Chapter 8 final part

Question 1

Features of tertiary syphilis

Answer 1

• occurs in 1/3 of untreated patients after 5+ years
• syphilitic aortitis:progressive dilatation of aortic root and arch with valvular insufficiency and proximal aortic aneurysm (caused by endarteritis of the vasa vasorum)
• neurosyphilis: e.g. tabes dorsalis, general paresis, or can be asymptomatic
• benign tertiary syphilis: gummas form in bone, skin and mucus membranes as a result of delayed hypersensitivity; rare, seen mainly in AIDS patients now

Question 2

Congenital syphilis

Answer 2

• transplacental transmission, most often during primary or secondary syphilis
• early: snuffles, desquamative rash
• late/tardive:syphilitis osteochondritis and periostitis with saddle nose and saber shins; fibrosis of liver and lungs
• classic triad of late congenital syphilis: eight nerve deafness, interstitial keratisis and Hutchinson teeth

Question 3

Transmission of Borrelia burgdorferi

Answer 3

-transmitted from rodents to humans via Ixodes ticks

Question 4

Stage 1 of lyme disease

Answer 4

-erythema chronicum migrans: erythematous skin lesion at the bite site, usually recovers in 4-12 weeks, sometimes accompanied by fever

Question 5

Stage 2 (early disseminated) lyme disease

Answer 5

-spirochetes spread hematogenously and cause secondary skin lesions, migratory arthralgias, lymphadenopathy, cardiac arrhythmias (myocarditis and pericarditis) and meningitis

Question 6

Stage 3 lyme disease

Answer 6

• chronic, debilitating arthritis

- mild to severe encephalitis and polyneuropathy

Question 7

Pathogenesis of lyme disease

Answer 7

-mostly secondary to the immune response

Question 8

Morphology of skin lesions in lyme disease

Answer 8

-edema and lymphoplasmacytic infiltrate

Question 9

Clostridium perfringens

Answer 9

• release collagenase and hyaluronidase to break down ECM and tissues
• secrete 14 different toxins, including alpha toxin which degrades cell membranes and causes nerve sheath damage

Question 10

C botulinum, C tetani

Answer 10

• release neurotoxins that cause paralysis
• botulinum toxin blocks vesicle fusion at the neuromuscular junction preventing neurotransmission, resulting in flaccid paralysis; respiratory paralysis causes death

Question 11

C difficile

Answer 11

-releases toxin A that stimulates chemokine production, and toxin B that causes cytopathic effects (cytotoxin)

Question 12

Features of ricketttsial infections

Answer 12

• cause typhus, rocky mountain spotted fever
• primarily infect vascular endothelial cells
• manifestations of disease primarily due to vascular leakage

Question 13

Major cause of death in rocky mountain spotted fever

Answer 13

-non-cardiogenic pulmonary edema causing ARDS

Question 14

What are pseudohyphae

Answer 14

-buds fail to detach producing elongated chains, as in candida albicans

Question 15

Four types of mycoses

Answer 15

1) cutaneous/superficial (dermatophytes)
2) subcutaneous: involve skin and subcutis with rare systemic dissemintation
3) endemic: dimorphic fungi that cause serious disease in healthy individuals
4) opportunistic: life threatening illness in immunocompromised individuals

Question 16

Cryptococcus

Answer 16

• meningoencephalitis in healthy people and opportunistic infections
• inhaled; present in soil and bird droppings
• 5-10 micron yeasts with a thick gelatinous capsule that is mucicarmine and PAS positive

Question 17

Aspergillus

Answer 17

• airborne conidia, inhaled, which germinate into hyphae that invade tissues
• neutrophils are a major defense against aspergillus such that neutropenia is a risk factor for invasive aspergillosis
• aspergilloma: colonizing fungus in lung cavities with minimal or no tissue invasion
• invasive aspergillosis: immunosuppressed hosts, primarily in the lung but wide hematogenous spread with a tendency for angioinvasion
• 5-10 micron thick septate hyphae with acute angle branching (40 degrees)

Question 18

Life cycle of malaria

Answer 18

• sporozoite, the infectious stage, is present in female Anopheles mosquito salivary glands that invade liver cells upon injection into human
• replicated rapidly in hepatocytes and release merozoites with rupture of the hepatocyte
• merozoites bind to red cells and hydrolyze hemoglobin
• in the red cell, goes from trophozoite to schizont which release two merozoites

Question 19

Host resistance to malaria

Answer 19

• hemoglobin mutations such as HbC and sickle cell trait

- immune responses including antibodies and specific T cells

Question 20

Leishmania

Answer 20

• obligate intracellular parasite
• promastigote develops and lives in the sandfly vector and amastigote multiples intracellularly in host macrophages
• four types of infection: cutaneous, visceral, mucocutaneous and diffuse cutaneous
• parasites stain with Giemsa

Question 21

Chagas disease

Answer 21

• Trypanosoma cruzi, intracellular protozoan
• lethal acute myocarditis with amastigotes causing myocyte swelling
• chronic chagas: dilated, large heart (dilated cardiomyopathy), often with conduction defects and mural thrombi that may embolize

Question 22

Taenia solium (cystercercosis)

Answer 22

• scolex (head) with suckers and hooklets and flat segments (proglottids) that contain reproductive organs
• if eggs are ingested, the larvae hatch and penetrate the gut wall, causing hematogenous dissemination and encyst in organs including the brain resulting in convulsions and other neurologic features

Question 23

Echinoccocus granulosus (hydatid disease)

Answer 23

-ingested, hatch in the duodenum and invade liver, lungs and bone

Question 24

Schistosomiasis

Answer 24

• transmitted by freshwater snails
• eggs carried by portal circulation to liver cause prominent inflammatory reactions and eventual cirrhosis
• S hematobium: inflammatory cystitis