Path of the LRS Flashcards
What are 1* lymphoid organs?
BM and thymus
What are 2* lymphoid organs?
LNs, spleen, MALT
What are the 3 main disease processes to affect the LRS?
- Infection
- Immune mediated
- Neoplasia
developmental disease of the thymus. What is this often assocated with?
Hypoplasia
- congenital/developmental abnormality associated with 1* imunodeficiency eg/. X-linked SCID.
- systemic viral lymphoid depletion (FeLV/FIV/CDV)
What thymic dz is most common in cats
> Feline thymic lymphoma
- assoc w/ FeLV infection
Clinical signs of Feline thymic lymphoma and useful dxx
- 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)
Tx feline thymic lymphoma?
Chemotherapy (See lymphoma lecture)
What type of virus is FeLV?
- retrovirus, immature T cells undergo malignant transformation
Which thymic dz is most common in dogs?
- Canine thymoma (more benign, neoplasia of epithelial cells)
Which breeds are pdf canine thymoma?
- GSDs and lab retrievers
Clinical signs and usefull dxx of canine thymoma?
- dyspnoea, dysphagia, thoracic effusion
> rads, US, cytology of fluid/FNAB
Tx canine thymoma?
- surgical excision ± chemo
Prog for canine thymoma?
- good if tumour not spread beyond thymic capsule (“Stage 1” thymoma)
What is canine thymoma commonly assocated with?
Paraneoplastic syndromes eg. hypercalcaemia, myasthaenia gravis
How does entry to the LN of APCs and lymphocytes differ?
- lymphocytes enter from blood via high endothelial venules, then return to blood via thoracic duct
- APCs enter vie afferent lymph
What is the function of LNs?
- 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)
Clinical signs of chylothorax?
- dyspnoea
- lymphopenia
Common causes of chylothorax?
-thoracic duct damaged, perforatied or erodded (commonly tumour)
Which neoplasms commonly metastasise via lymphatics to draining LNs?
tonsillar SCC, MCT, malignant melanoma (esp oral)
Once lymphadenopathy has been ID’d, what needs to be determined?
- local v general disease (regional or systemic, check splenic involvement)
Most common causes of lymphadenopathy
neoplasia and infection (r/o pyrexia, WBC count etc.)
How can dx of generalised lymphadenopathy be narrowed down?
> haematology - lymphopenia = viral - neutrophilia = bacterial - eosinophilia = parasitic/allergic > LN biopsy - FNA/core biopsy[trucut]/excisional
Ddx of generalised lymphadenopathy and how they may differ on histopathology?
> 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)
should mast cells ever be presentin a LN biopsy?
NO
3 most common dz of the spleen?
- trauma/rupture/haematoma
- torsion w/ GDV
- infarction (CLASSICAL SWINE FEVER)
What 2 types of tissue make up the spleen?
Red and white pulp
4 casues of diffuse splenomegaly?
> venous congestion (torsion or PB d/t barbituates)
lymphoid hyperplasia (systemic infection/inflam/immune mediated)
systemic amyloidosis
neoplasia (lymphoma/myeloma)
4 casues of nodular splenomegaly?
> nodular hyperplasia (incidental in old animals) > abscess/cyst d/t infectious agent > 1* neoplasia - lymphoma - hameangiosarcoma - haemangioma - malignant histiocytic sarcoma > 2* neoplasia - MCT
Are infectious agents that impact on the lymphoreticular system usually more benign or pathogenic?
pathogenic and often notifiable
Which viruses can have an impact of the LRS?
- malignant catarrhal fever (herpes)
- classical swine fever (pyrexia, D+, petichial haemorrhage, neuro signs, SPLENIC INFARCTS)
- FeLV/FIV/CDV/FIP
- EIA
Which bacteria can impact the LRS?
- bacillus anthracis (Anthrax)
- strep equi (Strangles)
- Corynebacteriu, pseudoTB (caseous lymphadenitis)
- Mycobacterium bovis (TB) m. avium paraTB (Johnes) = granulomatous lymphadeniits
What should be done is Anthrax is suspected on a farm? Clinical signs?
> Cattle - sudden death - haemorrhage from orifices - splenomegaly *** DO NOT PM, WILL CONTAMINATE ENVIRONMENT*** CALL APHA > pigs and horses more protracted dz
Which exotic protozoal dz can affect LRS?
- leishmaniasis
- babesiosis
- ehrlichiosis
- theileriosis
