Comparison of Different Phenotypes of Bernard-Soulier Syndrome

Introduction. Bernard-Soulier syndrome (BSS) is one of the rare inherited platelet disorder. It is caused by deficiency or defect of the glycoprotein (GP) Ib-IX-V complex on the surface of platelets - the main receptor for von Willebrand factor (vWF). Dissociation of hemostasis in BSS leads to microcirculatory and mixed types of bleeding episodes - mucocutaneous bleedings, spontaneous and posttraumatic hematomas and severe hemorrhagic episodes during surgery.

Materials and methods. We diagnosed 2 Caucasian women of age 32 and 29 years (patient 1 and patient 2 with different phenotypes of BSS) using total blood count, clotting time tests, fibrinogen, platelet aggregation with ristomicin, ADP, collagen, arachnid acid, adrenaline, platelet morphology analysis and flow cytometry assay. Flow cytometry assay was performed on isolated from 3 mL of citrated blood platelets. Platelets were loaded with mepacrine (1 mM) and then stimulated with thrombin at 88 nM. Samples from 10 healthy donors were used as controls. We evaluated CD61, PAC1, CD42b, mepacrine, CD62p, annexin V on active and non-active platelets.

Results. Both patients had similar results in standard coagulation test: normal or shortened APTT (26-29 sec), normal fibrinogen (1.8-2.5 g/l), increased activity of vWF (209-275%) and FVIII (140-287%). Data of light aggregometry was classic for BSS: decrease of platelet aggregation with ristomicin and normal with other parameters. The peripheral blood smear showed large platelets and absence of neutrophil inclusions.

Despite similarity of primary laboratory analysis patient 1 and patient 2 have very different phenotypes of BSS. Patient 1 had first clinical manifestation at age of 2 - large posttraumatic hematomas and then was treated from ITP without any results. At age of 13 menorrhagia had started and was slightly managed by prescribing hormonal therapy. At 16 yrs she had hemorrhage into the abdominal cavity. A therapeutic laparotomy was performed, complicated by the development of bleeding in the early postoperative period. At age of 31, the patient was hospitalized with a diagnosis of acute cerebrovascular accidents of hemorrhagic type with the formation of subdural hematoma with a repeated spontaneous brain hemorrhage in 1 month.

Patient 2 was diagnosed with BSS at age of 6 yrs. Clinical pictures is characterized by menorrhagia from age of 14 yrs, that normalized at age of 20. Although she was hospitalized for many times due to severe anemia (Hb 40-50 g/l) of unknown reason. At age of 29 patient 2 was diagnosed with angiectasia of jejunum that appeared to be hidden source of blood loss. After treating it with eptacog alfa (activated) and proscribing gastrointestinal therapy anemia syndrome was managed.

We compared the results of flow cytometry of patient 1 and patient 2. СD42b was 0% in both patients. Patient 1 also had a deficiency of dense granules of platelets and elevated levels of CD 61 and CD62. Patient 2 had no other platelet deficiencies and highly elevated parameters of CD61, PAC1, mepacrine, CD62p (up to 3 times).

Conclusions. The compensatory high activation of other components of platelets in patient 2 can be evaluated as a result of a mild phenotype. Combined defect of BSS and deficiency of dense granules also can be a result of severe hemorrhage in patient 1. It is important to include flow cytometry of platelets in standard algorithm of diagnostic to evaluate more correctly the phenotype of platelet disorders.