Sebastian syndrome

Sebastian syndrome
portrait of Fernando Martínez Sáez
Written by

Fernando Martínez Sáez
Medically reviewed by our Medical staff

Last update: 01-04-2022

How else can it be called?

  • Autosomal dominant macrothrombocytopenia with leukocyte inclusions

  • ICD-10: D69.1

What is Sebastian syndrome?

Sebastian syndrome is a rare genetic disorder characterized by enlarged platelets and a low platelet count in the blood that results in a reduced blood clotting function.

Sebastian syndrome is classified as one of the inherited giant platelet disorders (IGPDs), along with Bernard-Soulier syndrome, May-Hegglin anomaly or grey platelet syndrome. Lekcocytes, in Sebastian syndrome, have inclusions called Döhle bodies.

Affected people may bruise easily due to a decreased blood clotting function.

What are the main causes?

Sebastian syndrome is a genetic disorder due to a mutation in the gene MYH9, located in chromosome 22 (22q12.3) that encodes a specific enzyme known as non-muscle myosin heavy chain IIA.

Sebastian syndrome is an inherited disease with an autosomal dominant pattern. It means that just one defective copy of a gene (from the father or the mother) is required to cause the disorder.

What are the main symptoms of Sebastian syndrome?

Sebastian syndrome stands out by specific features of the cellular components of the blood:

  • Mildly enlarged platelets.
  • Thrombocytopenia (a low platelet count).
  • Bluish inclusions or small foreign bodies observed in the white blood cells (Döhle bodies).

Due to the abnormal platelet features, the most common symptoms are:

  • Frequent nosebleeds.
  • Bleeding gums.
  • Prolonged bleeding after a cut or wound.
  • Heavier than normal menstrual bleeding in women.

What is the recommended treatment?

In general, no treatment is required in people affected by Sebastian syndrome.

In case of surgery, a platelet transfusion may be necessary to avoid excessive bleeding.

Medically reviewed by our Medical staff on 01-04-2022


  • The Gale Encyclopedia of genetic disorders. 2002. Stacey L. Blachford. Vol 2. pag 1037. ISBN 0-7876-5612-7.

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