Hematology and Endocrinology

List ddx for macrocytic, normochromic, non-regenerative anemia:

• breed-related: mini and toy poodles

• dysplasia or leukemia (+/- FeLV)

• folate (+/- B12) deficiency

• PK deficiency hemolysis

List ddx for normocytic, normochromic, non-regenerative anemia:

• extramedullary dz

  • endocrinopathy (eg. hypoadrenocorticism, hypothyroidism)

  • inflam. dz

  • CKD = ↓ EPO

• aplasia (eg. estrogen)

• neoplasia (eg. acute leukemia, primary myelodysplasia)

• ineffective hematopoiesis (eg. IM, histiocytic sarcoma, drugs, infxn, eg. Ehrlichia canis)

• pure red cell aplasia

List ddx for microcytic, normochromic/hypochromic. non-regenerative anemia:

• breed-associated: Shar-Pei, Japanese breeds, Siberian Husky

• Fe deficiency

• PSVA - fxnal Fe deficiency

Medullary causes of non-regenerative anemia:

• primary medullary (eg. aplastic anemia, myelodysplastic syndromes)

• infxs

• dugs

• toxins

• neoplasia

• congenital

• immune

Extramedullary causes of non-regenerative anemia:

• renal

• endocrine

  • Addison’s

  • hypothyroidism

• GI (cobalamin deficiency)

• hepatic

• pancreatitis

• neoplasia

• Fe deficiency

Pathophysiology of PPID:

1. oxidative stress dopaminergic neurons

2. pars intermedia hyperplasia and adenoma

3. loss of inhibition

4. ↑ POMC, ACTH, glucocorticoids

Pathophysiology of EMS:

• genetic predisposition

  • easy keepers, breed

• excessive carbs

  • grain, grass

• inadequate exercise

  ↓

• insulin dyregulation

• hyperinsulinemia-associated laminitis (HAL)

Clinical signs of PPID:

• hypertrichosis

• loss of muscle mass

• abnormal sweating

• lethargy & poor performance

• chronic laminitis

• secondary infxns

• PUPD

• hyperlipidemia

Clinical signs of EMS:

• obesity or regional adiposity

• INSULIN DYSREGULATION (ID)

• HAL

• chronic low-grade inflammation

Lab findings of PPID:

• ↑ glucose

• ↑ insulin

• ↑ triglycerides

• ↑ Phos

• stress leukogram

  • ↑ neutrophils

  • ↓ lymphocytes

Lab findings of EMS:

• ↑ or normal glucose

• ↑ or normal insulin

• ↑ triglycerides

• ↓ adiponectin

Diagnostic tests for EMS:

• insulin conc.

• glucose conc.

• adiponectin conc. (↓)

• oral sugar test (OST)

Diagnostic tests for PPID:

• baseline ACTH conc.

• TRH stim. (NOT licenses by FDA in horses)

• insulin conc.

• α-MSH (research only)

• dexamethasone suppression test NOT recommended

Treatment for PPID:

• medications FOR LIFE

  • pergolide - dopamine agonist

  • cyproheptadine - serotonin antagonist

  • trilostane - 3β-HSD inhibitor

Treatment and management for EMS:

• diet

  • limit carbs and fat

  • avoid grass

  • mineral supplements

• weight loss

• exercise

• medications

  • levothyroxine - thyroid supplement

  • SGLT2 inhibitors

Why are so many horses incorrectly diagnosed and treated for hypothyroidism?

• rely solely on tT3 and tT4

• if both low:

  • seek plausible explanation

  • check fT4 conc.

  • perform TRH stim.

