Hereditary Macrocytopenic Thrombocytopenia with MYH9 Mutation

Clinical case of MYH9-associated thrombocytopenia: macrothrombocytes, neutrophil inclusions, differential diagnosis with ITP, and genetic confirmation.

Editorial team 1 min November 5, 2025

Blood smear with macrothrombocytes and MYH9 gene sequencing chromatogram

🔎 Clinical Case: Hereditary Macrocytopenic Thrombocytopenia (MYH9-RD)

A 22-year-old woman presented before tonsillectomy. History includes cataracts. Her mother has “refractory ITP” with ineffective therapy, and her brother has deafness and renal failure.

🔬 Laboratory:

Platelets: 24 × 10⁹/L (normal 167–396)
Blood smear: giant platelets, blue inclusions in neutrophils (see photo ⬆️).

🎯 Diagnosis: Genetic test revealed MYH9 V1516L mutation – MYH9-associated disease (MYH9-RD) confirmed.

❗ Key features of MYH9-RD:

Autosomal dominant inheritance
Triad: macrothrombocytopenia, neutrophil inclusions, extra-hematological manifestations (cataracts, deafness, nephropathy)
Important: differentiate from ITP! Immunosuppressive treatment for MYH9-RD is ineffective.