Immuno 2, Diagnosis of Autoimmune Diseases Flashcards
What are the 4 major autoimmune diseases of dogs and cats and what is the specific immunological abnormality present in each?
- Autoimmune hemolytic anemia (IMHA): auto-Ab directed against RBC surface Ags
- Immune-mediated thrombocytopenia (IMTP): auto-Ab against platelet Ag
- Immune-mediated polyarthritis (IMPA): auto-Abs or cross-reactive Abs against poorly defined Ags present in the synovium
- Systemic lupus erythematosis (SLE): auto-Abs directed against nuclear Ag (DNA, RNA, histones)
What common diseases are actually primary immune-mediated diseases?
- DM: immune-mediated destruction of islet cells
- Hypothyroidism: immune-mediated destruction of thyroglobulin producing cells
- Hypoparathyroidism: immune-mediated destruction of parathyroid gland cells
- Addison’s: immune-mediated destruction of adrenal cortical cells (some or all layers)
- Equine periodic opthalmia: immune-mediated injury to iris, posterior chamber
- Rheumatoid arthritis: immune-mediated injury to small joints
- Blistering skin diseases (BP, PVU, DL): immune-mediated injury to epithelial cells and junctions
Are there other diseases where immune responses are an important mediator of disease pathology?
- Septic shock: cytokine responses to bacterial infection or tissue damage - all spp
- Viral or bacterial meningitis and encephalitis - all spp
- OA - all spp
- Chronic active hepatitis - dog
- IBD - dog and cat
- Allergic airway disease - cat and horse
- Atopy and flea allergy - dog, cat, horse
How do we diagnose IMHA?
- typical hx and signalment: fairly acute onset, young to middle-aged female dog
- hemogram: regenerative anemia, spherocytes, agglutination
- leukogram: high WBC, mature neutrophilia; often concurrent thrombocytopenia
- Chem: bilirubinemia, hypoalbuminemia
What does the Comb’s test measure?
Coomb’s test = direct antiglobulin test (DAT)
- measures presence of IgG on surface of patient RBC, using microagglutination assay
- RBC IgG can also be measured and quantitated more precisely using Flow Cytometry
- FC preferred extra diagnostic test for IMHA (usually we don’t need this step)
What are the major negative prognostic findings in dogs with IMHA?
- concurrent thrombocytopenia
- hyperbilirubinemia
- elevated WBC and neutrophilia with inc bands
- inc BUN
- dec serum albumin
- MONOCYTOSIS
What is the single most predictive factor for IMHA?
Monocytosis
What is a typical hx or an animal with IMTP?
- typical signalment: young to middle-aged female
- presence of petechia
- unexplained hematuria or epistaxis or hematachezia
- unexplained (regenerative) anemia
How is IMTP diagnosed?
- document thrombocytopenia
- *magnitude of thrombocytopenia does NOT predict whether IMTP or other causes of platelet destruction or consumption
- ** very low platelet counts can occur in animals with platelet destruction due to causes other than anti-platelet Abs
- animals with IMTP can also have only mildly dec platelet counts
- R/O other causes of thrombocytopenia
- BM exam rarely helps
Key diagnostic test = Flow cytometry for anti-platelet Abs
What are causes of thrombocytopenia?
- IMTP
- Rickettsial infection
- DIC
- blood clots
- drug hx
- estrogens
- occult neoplasia
What is a typical hx for an animal with IMPA?
- young animal, acute to sub-acute onset
- intermittent fever
- shifting leg lameness
- general malaise, inappetance, lack of activity
- *Joint effusion often can’t be palpated!!
What is a typical history for an animal with SLE?
- chronic illness, young to middle-aged animal
- many different manifestations (looks like anything!), including skin lesions, PA, myopathy, CNS signs
- fever often present intermittently
What lab abnormalities are often found in SLE patients?
- anemia (regen or non-regen)
- mild thrombocytopenia
- neutropenia
- high liver enzymes
- proteinuria
- high globulins
How is SLE diagnosed?
Typical patient with combo of 4 or more clinical or lab abnormalities
ANA (anti-nuclear Ab test) helpful if positive, but negative doesn’t R/O
How is rheumatoid arthritis diagnosed?
- typical rad findings: erosive joint disease, small, distal joints
- RA test: measures IgM Abs directed against Fc portion of IgG Ab
- Serology for detection of Ab to citrullinated proteins
- Joint taps: can’t be used to distinguish RA from PA