Signs of regenerative anemia in horses:

• NO reticulocytes

• ↑ MCV

• anisocytosis

• ↑ RDW

• hx of blood loss

• hyperplasia on BM aspirate

Signs of regenerative anemia in ruminants and camelids:

• reticulocytes

• ↑ MCV

• cows:

  • basophilic stippling

Understand why the PCV and TP does not drop immediately in cases of acute hemorrhage (<2-6 hours)

• RBC and plasma lost in equal proportions

• fluids need to re-equilibrate before ↓ PCV and TP detectable

Major LA disorders under regenerative anemia due to RBC loss:

• loss

  • external

    • GI parasites (Haemonchus, coccidia)

    • ulcerative dz

  • internal

    • thorax, peritoneum

Major categories of LA disorders under regenerative anemia due to RBC lysis:

1. infectious

2. immune-mediated

3. toxic

Major LA infectious disorders under regenerative anemia due to RBC lysis:

• parasites

  • cows:

    • babesiosis

    • Eperythroon wenyonii

• bacterial

  • cows:

    • anaplasmosis

    • leptospirosis

  • alpacas:

    • Mycoplasma haemolamae

• viral

  • horses:

    • EIA

Major LA immune-mediated disorders under regenerative anemia due to RBC lysis:

• immune-mediated

  • secondary to drugs, toxins, infxns, etc.

  • horses:

    • autoimmune

    • IMHA

      • viral (EIA)

      • bacterial (Clostridia)

      • neoplastic (lymphoma, lymphosarcoma)

      • drug (penicillin, phenylbutazone)

      • foal neonatal isoerythrolysis

Major LA toxic disorders under regenerative anemia due to RBC lysis:

• Heinz body anemia (oxidative damage, IV + EV hemolysis)

  • onion, rape, kale

  • equine: red maple leaves

  • ovine: copper toxicity

  • bovine: selenium deficiency, post-parturient hemoglobinuria

Major LA disorders under non-regenerative anemia:

• anemia of chronic disease

• BM suppression

  • lymphoma

  • other aplastic anemia

  • chemotherapy drugs

  • toxicity

• EPO deficiency

  • recombinant human EPO administration

  • CKD

• nutritional deficiency

Ddx of hypoglycemia due to decreased intake:

1. juvenile hypoglycemia

2. starvation

Ddx of hypoglycemia due to excess insulin activity:

1. beta cell neoplasia

2. insulin overdose

3. xylitol toxicity

4. extrapancreatic neoplasia

Ddx of hypoglycemia due to decreased glucose production:

1. juvenile hypoglycemia

2. severe hepatic dysfunction

3. extrapancreatic neoplasia

4. hypoadrenocorticism

Ddx of hypoglycemia due to increased utilization:

1. sepsis

2. hunting dog hypoglycemia

3. polycythemia vera or massive leukocytosis

treatments for PDH:

• surgical

  • bilateral adrenalectomy

  • hypophysectomy

• medical

  • mitotane

  • trilostane

  • radiotherapy

Signs of hypocortisolemia:

1. hyporexia

2. weakmess

3. lethargy

4. vomiting

5. diarrhea

Clinical signs associated with thrombocytopenia (<250,000 platelets/uL):

• petechiae/ecchymoses

• bleeding tendencies

Clinical signs associated with vasculitis:

• warm and painful edema

  • dependent; limbs and ventral abdomen

Clinical signs associated with coagulation disorders:

• epistaxis

• hyphema

• melena

• prolonged bleeding from venipuncture

List the 4 classifications of thrombocytopenia:

1. regenerative

2. non-regenerative

3. undetermined

4. pseudothrombocytopenia

List diagnostic tests for thrombocytopenia:

1. CBC

2. orange thiazole staining (research only)

3. platelet surface associated antibody test (flow cytometry)

4. BM biopsy

List mechanisms of regenerative thrombocytopenia and give examples:

1. increased destruction

   • immune-mediated (primary, secondary)

2. increased consumption

   • DIC, hemorrhage

3. sequestration

   • in the spleen

List mechanisms of non-regenerative thrombocytopenia and give examples:

1. decreased production

   • BM disease

     • aplastic anemia

     • myeloproliferative disease

     • neoplasia

     • drug or toxin → myelosuppression

List drugs or toxins that cause myelosuppression and thrombocytopenia:

1. bracken fern

2. furazolidone

3. mycotoxins

List mechanisms of undetermined thrombocytopenia and give examples:

1. viral infections

   • EIA

   • BVDV type II

   • EVA

2. bacterial infections

   • sepsis

   • Anaplasma phagocytophilum

3. neoplasia

Define pseudothrombocytopenia:

artificial platelet activation and agglutination outside of the body

LA diseases with clinical signs of vasculitis + petechiae/ecchymosis WITH thrombocytopenia:

• Anaplasma phagocytophilum

• endotoxemia?

