May-Hegglin anomaly in a dog

Vet Clin Pathol. 2011 Jun;40(2):207-14. doi: 10.1111/j.1939-165X.2011.00320.x. Epub 2011 May 9.


An 8-year-old female spayed Pug dog was presented for evaluation of cutaneous lesions occurring secondary to immunosuppressive treatment of presumed immune-mediated thrombocytopenia. Abnormal hematologic findings included persistent thrombocytopenia, macrothrombocytes, and variably shaped, often fusiform, blue cytoplasmic inclusions in neutrophils. May-Hegglin anomaly (MHA) was suspected based on the morphologic appearance of platelets and neutrophils. Examination of cells by transmission electron microscopy revealed normal platelet ultrastructure; neutrophil inclusions had features similar to those reported for inclusions in human MHA. Neutrophil function was within normal limits based on flow cytometric analysis. Thrombelastography indicated a prolonged clotting time (r), and PlateletMapping showed a lack of response to 2 μM ADP compared with a moderate response in the control dog. Immunocytochemical staining of blood smears using 2 commercially available antibodies against MYH9 protein (nonmuscle myosin heavy chain II) yielded negative results. However, genomic DNA sequencing analysis of the dog's MYH9 gene identified a single point mutation, resulting in substitution of lysine for glutamine at the 1841 amino acid position; this mutation is identical to one identified in people with MHA. To our knowledge, this is the first report of an MYH9 mutation in the dog. MHA-associated macrothrombocytopenia may be mistaken for immune-mediated thrombocytopenia.

Publication types

  • Case Reports

MeSH terms

  • Animals
  • Blood Platelets / ultrastructure
  • Dog Diseases / blood*
  • Dog Diseases / genetics
  • Dogs
  • Female
  • Hearing Loss, Sensorineural
  • Microscopy, Electron, Transmission / veterinary
  • Myosin Heavy Chains / genetics
  • Point Mutation / genetics
  • Thrombelastography / veterinary
  • Thrombocytopenia / blood
  • Thrombocytopenia / genetics
  • Thrombocytopenia / veterinary*


  • Myosin Heavy Chains

Supplementary concepts

  • MYH9-Related Disorders