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.

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.

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.

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.