  • Potomac Horse Fever

LA diseases with clinical signs of vasculitis + petechiae/ecchymosis WITHOUT thrombocytopenia:

• EVA

• purpura hemorrhagica

Anaplasma phagocytophilum clinical signs:

• vasculitis + petechia/ecchymosis

• thrombocytopenia

Anaplasma phagocytophilum dx:

• morula in neutrophils

• serology +/- PCR

Anaplasma phagocytophilum tx:

oxytetracycline

Anaplasma phagocytophilum prevention:

• tick control

• no vaccine

Purpura hemorrhagica (associated with Strangles infection) clinical signs:

• vasculitis + petechia/ecchymosis

Purpura hemorrhagica (associated with Strangles infection) dx:

• skin biopsy

  • neutrophilia

  • IF staining

Purpura hemorrhagica (associated with Strangles infection) treatment:

• immunosuppression

  • corticosteroids

  • azathioprine

• supportive therapy

Equine viral arteritis (EVA) clinical signs:

• vasculitis + petechia/ecchymosis

• leukopenia

• fever, depression, anorexia

• abortion

• rhinorrhea, epiphora, conjunctivitis, hives

Equine viral arteritis (EVA) diagnosis:

• PCR, VI, serology

• post-mortem

Equine viral arteritis (EVA) treatment:

supportive care

Equine viral arteritis (EVA) prevention:

• vaccination

• castrate males, no breeding

DIC occurs in horses secondary to:

1. sepsis

2. acute GIT disease

   • endotoxin

DIC treatment in horses:

1. treat underlying disease

2. treat endotoxemia

   • flunixin meglumine

   • polymyxin B (nephrotoxic)

   • pentoxifylline

3. replace clotting factors and anti-thrombin III by administering fresh frozen plasma

   • if blood loss, use whole blood

4. heparin therapy (controversial)

Functions of cortisol:

1. maintains arterial tone via alpha adrenergic receptors

2. maintains normal GI mucosal integrity and function

3. stimulates gluconeogenesis and glycogenesis

4. mobilizes protein and fat from tissues

5. many more!

Functions of aldosterone:

1. save sodium

2. pee potassium

3. pee H+

Protracted hyperglycemia from DM due to:

1. loss or dysfunction of insulin secretion by pancreatic beta cells

2. diminished insulin sensitivity (i.e. insulin resistance)

3. both

Insulin suspensions vs. solutions

IMHA signalment:

• dogs

  • young to middle-aged adults (2-8 years)

  • female > male

• cats

  • wide age range (1-10 years)

  • female = male

  • often with concurrent disease

List life stages involved in IMHA, regenerative or non-regenerative, and if hemolysis is observed:

• regenerative

  • mature RBCs

    • IV or EV hemolysis

• non-regenerative

  • precursor

    • NO hemolysis

  • mixed

    • +/- hemolysis

IMHA clinical signs:

• rapid onset (1-3d hx)

• anemia + systemic inflammation

  • pallor

  • lethargy, weakness

  • fever

  • GI upset (anorexia, vomiting)

  • hepatomegaly

  • peripheral lymphadenopathy

• +/- (hemolysis rate-dependent)

  • icterus

  • dark urine (bilirubinuria)

  • dark orange feces (bilirubin pigment)

  • hemoglobinuria/hemoglobinemia (rare)

• complications

  • PTE

Benefits of basal insulins:

