Exam 1, hemolymphatic

Question 1

What are the 5 causes for small lymph nodes

Answer 1

developmental disorders
lack of antigenic stimulation
cachexia/malnutrition
aging/senile atrophy
viral infections (active destruction)

Question 2

Developmental disorders

Answer 2

immunodeficiency syndromes…. SCID (severe combined immunodeficiency)

Question 3

Lack of antigenic stimulation

Answer 3

specific pathogen-free animals (even lack normal flora), since there are no pathogens the lymph nodes don’t develop

Question 4

Cachexia/malnutrition

Answer 4

mainly decreases production of T lymphocytes

Question 5

Aging/senile atrophy

Answer 5

generalized depression of immune system leads to loss of lymphocytes which leads to lymph node atrophy

Question 6

Viral infections

Answer 6

• active destruction of lymphoid tissue
• BVDV–> necrosis of peyer’s patches
• canine distemper virus

Question 7

What are the 3 main processes of lymphadenopathy

Answer 7

• lymphoid hyperplasia
• lymphadenitis
• neoplasia

Question 8

Lymphoid hyperplasia morphology

Answer 8

• mottled appearance on cut surface
• retention of cortical and medullary architecture
• usually painful on palpation

Question 9

Lymphadenitis morphology

Answer 9

• typically regional lymph node drainage
• suppurative
• caseous
• granulomatous

Question 10

Neoplasia morphology

Answer 10

• homogeneous white/tan cut surface
• loss of normal architecture
• non-painful on palpation

Question 11

Local vs Generalized lymphadenopathy and a Ddx for each

Answer 11

Local: draining regional area of inflammation- Streptococcus equi (strangles)
Generalized: systemic inflammatory disease/infection- lymphoma

Question 12

What are the main causes of lymphadenitis and the type of inflammation associated with each

Answer 12

• Streptococcus- suppurative
• Corynebacterium psuedotuberculosis- caseous
• Histoplasma capsulatum, Leishmania, Mycobacterium- granulomatous

Question 13

Pathogenesis of Streptococcus equi

Answer 13

bacteria colonizes nasal mucosa –> mucopurulent rhinitis –> lymphadenitis –> swell –> abcess –> possible complications including bastard strangle

Question 14

Pathogenesis of Corynebactrium pseudotuberculosis

Answer 14

bacteria enter skin via wound –> drain to regional lymph nodes and form abscess –> fibrous capsule encloses abscess –> repeated cycles (lamination) –> caseous lymphadenitis

Question 15

Features that diff lymphoma from hyperplasia and lymphadenitis

Answer 15

• lymphoma arises from tissue outside the bone marrow
• there is no retention of normal architecture
• lymphadenitis is regional while lymphoma is generalized/systemic

Question 16

What is the viral cause of lymphoma in

• cats
• cattle

Answer 16

• FeLV

- bovine leukemia virus

Question 17

How does lymphoma cause hypercalcemia in dogs

Answer 17

neoplastic lymphocytes secrete PTHrP (parathyroid hormone related peptide), it causes the release of Ca from it’s stores thus increasing serum levels

Question 18

What is the significance of siderotic plaques in the spleen

Answer 18

• these are incidental findings
• common in older dogs
• healing of previous subcapsular hemorrhage

Question 19

What are the characteristic features of splenic torsion

Answer 19

• usually occurs on the gastrosplenic axis
• usually in combination with gastric torsion in deep-chested dogs b/c of the gastrosplenic ligament’s length and looseness
• congestion and infarction
• in dogs and pigs

Question 20

Pathogenesis of splenic torsion

Answer 20

• gastrosplenic ligament leads to torsion of the stomach as well as the spleen
• venous outflow is more impaired than arterial supply (blood can get in but it can’t get out) –> congestion –> infarction and/or rupture

Question 21

What are 2 causes of splenic infarction

Answer 21

• thromboembolism

- systemic bacterial/viral infection

Question 22

Acute vs Chronic splenic infartction

Answer 22

• acute- may have section of normal looking spleen with large, congested looking sections of spleen
• chronic- is usually subcapsular

Question 23

What are the 4 general mechanisms that cause small spleens

Answer 23

• developmental disorders
• cachexia/malnutrition
• aging/senile atrophy
• splenic contraction

Question 24

What are the 2 general mechnisms that produce uniform splenomegaly

Answer 24

Congestion

Cellular infiltration

Question 25

Splenic congestion, 2 Ddx

Answer 25

- barbiturates (anesthesia, sedation, euthanasia) | - acute septicemia (Bacillus anthracis)

Question 26

Splenic cellular infiltration, 2 Ddx

Answer 26

- macrophage hyperplasia (hemolytic anemia) | - neoplasia (lymphoma or leukemia)

Question 27

What are the top 3 Ddx for splenic nodules in dogs How do you distinguish them What is the prognosis

Answer 27

- Nodular hyperplasia- histology b/c it can look like neoplasia- benign - Hematoma- differentiate from hemangiosarcoma via histology, should only be blood- benign - Hemangiosarcoma- look at junction b/t normal spleen and bad looking areas, will see more than blood- MALIGNANT, poor prognosis

Question 28

What is the most common splenic neoplasm in the cat

Answer 28

mast cell tumor

Question 29

What spp have hemal nodes and what is the significance

Answer 29

Ruminants | - normal finding, look like lymph nodes but sinuses are blood filled, no lymphocytes

Question 30

What causes equine combined immunodeficiency (SCID)?

Answer 30

it is an autosomal recessive mutation in (often Arabian) foals that results in a failure of T and B cell production in the thymus

Question 31

What are the resulting gross lesions in the thymus for SCID? | In other secondary lymphoid organs?

Answer 31

- thymic hypoplasia | - small lymph nodes and spleen

Question 32

What are the general causes of thymic atrophy

Answer 32

- infectious agents, esp. viruses - toxins - chemotherapeutic drugs - ionizing radiation - malnutrition/cachexia - aging

Question 33

What are the 2 most common neoplasms of the thymus

Answer 33

- thymoma (benign, space occupying, in dogs is assoc with myasthenia gravis, megaesophagus) - thymic lymphoma (space occupying in mediastinum, t-cell lymphoma, cats and cattle)

Question 34

Extravascular hemolytic anemia

Answer 34

- RBCs are phagocytosed by macrophages, primarily in the spleen - senescent/damaged RBCs - binding of Ig (mechanism for IMHA)

Question 35

Intravascular hemolytic anemia

Answer 35

- RBC contents released into blood - hemoglobinemia - hemoglobinuria

Question 36

What is the pathogenesis of IMHA | How does it result in diffuse splenomegaly

Answer 36

- Ig binds to RBC surface antigen - RBC phagocytosed by splenic macrophages - proliferation of splenic macrophages - diffusely enlarged, meaty spleen - mostly in dogs

Question 37

What is the pathogenesis of neonatal isoerythrolysis | What spp is most commonly affected

Answer 37

- foal inherits blood type from sire that is incompatible with mare - mare is sensitized to foal RBC antigens in utero - foal ingests anti-RBC antibodies in colostrum - hemolysis, icterus, hemoglobinuria, splenomegaly - horse

Question 38

What is the cause of anemia in Equine Infectious Anemia

Answer 38

equine infectious anemia virus (lentivirus) is transmitted by arthropods, more common in marshy areas (use Coggins test to test for it)

Question 39

What is the pathogenesis of Equine Infectious Anemia

Answer 39

- anti-viral antibodies fix compliment on RBC membrane and virus - opsonization - phagocytosis by macrophages (extravascular hemolysis) - IMHA