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672 Myelodysplasia

CONTAGION AND ZOONOSIS DIAGNOSIS ○ Bizarre nuclear morphologies resembling
FeLV and FIV: contagious between cats Diagnostic Overview bowling pins, doughnuts, or abnormally
VetBooks.ir Clinical Presentation History and physical findings are nonspecific, • Serum biochemistry profile and urinalysis:
small nuclei
DISEASE FORMS/SUBTYPES
no specific abnormalities
but CBC usually reveals at least one repeatable
Primary (no inciting cause known) or sec-
marrow exam performed because of persistent
ondary (specific causative agent). MDS is abnormality. The diagnosis is obtained on bone • All cats with MDS should be tested for FeLV
and FIV.
classified as three subtypes based on cytologic peripheral blood cell abnormalities without an
exam of bone marrow. Although this classifi- identifiable cause. Additional tests for underly- Advanced or Confirmatory Testing
cation offers quantification of blast popula- ing causes (e.g., titers for rickettsial diseases) • Cytochemical stains, immunohistochemi-
tions, it does not provide specific prognostic may be indicated. cal stains, and/or flow cytometry may be
information. useful to rule out myeloid and lymphoid
• MDS-ER (erythroid predominant): myeloid Differential Diagnosis malignancies.
to erythroid (M:E) ratio < 1, blasts < 20% • Acute leukemia • Ehrlichia and Anaplasma spp titers if
of nucleated bone marrow cells • Drug-induced bone marrow dyscrasia indicated
• MDS-RC (refractory cytopenia): M:E ratio • Hyperplasia of recovering bone marrow • Serum iron, zinc, lead, and vitamin B 12 /folate
> 1, nonerythroid blasts < 5% of nucleated • Nonregenerative anemia from chronic/ levels, as indicated
bone marrow cells inflammatory disease, renal disease, iron • Coombs’ test to rule out antibodies directed
• MDS-EB (excess blasts): M:E ratio > 1, deficiency, drugs or toxins, or aplastic anemia against red blood cells
nonerythroid blasts 5%-19% of nucleated • Neutropenia: tissue demand, endotoxemia/
bone marrow cells sepsis, immune-mediated destruction, TREATMENT
inherited/genetic leukocyte maturation/
HISTORY, CHIEF COMPLAINT function abnormalities Treatment Overview
• Nonspecific clinical signs related to anemia, • Thrombocytopenia: drug therapy, immune- Therapy includes supportive care (if needed)
including weakness, lethargy, tachypnea, and mediated destruction until cytopenias resolve. Overall goals are to
appetite changes (ranging from anorexia to • Rickettsial (Ehrlichia and Anaplasma spp, restore normal hematopoiesis, treat underly-
pica) Rocky Mountain spotted fever) organism- ing cause (if appropriate), and eradicate
• Recurrent/chronic infections if leukopenia induced bone marrow dyscrasias dysplastic blast cells or neoplastic cells as
or abnormal leukocyte function occurs • Congenital conditions associated with possible.
• Bruising/bleeding secondary to thrombocy- dysplastic features
topenia or platelet function disorders ○ Miniature and toy poodles: familial Acute General Treatment
• Drug history is important for identifying nonanemic macrocytosis with dysplastic • Discontinue all drugs, especially agents
possible triggers. changes in erythroid precursors associated with MDS.
○ English springer spaniels: congenital • Intensive supportive care may be warranted
PHYSICAL EXAM FINDINGS dyserythropoiesis, polymyopathy, and for patients with severe cytopenias.
• Weakness, tachycardia, syncope, heart cardiac disease ○ Transfusions (p. 1169)
murmurs, and pallor may indicate anemia. ○ Giant schnauzers: congenital malabsorp- ○ Antibiotics for treating/preventing second-
• Fever due to secondary infections tion of vitamin B 12 and myelodysplasia ary infections
• Epistaxis or petechiae due to thrombocyto- ○ Cavalier King Charles spaniels, Norfolk ■ For prophylaxis, a common choice
penia or abnormal platelet/megakaryocyte and Cairin terriers: idiopathic sub- is trimethoprim-sulfadiazine 15 mg/
maturation clinical thrombocytopenia and dysplastic kg PO q 12h (for dogs; cats do not
• Hepatomegaly and splenomegaly are changes in megakaryocytes and platelets usually need prophylactic antibiotics).
common in cats and may occur in dogs. (macroplatelets) ■ If fever or overt infection is present,
• Pleural effusion, possibly leading to muffled IV broad-spectrum antibiotics, based
heart and lung sounds, has been reported in Initial Database preferably on culture and sensitivity or
cats. • CBC: cytopenias and dysplastic blood cell empirical use, are indicated. Example: a
morphology. Blood smear must be reviewed by combination of a penicillin (e.g., ampi-
Etiology and Pathophysiology a clinical pathologist for accurate assessment. cillin 22 mg/kg IV q 8h slow bolus)
• MDS may be primary (presumably due ○ Nonregenerative anemia: often with many with an aminoglycoside (e.g., amikacin
to mutations in hematopoietic progenitor nucleated red blood cells; thrombocyto- 20 mg/kg IV q 24h [only in hydrated
cells) or secondary (associated with FeLV penia and/or leukopenia often present patient without renal dysfunction]) or
or FIV infections, drug therapy, or disorders ○ Leukocyte abnormalities: ringed nuclei, a fluoroquinolone (e.g., enrofloxacin 5
such as lymphoma, multiple myeloma, micronuclei, nuclear fragments, abnormal mg/kg diluted 1:1 in sterile water and
myelofibrosis, or immune-mediated anemia/ cytoplasmic granulation, or maturation given as a slow IV bolus q 12h [dogs]; 5
thrombocytopenia). arrest mg/kg q 24h in cats, but use judiciously
• In FIV-infected cats with peripheral ○ Giant platelets and dwarf megakaryocytes in cats due to retinotoxic risk).
cytopenias, FIV can be isolated from bone • Bone marrow evaluation (biopsy is often ○ IV fluid therapy for patients with infec-
marrow mononuclear cells, megakaryocytes, superior to aspiration for establishing most tion, fever, dehydration, or decreased
and marrow stromal cells. accurate detail of bone marrow cellularity appetite
• A variety of chromosomal abnormalities and and marrow architecture) (p. 1068). ○ Avoid jugular venipuncture or catheteriza-
mutations in oncogenes and tumor suppres- ○ Exam of bone marrow is necessary to tion in cases of severe thrombocytopenia.
sor genes have been identified in humans confirm MDS and identify the subtype. ○ Nutritional support
with MDS but have not been demonstrated ○ By definition, < 20% of the marrow • Recombinant granulocyte colony-stimulating
in animals. nucleated cells are blast cells (if > 25% factor (G-CSF) 5 mcg/kg SQ q 24h until
• MDS-associated clonal proliferation, apopto- blasts, the diagnosis is acute leukemia, neutrophil count normalizes, recombinant
sis, and ineffective hematopoiesis can result and the prognosis is usually worse). human erythropoietin (rh-Epo, Epogen)
in lethal cytopenias, or MDS may progress ○ Asynchrony of nuclear and/or cytoplasmic 100 IU/kg SQ q 48-72h until hematocrit
to acute leukemia. maturation of affected cell lines rises, then q 7 days or as needed to maintain

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