Sebastian syndrome is an extremely rare genetic disease that results in impaired blood clotting function and abnormal platelet formation. Another name for Sebastian syndrome is autosomal dominant macrothrombocytopenia with leukocyte inclusions.
The symptoms of Sebastian syndrome include a propensity for nosebleeds, bleeding from the gums, mildly increased bleeding time after being cut, and a tendency to bruise easily. Women may experience heavier than normal menstrual bleeding. People with Sebastian syndrome may experience severe hemorrhage after undergoing surgery for any reason. Some individuals with Sebastian syndrome may not have any observable physical signs of the disorder at all.
Diagnostic blood tests to confirm the decreased blood clotting function seen in Sebastian syndrome may include a complete blood count (CBC) to determine the number of platelets in a blood sample; blood coagulation studies; or platelet aggregation tests. There are several other disorders, including non-genetic diseases, that can cause symptoms similar to those seen in Sebastian syndrome. A family history of easy bleeding or bruising is an important clue in diagnosing Sebastian syndrome. Once the hereditary nature of the disease is confirmed, establishing a dominant inheritance pattern can separate Sebastian syndrome from other inherited giant platelet disorders. Microscopic studies of the blood can reveal the enlarged platelets and the specific shape and structure characteristics associated with Sebastian syndrome. These characteristics include a shape that is less disc-like than normal platelets. There are also bluish inclusions, or small foreign bodies, observed in the white blood cells. Genetic sequencing to confirm the presence of a mutation on the MYH9 gene is another method to positively diagnose Sebastian syndrome, although this would rarely be performed in lieu of other methods.
People with Sebastian syndrome can be expected to have a normal lifespan. The main risk for some patients is the chance of severe bleeding after surgery or injury.
No treatment is required for the majority of people affected with Sebastian syndrome. After surgery, platelet transfusion may be required in order to avoid the possibility of hemorrhage. People diagnosed with Sebastian syndrome should be made aware of the risks associated with excessive bleeding.