Bernard-Soulier Syndrome Sequence Analysis

top title margin BERNARD-SOULIER SYNDROME SEQUENCE ANALYSIS

BloodCenter of Wisconsin offers full-length DNA sequencing of glycoprotiens Iba, Ibβ and IX for diagnosis of Bernard-Soulier Syndrome.

BACKGROUND: Bernard-Soulier Syndrome (BSS) is a rare inherited bleeding disorder due to absence or dysfunction of the platelet glycoprotein receptor Ib/V/IX complex. Laboratory evaluation typically reveals (1) mild to moderate thrombocytopenia, (2) unusually large platelets and (3) abnormal platelet function with absent or markedly reduced aggregation response to ristocetin. Flow cytometric analysis generally demonstrates absence of GPIb (CD 42) on the platelet surface although rare patients with detectable glycoprotein expression (variant BSS) have also been described.

The GPIb/V/IX complex is a receptor for von Willebrand factor on platelets, enabling platelet adhesion at sites of vascular injury. GPIbα, GPIbβ and GPIX, encoded by the GP1BA, GP1BB and GPIX genes, are all required for efficient expression of the complex on the platelet surface, while absence of GPV does not appear to affect receptor expression or VWF binding.

Most cases of BSS are inherited as an autosomal recessive genetic trait. Defects have been identified in GP1BA (17q12), GP1BB (22q11, within the DiGeorge critical region) and GPIX (3q29). There are no reported cases of BSS associated with defects of the GPV gene (3q21).

METHOD: PCR and bidirectional DNA sequence analysis of the coding region and intron-exon borders.

REASONS FOR REFERRAL: Genetic analysis is useful to confirm a diagnosis of BSS, and may be helpful for genetic evaluation of family members.

SPECIMEN REQUIREMENTS: 5 ml EDTA (lavender top) whole blood. Sample must be less than 1 month old when received in our laboratory. ASSAY SENSITIVITY AND SPECIFICITY Analytical sensitivity and specificity is approximately 99%. The method detects nucleotide base alterations, small deletions and insertions within the regions analyzed. Large deletions and duplications have not been described in this disorder and are not detected by this assay. Rare sequence variations in primer binding sites may interfere with mutation detection.

Clinical sensitivity will be highest in patients with a phenotype consistent with the disorder. A positive test result confirms a diagnosis of BSS. Heterozygous carriers may be affected. A negative test results argues strongly against a diagnosis of BSS.

TURNAROUND TIME: 21 days

CPT CODES: 81479

SHIPPING REQUIREMENTS: Ship on an ice pack or at room temperature. Place the specimen and the requisition into plastic bags and seal. Insert into a Styrofoam container; seal and place into a sturdy cardboard box, and tape securely. Ship the package in compliance with your overnight carrier guidelines. Label with the following address:

Client Services/Hemostasis Reference Laboratory BloodCenter of Wisconsin 638 N. 18th St. Milwaukee, WI 53233 Phone: 800-245-3117, ext. 6250

ALSO AVAILABLE: Platelet Glycoprotein Expression (determines the presence of the GPIb/V/IX complex on platelets by flow cytometry)

REFERENCES: • Nurden AT, George JN. Inherited abnormalities of the platelet membrane: Glanzmann thrombasthenia, Bernard-Soulier syndrome, and other disorders. In: Colman RW, Marder VJ, Clowes AW, George JN, Goldhaber SZ (eds) Hemostasis and Thrombosis: Basic Principles and Clinical Practice. Philadelphia: Lippincott Williams & Wilkins, 2006. • Lopez JA, Andrews RK, Afshar-Kharghan V, Berndt MC. Bernard-Soulier syndrome. Blood 1998:91: 4397-4418. • Dong J-F, Gao S, Lopez JA. Synthesis, assembly, and intracellular transport of the glycoprotein Ib-IX-V complex. J Biol Chem 1998:273: 31449-31454. • Ulsemer P, Strassel C, Baas MJ et al. Biosynthesis and intracellular post-translational processing of normal and mutant platelet glycoprotein GPIb-IX. Biochem J 2001:358: 295-303.

January 2013