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Placenta

Infectious conditions

Specific infectious organisms


Reviewers: Mandolin Ziadie, M.D. (see Reviewers page)
Revised: 20 December 2011, last major update October 2011
Copyright: (c) 2003-2011, PathologyOutlines.com, Inc.

Bacteroides fragilis
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● Gram negative anaerobic bacillus that inhabits the gastrointestinal tract
● Rare cause of chorioamnionitis and premature delivery (Arch Gynecol Obstet 1990;247:1)
● Ascending infection from genitourinary tract
Micro description: gram negative bacilli
Positive stains: immunofluorescent stains used to demonstrate small, safety-pin like organisms

Candida albicans
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● Fungal organism
● Most common cause of acute chorioamnionitis with peripheral funisitis
● Most cases are diagnosed in preterm deliveries
Gross description: well-circumscribed, pale yellow plaques scattered over the surface of the umbilical cord
Micro description: microabscesses containing yeast in subamniotic layer of umbilical cord (Hum Pathol 1983;14:984); chorioamnionitis or necrotizing funisitis may be present

Chlamydia psittaci (Psittacosis)
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● Pregnant women exposed to products of conception of animals (usually sheep) infected with Chylamidia psittaci
● Usually causes flu-like illness in adults, but may be severe and progressive febrile illness during pregnancy with DIC, impaired renal function, heachache and abnormal liver enzymes
Micro description: intense acute intervillositis, perivillous fibrin deposition with villous necrosis and large irregular basophilic intracytoplasmic inclusions within syncytiotrophoblast (Mod Pathol 1997;10:602)

Chlamydia trachomatis
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● Obligate intracellular bacterial causing genitourinary infections including chorioamnionitis, endometritis and salpingitis
● Usually associated with preterm delivery, fetal conjunctivitis and less commonly with pneumonia

Cytomegalovirus
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● DNA virus that causes 10% of chronic villitis cases; often no clinical symptoms (Hum Pathol 1994;25:815)
● Fetal CMV infection is most severe in placentas with plasmacytic villitis and inclusion bodies (Arch Pathol Lab Med 1984;108:403)
Gross description: placenta may be large and edematous or small and fibrotic
Micro description: lymphocytic or plasmacytic villitis with hyalinized villi and mineralization; Hofbauer cell (fetal macrophage) hyperplasia, rare intranuclear and cytoplasmic inclusions (Arch Pathol Lab Med 1992;116:21)
● Immunohistochemistry helpful since histology often non-specific (Hum Pathol 1992;23:1234)

Micro images:



Intranuclear inclusions


Congenital cytomegalovirus (CMV) infection

Coccidiodomyosis
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● Probably not spread transplacentally
● Neonatal disease probably due to transpartum or postpartum aspiration (Arch Pathol Lab Med 1981;105:347, Arch Pathol Lab Med 1978;102:512)

Cryptococcus
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Case reports: mother taking steroids for systemic lupus erythematosus (Arch Pathol Lab Med 1994;118:757), HIV+ mother with massive pulmonary embolus and disseminated infection; yeast cells in perivillous space (Hum Pathol 1989;20:920)
Gross description: white parenchymal nodules
Micro description: intervillous and villous encapsulated budding yeasts; increased fetal macrophages; no chorioamnionitis or villitis

Fusobacterium
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● Gram negative anaerobic bacteria associated with periodontal disease, preterm birth and stillbirth
Micro description: acute chorioamnionitis; meshworks of pleomorphic and filamentous bacteria that are difficult to detect with routine stains; use Warthin-Starry, Giemsa or Brown and Hopps stains

Haemophilius influenzae
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● Gram negative bacteria that causes antepartum and post-partum sepsis, premature delivery, neonatal meningitis and stillbirth
Micro description: acute chorioamnionitis and umbilical vasculitis with short gram-negative bacilli, highlighted by Brown and Hopps stain

Herpes simplex virus (HSV)
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● Rare, may be accompanied by necrotizing funisitis (HSV2) (Hum Pathol 1994;25:715)
Micro description: chorioamnionitis and villous changes that range from bland villous necrosis to mild lymphocytic villitis, active chronic villitis and intervillositis with necrosis
-Characteristic viral inclusions, villous fibrosis and calcification are present
-Immunohistochemistry should be performed in suspicious cases without inclusions
Molecular description: HSV infection of decidua capsularis (Arch Pathol Lab Med 1991;115:1141)
DD of necrotizing funisitis: syphilis

