Path of the LRS

Question 1

What are 1* lymphoid organs?

Answer 1

BM and thymus

Question 2

What are 2* lymphoid organs?

Answer 2

LNs, spleen, MALT

Question 3

What are the 3 main disease processes to affect the LRS?

Answer 3

• Infection
• Immune mediated
• Neoplasia

Question 4

developmental disease of the thymus. What is this often assocated with?

Answer 4

Hypoplasia

• congenital/developmental abnormality associated with 1* imunodeficiency eg/. X-linked SCID.
• systemic viral lymphoid depletion (FeLV/FIV/CDV)

Question 5

What thymic dz is most common in cats

Answer 5

> Feline thymic lymphoma

- assoc w/ FeLV infection

Question 6

Clinical signs of Feline thymic lymphoma and useful dxx

Answer 6

• anorexia, wt loss
• lethargy
• dyspnoea
  > thoracic rads
• mass in anterior thorax, effusion, loss of cardiac silhouette
  > cytology of pleural fluid/FNAB
• lymphoblasts (5x normal lymphocyte size, malignant)

Question 7

Tx feline thymic lymphoma?

Answer 7

Chemotherapy (See lymphoma lecture)

Question 8

What type of virus is FeLV?

Answer 8

• retrovirus, immature T cells undergo malignant transformation

Question 9

Which thymic dz is most common in dogs?

Answer 9

• Canine thymoma (more benign, neoplasia of epithelial cells)

Question 10

Which breeds are pdf canine thymoma?

Answer 10

• GSDs and lab retrievers

Question 11

Clinical signs and usefull dxx of canine thymoma?

Answer 11

• dyspnoea, dysphagia, thoracic effusion

> rads, US, cytology of fluid/FNAB

Question 12

Tx canine thymoma?

Answer 12

• surgical excision ± chemo

Question 13

Prog for canine thymoma?

Answer 13

• good if tumour not spread beyond thymic capsule (“Stage 1” thymoma)

Question 14

What is canine thymoma commonly assocated with?

Answer 14

Paraneoplastic syndromes eg. hypercalcaemia, myasthaenia gravis

Question 15

How does entry to the LN of APCs and lymphocytes differ?

Answer 15

• lymphocytes enter from blood via high endothelial venules, then return to blood via thoracic duct
• APCs enter vie afferent lymph

Question 16

What is the function of LNs?

Answer 16

• filters for tissue fluid, preventing sytemic sprea
• trap foreign material and maximise exposure of lymphocytes to ag
• provide best environment for lmphocyte activation, proliferation and differentiation (producing effector T cells and Ab)

Question 17

Clinical signs of chylothorax?

Answer 17

• dyspnoea

- lymphopenia

Question 18

Common causes of chylothorax?

Answer 18

-thoracic duct damaged, perforatied or erodded (commonly tumour)

Question 19

Which neoplasms commonly metastasise via lymphatics to draining LNs?

Answer 19

tonsillar SCC, MCT, malignant melanoma (esp oral)

Question 20

Once lymphadenopathy has been ID’d, what needs to be determined?

Answer 20

• local v general disease (regional or systemic, check splenic involvement)

Question 21

Most common causes of lymphadenopathy

Answer 21

neoplasia and infection (r/o pyrexia, WBC count etc.)

Question 22

How can dx of generalised lymphadenopathy be narrowed down?

Answer 22

> haematology 
- lymphopenia = viral 
- neutrophilia = bacterial 
- eosinophilia = parasitic/allergic
> LN biopsy 
- FNA/core biopsy[trucut]/excisional

Question 23

Ddx of generalised lymphadenopathy and how they may differ on histopathology?

Answer 23

> reactive
- normal architecture, increased celularity
- 2* follicles w/ germinal centres
lymphadenitis
- active infection of LN, similar to reactive bUT
- pyogranulomatous areas of inflammation
= supparative eg. strangles, caseous eg. corynebacterium pseudoTB in sheep/goats, granulomatous eg. mycobac (TB bronchial/Johnes mesenteric) or funghi
1* neoplasia
- complete lack of normal architecture, abnormal lymphocytes eg. mitotic figures, lymphoblasts
2* neoplasia
- areas of normal lymphoid tissue + infiltration with neoplastic cells (focal/diffuse)

Question 24

should mast cells ever be presentin a LN biopsy?

Answer 24

NO

Question 25

3 most common dz of the spleen?

Answer 25

- trauma/rupture/haematoma - torsion w/ GDV - infarction (CLASSICAL SWINE FEVER)

Question 26

What 2 types of tissue make up the spleen?

Answer 26

Red and white pulp

Question 27

4 casues of diffuse splenomegaly?

Answer 27

> venous congestion (torsion or PB d/t barbituates) > lymphoid hyperplasia (systemic infection/inflam/immune mediated) > systemic amyloidosis > neoplasia (lymphoma/myeloma)

Question 28

4 casues of nodular splenomegaly?

Answer 28

``` > nodular hyperplasia (incidental in old animals) > abscess/cyst d/t infectious agent > 1* neoplasia - lymphoma - hameangiosarcoma - haemangioma - malignant histiocytic sarcoma > 2* neoplasia - MCT ```

Question 29

Are infectious agents that impact on the lymphoreticular system usually more benign or pathogenic?

Answer 29

pathogenic and often notifiable

Question 30

Which viruses can have an impact of the LRS?

Answer 30

- malignant catarrhal fever (herpes) - classical swine fever (pyrexia, D+, petichial haemorrhage, neuro signs, SPLENIC INFARCTS) - FeLV/FIV/CDV/FIP - EIA

Question 31

Which bacteria can impact the LRS?

Answer 31

- bacillus anthracis (Anthrax) - strep equi (Strangles) - Corynebacteriu, pseudoTB (caseous lymphadenitis) - Mycobacterium bovis (TB) m. avium paraTB (Johnes) = granulomatous lymphadeniits

Question 32

What should be done is Anthrax is suspected on a farm? Clinical signs?

Answer 32

``` > Cattle - sudden death - haemorrhage from orifices - splenomegaly *** DO NOT PM, WILL CONTAMINATE ENVIRONMENT*** CALL APHA > pigs and horses more protracted dz ```

Question 33

Which exotic protozoal dz can affect LRS?

Answer 33

- leishmaniasis - babesiosis - ehrlichiosis - theileriosis