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Systemic Path > Bone Marrow 2 > Flashcards

Bone Marrow 2 Flashcards

1
Q

How does the thymus develop as an animal ages?

A

The thymus is at its maximal mass at birth and regresses (involutes) with age

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2
Q

Why is the thymus considered a “composite” organ?

A

Because it contains both lymphoid and epithelial tissues

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3
Q

What does the lymphoid component of the thymus do?

A

It matures T-cells (few T-cells survive this process since the thymus is picky)

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4
Q

What does the epithelial component of the thymus do?

A

It supports the development of T-cells

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5
Q

What two diseases can a deficiency of the thymus result in?

A

Immunodeficiency or autoimmunity

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6
Q

What are the disorders of a “too-small” thymus (three)?

A
  • Severe Combined Immunodeficiency Disorder (SCID) (lymphocytes never populated the thymus to begin with)
  • Involution (increased loss)
  • Lymphoid atrophy (increased loss)
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7
Q

What are the disorders of a “too-large” thymus?

A

Neoplasia (thymoma or lymphoma)

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8
Q

What is Severe Combined Immunodeficiency Disorder (SCID)?

A

A genetic defect in the common lymphoid stem cell line leading to defective cell-mediated and humoral immune responses

(I think basically this is where you don’t make functional T-cells and B-cells, therefore your adaptive immune response is garbage)

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9
Q

Which animals can get SCID?

A

Dogs, mice, humans, and horses

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10
Q

What horse breeds commonly get SCID?

A

Arabian horses

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11
Q

What are the classic necropsy findings in SCID?

A

Bronchopneumonia in combination with an extremely small thymus, lymph nodes, and spleen

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12
Q

What does thymic atrophy result in?

A

An acquired immunodeficiency

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13
Q

Which viruses can cause thymic atrophy in dogs, cats, cows, and horses?

A

Dogs: Parvovirus and distemper virus

Cats: Panleukopenia virus

Cows: BVDV

Horses: EHV-1 in aborted foals

Thymic atrophy in puppies and kittens should steer you towards parvovirus or panleukopenia

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14
Q

What are four non-viral causes of thymic atrophy?

A
  • Malnutrition*
  • Toxins
  • Chemotherapeutic agents
  • Stress
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15
Q

What are the main differences between thymic lymphoma and thymomas?

A

Thymic lymphoma

  • Tumour composed of malignant T-cells
  • Aggressive, seen in younger animals
  • More often seen in cats and cows (cows is associated with sporadic form, not BLV. In cats it’s more FeLV associated)

Thymoma

  • Tumour derived from the epithelial components
  • Uncommon
  • Occurs in older animals
  • Usually benign
  • Can cause autoimmune diseases (ex. myasthenia gravis)
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16
Q

How can you differentiate between thymic lymphomas and thymomas grossly?

A

Trick question - you can’t really tell from gross examination. You need to use the signalment, clinical signs, and histopathology to differentiate

17
Q

If you are suspicious of a lymph node pathology, what should you check first?

A

You should always trace it back to the site of lymph drainage

18
Q

What are the disorders of a “too-small” lymph node (five)?

A
  • SCID
  • Aging
  • Lack of antigenic stimulus
  • Viral (BVD, CDV)
  • Cachexia and malnutrition
19
Q

What is the term for a large lymph node?

A

Lymphadenopathy or lymphadenomegaly

20
Q

What are the disorders of a “too-large” lymph node (five)?

A
  • Reactive lymphoid hyperplasia (ex. bacterial bronchopneumonia)
  • Acute lymphadenitis (ex. strangles)
  • Chronic lymphadenitis
  • Primary neoplasia (ex. lymphoma)
  • Metastatic neoplasia (ex. metastatic melanoma)
21
Q

How can you tell the difference between reactive lymphoid hyperplasia and neoplasia?

A

With reactive lymphoid hyperplasia you should still see a distinct cortex and medulla. In neoplasia, you usually lose all distinguishing characteristics

22
Q

What are the disorders of a “too-small” spleen?

A

Blood related:

  • Contraction from excitement or shock

Lymphocyte related:

  • Cachexia
  • Aging
  • Splenic lymphoid hypoplasia (due to SCID)
23
Q

What are the disorders of a “too-large” spleen (four)?

A
  • Bloody spleen (uniform splenomegaly with blood)
  • Meaty spleen (uniform splenomegaly without blood)
  • Splenic nodules with bloody consistency
  • Splenic nodules with firm consistency
24
Q

Name three differentials for uniform splenomegaly with blood

A
  1. Congestion (due to torsion or barbiturate administration)
  2. Acute hemolytic anemia
  3. Acute hyperemia (caused by acute septicemia, ex. anthrax)
25
Q

What does uniform splenomegaly with blood look like grossly?

A

These spleens are big, dark red to blue-black, and ooze blood on section

Systemic Path (19 decks)

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