title: Asymptomatic macrothrombocytopenia in a young pure-bred beagle dog: a case report.
abstract: During baseline evaluation prior to a preclinical safety study, a 10-month-old male pure-bred Beagle dog was found to have marked thrombocytopenia (6 × 10(3) platelets [PLT]/µL) associated with a mean platelet volume (MPV) of 17.9 fL. Tests for Rickettsia rickettsii, Ehrlichia canis, and Borrelia burgdorferi were negative. Buccal bleeding time was normal. Over 3 months, PLT were 4 to 141 × 10(3) PLT/µL, and MPV was 11.4 to 25.1 fL; however, PLT were <50 × 10(3) PLT/µL and MPV was >16 fL during most of this period. Antinuclear antibody (ANA) and anti-PLT antibody tests were negative. Genotyping for the presence of a beta 1-tubulin mutation demonstrated the normal wild-type gene. Treatment with prednisone resulted in normal values after only 3 days. Ultrastructure of enlarged PLT was consistent with that of immature PLT, characterized by reduced numbers of peripheral microtubules and the presence of rough endoplasmic reticulum, free ribosomes, Golgi apparatus, and a prominent canalicular system. PLT ultrastructure and glucocorticoid responsiveness supported a diagnosis of immune-mediated thrombocytopenia that was masked by the cyclic nature of PLT decreases and lack of clinical signs. Inclusion of such a dog in a preclinical safety study could result in misinterpretation of clinical pathology findings.
authors.affiliation: Abbott GmbH & Co KG, Preclinical Safety, Ludwigshafen, Germany. karen.bodie@abbott.com
authors.forename: Karen
authors.initials: K
authors.lastname: Bodié
authors.forename: Gerard D
authors.initials: GD
authors.lastname: Gagne
authors.forename: Mary K
authors.initials: MK
authors.lastname: Sramek
authors.forename: David J
authors.initials: DJ
authors.lastname: Desmond
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Abel
authors.forename: Jane A
authors.initials: JA
authors.lastname: Fagerland
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000166:cytology / Q000648:ultrastructure; D025065:Borrelia burgdorferi / Q000302:isolation & purification; D004285:Dogs; D041061:Ehrlichia canis / Q000302:isolation & purification; D004912:Erythrocytes / Q000378:metabolism; D005838:Genotype; D005938:Glucocorticoids / Q000378:metabolism; D008297:Male; D046529:Microscopy, Electron, Transmission; D010976:Platelet Count; D011241:Prednisone / Q000627:therapeutic use; D012284:Rickettsia rickettsii / Q000302:isolation & purification; D013921:Thrombocytopenia / Q000175:diagnosis* / Q000503:physiopathology*
chemical_list: D005938:Glucocorticoids; D011241:Prednisone