Human immunodifficiency virus (HIV)
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● Viral particles / antigens identified in placental Hofbauer cells, endothelium and trophoblasts by electron microscopy, immunohistochemistry and PCR (Hum Pathol 1992;23:411)
● No specific histopathology; inflammatory findings due to secondary infection

Human papillomavirus (HPV)
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● More common in spontaneous abortion specimens than elective abortion specimens
● Usually infects syncytiotrophoblasts (Hum Pathol 1998;29:170)

Listeria
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● Gram positive bacteria strongly associated with stillbirth, premature delivery and sepsis
Gross description: small white nodules (microabcesses) scattered throughout parenchyma
Micro description: acute intervillositis with intervillous microabcesses; organisms identified with gram stain

Micro images:



Placental villitis with a small microabscess in congenital infection


Malaria
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Micro description: active disease shows free and intra-erythrocytic parasites in intervillous space with minimal amounts of coarse brown pigment
-Chronic intervillositis with trophoblast basement membrane thickening and increased syncytial knots has been noted
-In chronic infections, parasites coexist with pigment covered with fibrin
-In inactive infections, only pigment is identified
● 50% with parasites in placenta had no parasites in peripheral blood
Additional references: Am J Surg Pathol 1998;22:1006, Hum Pathol 2001;32:1022, Hum Pathol 2000;31:85

Measles
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Case reports: monozygotic twins with maternal infection
-One twin died in utero; placenta showed massive fibrin deposition, residual trophoblasts had measles inclusion bodies but fetal organs were negative for measles virus; surviving twin had focal intervillous fibrin deposits and a few measles positive syncytiotrophoblasts, but no evidence of measles after 7 months (Mod Pathol 2001;14:1300)

Gross images:



Marked subchorionic, intervillous and decidual fibrin deposition


Micro images:



Histology of the placenta of the stillbirth

EM images:



Ultrastructural findings


Mycobacterium tuberculosis
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Micro description: miliary tubercles in villi or perivillous fibrin with granulomatous or chronic deciduitis

Mycoplasma and Ureaplasma
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● Role of Ureaplasma urealyticum or Mycoplasma hominis is controversial but these organisms, often associated with bacterial vaginosis, are believed to play an important role in chorioamnionitis and possibly perinatal morbidity, including preterm delivery

Parvovirus B19
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● Destroys early RBCs (normoblasts), causing anemia and resultant fetal hydrops with marked erythroid hypoplasia of bone marrow and occasional giant erythroblasts
● Fetuses may also develop myocarditis
Micro description: increased fetal erythroblasts with intranuclear inclusions and villous edema

Syphilis (Treponema pallidum)
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● Often associated with stillbirth or early neonatal death
● Umbilical cord often normal; 36% have necrotizing funisitis
Micro description: immature, edematous villi with increased fetal erythroblasts, endarteritis and perivasculitis of stem vessels and lymphoplasmacytic villitis
-Necrotizing funisitis or acute villitis have also been reported
-May not have prominent plasma cells (Hum Pathol 1996;27:366, Hum Pathol 1993;24:779); associated with intravillous hemosiderin
-Most cases with positive PCR have negative histology, so do PCR of placental tissue if suspect syphilis
Positive stains: visualize spirochetes in cord using silver (Warthin-Starry or Steiner) stain and immunofluorescent stains (Hum Pathol 1995;26:784)

Toxoplasma
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Micro description: low grade chronic villitis and villous fibrosis with Hofbauer cell hyperplasia and endarteritis
-Chronic intervillositis may be present
-Cysts and free organisms are identified in the chorionic plate or amnion

Varicella zoster virus
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● Early infections (before 20 weeks) may result in fetal eye, skin, limb and neural developmental abnormalities
● Later infections may result in neonatal varicella
Case reports: spontaneous abortion in first trimester (Hum Pathol 1998;29:94)
Micro description: early infection associated with acute necrotizing villitis; later infection presents with lymphocytic villitis with giant cells and stromal fibrosis
-Characteristic viral inclusions, villous fibrosis and calcification are present
-Immunohistochemistry should be performed
Additional references: Hum Pathol 1996;27:191

End of Placenta > Infectious conditions > Specific infectious organisms


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