1. mimic basal phase of endogenous insulin secretion

2. formulated as solutions so do not require resuspension

3. less within- and between-day variability in absorption

4. lower potency and longer duration

   • can be given once daily in many dogs

5. do not need to be administered around meals

6. available as pen

   • easier for owners to administer

IMHA dx:

• blood smear and CBC

  • severe ↓ PCV/HCT

  • spherocytes

  • ghost cells

  • polychromasia/reticulocytes

  • +/- nRBCs

  • agglutination

  • neutrophilia w/ L shift

• agglutination tests

  • gross autoagglutination

  • microscopic autoagglutination

  • direct agglutination test (DAT) / Coomb’s test

• chem + UA

• imaging

  • US

  • AXR

• infectious disease testing

• BM aspirate for non-regen.

Describe non-associative IMHA:

• previously called primary IMHA

• idiopathic

  • immune-mediated destruction of RBCs without identifiable cause

Describe associative IMHA:

• previously called secondary IMHA

• presumptive underlying cause/trigger ID’d

  • drugs (penicillin’s, cephalosporins, sulfa drugs)

  • vaccines

  • infectious (Rickettsia, Babesia, FeLV, fungal)

  • neoplasia

• drugs or vaccines may be associated if given ~4 weeks prior

Acute stabilization in IMHA tx:

• blood transfusion

  • indicated for life-threatening anemia or rapid declining PCV

  • avoid transfusion to “normal” PCV

    • goal is clinical improvement and stabilization

Immunosuppressive therapy in IMHA tx:

• glucocorticoids (taper after PCV stabilizes)

  • prednisone/prednisolone

  • dexamethasone

Adjunctive therapy in IMHA tx:

• secondary immunomodulatory drugs

  • azathioprine

  • mycophenolate (pIMHA)

  • cyclosporine (pIMHA)

• uncommon rescue therapies

  • hIVIG

  • splenectomy

  • plasmapheresis

  • rescue drugs

• antithrombotic therapy

  • clopidogrel

  • rivaroxaban

  • LMW heparin

Monitoring plan for IMHA tx:

• PCV

• blood smear

• agglutination

  • Coomb’s

Give examples of physiologic thrombocytopenia:

• CKCS

  • thrombocytopenia w/ macroplatelets

  • normal plateletcrit/mass

  • no clinical problems

• greyhound

  • borderline low

  • normal coags

Mechanisms of IMTP:

1. Ab against hapten-platelet membrane complex

2. specific anti-platelet Ab

3. passive absorption of preformed Ag-Ab on platelet

Etiologies of thrombocytopenia:

1. decreased production

   • BM disease

   • destruction (IMTP)

2. sequestration

   • spleen

3. consumption/loss

   • bleeding

   • DIC

4. physiologic

Signalment of IMTP in dogs and cats:

• dogs

  • adult, ~6 yo

  • females > males

  • cocker, sheepdog, poodle, German shepherd

• cats

  • less common

  • often associated with FeLV or myeloproliferative diseases

Diagnostic plan for patients with thrombocytopenia:

• CBC

  • often <10,000 platelets/uL, typically <30,000

  • secondary anemia

  • platelet morphology:

    • large platelets

    • fragmented platelets: ITP = ↓MPV

• Coomb’s test

  • if anemic and IMHA suspect

• coagulation testing

• infectious disease testing

  • FeLV/FIV, rickettsial diseases, fungal infections

List advanced diagnostics to dx ITP:

• BM aspirate

  • megakaryocyte hyperplasia if ITP

• flow cytometry

  • anti-platelet Ab’s (IgG)

Acute management of ITP:

• whole blood transfusions

• crystalloid therapy

• platelet products

  • PRP

  • platelet concentrate

Immunosuppressive and adjunctive therapies for IMTP:

• immunosuppressive

  • glucocorticoids

• adjunctive

  • enteric protection

    • omeprazole or famotidine

    • sucralfate

  • secondary immunomodulatory drug

    • mycophenolate

    • azathioprine

  • vincristine or hIVIG break up megakaryocytes

  • splenectomy

Hyperthyroidism pathophysiology:

