A Novel Bone Marrow-Sampling Technique

Secondary dysmyelopoiesis—nonregenerative anemia with or without thrombocytopenia or leukopenia and an associated disease or drug treatment—has been reported in dogs after accidental toxic phenobarbital (PB) ingestion. This report describes PB-induced secondary dysmyelopoiesis in a critically ill dog diagnosed via a novel bone marrow-sampling technique. A 1.5-year-old Lhasa apso receiving PB (2.1 mg/kg PO q12h) for 6 months presented depressed, recumbent, and febrile following a week of lethargy and worsening tonic-clonic seizures. Leukopenia, thrombocytopenia, and anemia were attributed to underlying sepsis and aspiration pneumonia; however, myelodysplastic disease was suspected with continued decline of all indices despite aggressive treatment. PB was immediately discontinued and levetiracetam treatment initiated. Severe, persistent leukopenia necessitated bone-marrow sampling. The dog was placed in lateral recumbency, and using local analgesia, a 22-gauge needle attached to a 3-mL syringe was inserted at the costochondral junction of the 10th rib and advanced dorsally into the medullary cavity to aspirate bone marrow. Cytology revealed erythroid hypoplasia, megakaryocytic hypoplasia, and myeloid hyperplasia with a predominance of myeloblasts, consistent with secondary dysmyelopoiesis. Treatment was successful; by day 18, blood indices were either continuing to resolve or completely resolved and another costochondral rib aspirate revealed myeloid and erythroid precursors maturing in a normal manner. Authors concluded that costochondral bone marrow aspiration was an efficient, advantageous tool for identifying secondary dysmyelopoiesis without sedation in this critically ill patient. Prognosis for this condition appears to be good with prompt identification and discontinuation of PB.

Commentary

Epilepsy is common in dogs, and treatment with PB is a common first-line anticonvulsant agent. This report is a reminder PB may be associated with a reversible pancytopenia; this is crucial because non-reversible causes of pancytopenia are almost universally associated with a grave prognosis. Also, remember the tenet do no harm; that is, avoid sedation or anesthesia that could compromise the patient’s clinical course. This novel technique for a bone marrow aspirate may be useful in a variety of cases.—Elizabeth Rozanski, DVM, DACVIM, DACVECC