Hereditary macrothrombocytopenia with leukocyte inclusions resembling Döhle bodies (May-Hegglin anomaly) described in a Pug: giant platelets in peripheral blood and moderate thrombocytopenia, generally asymptomatic except for mild bleeding after surgery or trauma. It is associated with a MYH9 variant identical to a human one (p.Q1841K), described in a single published canine case. Test available by sequencing (referred to an external laboratory).

Rare: a single published canine case (Pug, Flatland 2011). No population frequencies.

- Moderate thrombocytopenia on blood count\n- Macroplatelets in peripheral blood\n- Döhle bodies in neutrophils (leukocyte inclusions)\n- Generally no clinical signs\n- Possible mild bleeding after surgery or trauma\n- Prolonged bleeding time in some cases

Human May-Hegglin syndrome was linked to MYH9 in the late 1990s. In the dog, Flatland et al. (2011) described a Pug with macrothrombocytopenia and leukocyte inclusions in which MYH9 sequencing identified p.Q1841K, identical to a human variant: the first and only published canine case with MYH9. A sequencing test exists for the Pug. In other breeds, hereditary macrothrombocytopenias are caused by other genes (TUBB1 in Cavalier, Norfolk and Cairn).

- In the face of macrothrombocytopenia with leukocyte inclusions in a Pug, confirm by blood smear and immunocytochemistry before attributing it to an immune-mediated cause.\n- The test is a supportive diagnostic in compatible cases, not a population screening (a single published case).\n- Inform the referring veterinarian before any scheduled surgery.\n- Do not make breeding decisions based only on this test without a compatible clinical picture.

Distinguish from immune-mediated thrombocytopenia (IMTP), from pseudothrombocytopenias due to aggregation and from macrothrombocytopenias of other breeds (TUBB1). Automated counting underestimates giant platelets: verify with a blood smear. MYH9 immunocytochemical staining on smears is informative. Notify the laboratory before surgery.

1. Flatland B et al. 2011, anomalía de May-Hegglin en un perro con mutación MYH9 p.Q1841K (PMID 21554370)