1. normal thyroid (with few thyrocytes predestined for growth)

2. thyroid hyperplasia (susceptible thymocytes proliferating)

3. thyroid adenoma (hyperplastic nodules coalescing into adenomas)

Methimazole side effects:

• vomiting

• anorexia

• lethargy

• hepatotoxicity (icterus)

• facial swelling/excoriations

• thrombocytopenia

• neutropenia

• decompensation of azotemic CKD

Functions of thyroid hormone:

1. increase basal metabolic rate

2. stimulate lipolysis

3. stimulate gluconeogenesis and glycogenolysis

4. increase protein and enzyme synthesis

5. increase # and affinity of beta-adrenergic receptors

6. marked chronotropic and inotropic effects on heart

7. fetal development

8. stimulate erythropoiesis and bone turnover

Primary hypothyroidism thyroid panel results:

• tT4: ↓

• fT4: ↓

• TSH: ↑

• thyroglobulin autoAb’s: +/-

Secondary hypothyroidism thyroid panel results:

• tT4: ↓

• fT4: ↓

• TSH: ↓

• thyroglobulin autoAb’s: -

Non-thyroidal illness (NTI) thyroid panel results:

• tT4: ↓

• fT4: normal (unless SEVERE NTI)

• TSH: normal

• thyroglobulin autoAb’s: -

thyroglobulin autoAb’s thyroid panel results:

• tT4: ↑ (falsely)

• fT4: ↓

• TSH: ↑

• thyroglobulin autoAb’s: +

DKA clinical signs:

• anorexia, lethargy

• vomiting, decreased appetite

• hx of PUPD, weight loss, other signs associated with DM

DKA PE findings:

• dehydration

• hypovolemia

  • tachycardia

  • poor PQ, pale MM, increased CRT

  • mental dullness

• ketone breath

• signs of chronicity

  • poor BCS

  • unkempt haircoat

Glucocorticoid MOA:

• inhibit phospholipase A2 (PLA2) to:

  • inhibit production of pro-inflammatory mediators

  • ↓ leukotrienes, prostanoids

Azathioprine MOA:

• inhibit GPAT

  • interferes with de novo purine synthesis

Mycophenolate MOA:

• inhibit IMPDH

  • interferes with de novo purine synthesis

Leflunomide MOA:

• inhibit DHODH

  • interferes with de novo pyrimidine synthesis

Cyclosporine MOA:

• inhibits calcineurin

  • inhibits NF-AT activation

  • regulates gene transcription of IL-2

  • prevents T-cell proliferation

Prednisone/prednisolone and dexamethasone dose range for physiologic effect:

• Prednisone/prednisolone: 0.1-0.2 mg/kg

• Dexamethasone: 0.01-0.02 mg/kg

Prednisone/prednisolone and dexamethasone dose range for anti-inflammatory effect:

• Prednisone/prednisolone: 0.5-1.0 mg/kg or 25 mg/m²

• Dexamethasone: 0.05-0.1 mg/kg

Prednisone/prednisolone and dexamethasone dose range for immunosuppressive effect:

• Prednisone/prednisolone: 2.0 mg/kg or 50 mg/m²

• Dexamethasone: 0.2 mg/kg

Max daily dose for prednisone/prednisolone and dexamethasone:

• Prednisone/prednisolone: 50-60 mg

• Dexamethasone: 5-6 mg

Azathioprine should NOT be given to:

• Giant Schnauzers

• cats

What drug class that includes azathioprine, mycophenolate, and leflunomide should NOT be given to cats? What drug IS okay to give to cats and small dogs for immunomodulation?

cell cycle inhibitors (CCIs), cyclosporine

List second drugs for IMHA in (large) dogs or secondary immunosuppresive drugs:

• azathioprine

• mycophenolate

• leflunomide

• cyclosporine (modified if using as secondary immunosuppressive)