages of syphilis : 1. Primary S 2. Secondary S 3. Tertiary S  Stages of syphilis : Primary syphilis: ◻ Lesion (chancre) develops few days to 3 weeks after infection on the external genital ◻ Chancre is a solitary, slowly enlarging, painless nodule with superficial ulceration ◻ Healing occurs in 3-6 weeks either spontaneously or after treatment.  Stages of syphilis : Secondary syphilis: ◻ Usually develops 1-3 months after infection ◻ Lesions appear as : ◻ Shallow oral ulcerations ◻ Generalized skin rash ◻ Generalized lymphadenopathy ◻ Healing may occur spontaneously or after treatment.  Stages of syphilis : Tertiary syphilis: Untreated infection with Treponema pallidum can lead to tertiary syphilis years later. The most common manifestations of tertiary syphilis include aortitis (typically in the thoracic portion), neurosyphilis, and gummatous necrosis of skin, soft tissue, bone, and joint (Charcot joint). It appears several to many years after primary infection (5-30) years. Tertiary syphilis has 3 main manifestations: 1- CVS syphilis 2- CNS neurosyphilis 3- Gumma: formation firm to rubbery, multiple, nodular masses most commonly found in the liver, bones & testes. (Gumma: it is Granuloma with central coagulative necrosis)…  Syphilis Histology of syphilis: Most cases demonstrate a dense plasma cell inflammatory infiltrate on histology ◻ Proliferative endarteritis (endarteritis obliterans) affecting small vessels (endothelial hypertrophy & proliferation → intimal fibrosis) with a surrounding plasma cell infiltration are characteristic of all stages of syphilis. ◻ In Tertiary syphilis in addition to this there is gumma Secondary syphilis, in the dermis with perivascular lymphoplasmacytic infiltrate & endarteritis obliterans. Plasma cells infiltration in syphilis  Actinomyces - Caused by Actinomyces israellii - Anaerobic, gram-positive, long filamentous bacteria. - It is a commensal m.o. in the mouth, GIT, female genital tract, only occasionally they invade the tissues & produce infection - Gross: Infection produces firm masses containing numerous abscesses (honeycomb abscesses) bearing colonies as yellowish granules (sulfur granules) with sinuses & fistulae Actinomycosis Sulphur granules Microscopic (histologic) description:* ◻ Actinomyces visible as slender, filamentous, fungal-like organisms These are usually aggregated into sulfur granules ◻ Mural organisms intermixed with neutrophils, plasma cells, eosinophils and lymphocytes in a necrotic background ◻ Multinucleated giant cells and noncaseating granulomas may also be present ◻ Local lymph nodes may show reactive change  References 1. Pathology outlines. 2. References: ◻ (CDC: Mycobacterium lepromatosis Lepromatous Leprosy in US Citizen Who Traveled to Disease-Endemic Areas [Accessed 26 November 2018]) ◻ (WHO: Syphilis [Accessed 22 September 2023], CDC: Sexually Transmitted Disease Surveillance 2021 [Accessed 22 September 2023]) ◻ CDC: Sexually Transmitted Disease Surveillance 2021 [Accessed 22 September 2023]) ◻ (N Engl J Med 2020;382:845). ◻ Middle East J Dig Dis 2015;7:41, World J Gastrointest Surg 2009;1:62 actinomyces histology. Thank you