Exam 1, hemolymphatic Flashcards
What are the 5 causes for small lymph nodes
developmental disorders lack of antigenic stimulation cachexia/malnutrition aging/senile atrophy viral infections (active destruction)
Developmental disorders
immunodeficiency syndromes…. SCID (severe combined immunodeficiency)
Lack of antigenic stimulation
specific pathogen-free animals (even lack normal flora), since there are no pathogens the lymph nodes don’t develop
Cachexia/malnutrition
mainly decreases production of T lymphocytes
Aging/senile atrophy
generalized depression of immune system leads to loss of lymphocytes which leads to lymph node atrophy
Viral infections
- active destruction of lymphoid tissue
- BVDV–> necrosis of peyer’s patches
- canine distemper virus
What are the 3 main processes of lymphadenopathy
- lymphoid hyperplasia
- lymphadenitis
- neoplasia
Lymphoid hyperplasia morphology
- mottled appearance on cut surface
- retention of cortical and medullary architecture
- usually painful on palpation
Lymphadenitis morphology
- typically regional lymph node drainage
- suppurative
- caseous
- granulomatous
Neoplasia morphology
- homogeneous white/tan cut surface
- loss of normal architecture
- non-painful on palpation
Local vs Generalized lymphadenopathy and a Ddx for each
Local: draining regional area of inflammation- Streptococcus equi (strangles)
Generalized: systemic inflammatory disease/infection- lymphoma
What are the main causes of lymphadenitis and the type of inflammation associated with each
- Streptococcus- suppurative
- Corynebacterium psuedotuberculosis- caseous
- Histoplasma capsulatum, Leishmania, Mycobacterium- granulomatous
Pathogenesis of Streptococcus equi
bacteria colonizes nasal mucosa –> mucopurulent rhinitis –> lymphadenitis –> swell –> abcess –> possible complications including bastard strangle
Pathogenesis of Corynebactrium pseudotuberculosis
bacteria enter skin via wound –> drain to regional lymph nodes and form abscess –> fibrous capsule encloses abscess –> repeated cycles (lamination) –> caseous lymphadenitis
Features that diff lymphoma from hyperplasia and lymphadenitis
- lymphoma arises from tissue outside the bone marrow
- there is no retention of normal architecture
- lymphadenitis is regional while lymphoma is generalized/systemic
What is the viral cause of lymphoma in
- cats
- cattle
- FeLV
- bovine leukemia virus
How does lymphoma cause hypercalcemia in dogs
neoplastic lymphocytes secrete PTHrP (parathyroid hormone related peptide), it causes the release of Ca from it’s stores thus increasing serum levels
What is the significance of siderotic plaques in the spleen
- these are incidental findings
- common in older dogs
- healing of previous subcapsular hemorrhage
What are the characteristic features of splenic torsion
- 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
Pathogenesis of splenic torsion
- 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
What are 2 causes of splenic infarction
- thromboembolism
- systemic bacterial/viral infection
Acute vs Chronic splenic infartction
- acute- may have section of normal looking spleen with large, congested looking sections of spleen
- chronic- is usually subcapsular
What are the 4 general mechanisms that cause small spleens
- developmental disorders
- cachexia/malnutrition
- aging/senile atrophy
- splenic contraction
What are the 2 general mechnisms that produce uniform splenomegaly
Congestion
Cellular infiltration
Splenic congestion, 2 Ddx
- barbiturates (anesthesia, sedation, euthanasia)
- acute septicemia (Bacillus anthracis)
Splenic cellular infiltration, 2 Ddx
- macrophage hyperplasia (hemolytic anemia)
- neoplasia (lymphoma or leukemia)
What are the top 3 Ddx for splenic nodules in dogs
How do you distinguish them
What is the prognosis
- 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
What is the most common splenic neoplasm in the cat
mast cell tumor
What spp have hemal nodes and what is the significance
Ruminants
- normal finding, look like lymph nodes but sinuses are blood filled, no lymphocytes
What causes equine combined immunodeficiency (SCID)?
it is an autosomal recessive mutation in (often Arabian) foals that results in a failure of T and B cell production in the thymus
What are the resulting gross lesions in the thymus for SCID?
In other secondary lymphoid organs?
- thymic hypoplasia
- small lymph nodes and spleen
What are the general causes of thymic atrophy
- infectious agents, esp. viruses
- toxins
- chemotherapeutic drugs
- ionizing radiation
- malnutrition/cachexia
- aging
What are the 2 most common neoplasms of the thymus
- thymoma (benign, space occupying, in dogs is assoc with myasthenia gravis, megaesophagus)
- thymic lymphoma (space occupying in mediastinum, t-cell lymphoma, cats and cattle)
Extravascular hemolytic anemia
- RBCs are phagocytosed by macrophages, primarily in the spleen
- senescent/damaged RBCs
- binding of Ig (mechanism for IMHA)
Intravascular hemolytic anemia
- RBC contents released into blood
- hemoglobinemia
- hemoglobinuria
What is the pathogenesis of IMHA
How does it result in diffuse splenomegaly
- Ig binds to RBC surface antigen
- RBC phagocytosed by splenic macrophages
- proliferation of splenic macrophages
- diffusely enlarged, meaty spleen
- mostly in dogs
What is the pathogenesis of neonatal isoerythrolysis
What spp is most commonly affected
- 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
What is the cause of anemia in Equine Infectious Anemia
equine infectious anemia virus (lentivirus) is transmitted by arthropods, more common in marshy areas
(use Coggins test to test for it)
What is the pathogenesis of Equine Infectious Anemia
- anti-viral antibodies fix compliment on RBC membrane and virus
- opsonization
- phagocytosis by macrophages (extravascular hemolysis)
- IMHA
