Sebastian platelet syndrome, or SPS, is a rare disease similar to some other inherited giant platelet disorders. It is characterized by moderately enlarged platelets, malformations in some white blood cells and thrombocytopenia, which is a low platelet count. SPS was first described in 1990 and a review in the "American Journal of Clinical Pathology" reports that only four cases had been identified by the year 2000.
Genetics
An 2001 article in the journal "Blood" reports that SPS is the result of a mutation in a gene that encodes for a protein that controls cell movement. SPS is a dominant genetic disorder, which means that only one parent needs to have the mutation to pass the disorder on to his children.
Normal Platelet Function
Platelets, also called thrombocytes, are fragments of megakaryocyte cells and are produced in the bone marrow. They circulate in the blood and participate in hemostasis, which is the process of preventing bleeding. Platelets plug up holes in damaged blood vessels and secrete factors that promote clot formation. The lifespan of platelets is typically less than ten days.
Thrombocytopenia
A platelet count is a routine measurement taken during annual blood examinations. MayoClinic.com reports a normal platelet count ranges between 150,000 and 450,000 platelets per microliter of blood. The 2000 "American Journal of Clinical Pathology" review reports that people with SPS have mild to moderate thrombocytopenia, with platelet counts between 40,000 and 120,000 platelets per microliter of blood. This review also notes that bleeding times in SPS patients are prolonged by 10 to 12 minutes.
Symptoms
The "American Journal of Clinical Pathology" review also notes that the symptoms of SPS are mild and that some people with SPS may not have any symptoms at all. The frequency of nosebleeds and bruising may be increased. During and after surgery, people with SPS should be monitored for hemorrhage. People with this disorder do not have cataracts, kidney disease or deafness, which are common in similar disorders.
Diagnosis
SPS is diagnosed by conducting a microscopic study of blood samples. In this disorder, platelets are moderately enlarged and shaped differently from normal platelets. Other white blood cells contain foreign bodies. Genetic sequencing can be performed to detect the specific mutation associated with this disorder and confirm the diagnosis. This disorder does not require treatment except for the prevention of serious hemorrhage during and following surgery.
References
- "Mayo Clinic Proceedings"; Sebastian Platelet Syndrome; Vilmarie Rodriguez et al.; November 2003
- MayoClinic.com: Thrombocytopenia
- "Blood"; Mutations in the NMMHC-A Gene Cause Autosomal Dominant Macrothrombocytopenia with Leukocyte Inclusions; Shinji Kunishima et al.; February 2001
- "American Journal of Hematology"; Sebastian Syndrome; Guy Young et al.; April 1999
- "American Journal of Clinical Pathology"; Inherited Giant Platelet Disorders; Paula Mhanwech and Abdus Saleem; February 2000
