Cause:Genetic, autosomal dominant; or acquired, eg, with lymphoma (Nejm 1978;298:988)
Pathophys:
Von Willebrand protein normally complexes and circulates with factor VIII, which enhances synthesis of VIII, protects it from proteolysis, and concentrates it at sites of active homeostasis (Nejm 1994;330:38)
Platelets have decreased adhesiveness, probably due to a coenzyme deficiency, normally provided by factor VIII. No factor VIII inhibitors develop
Types (Nejm 1983;309:816): I = decrease in VIII protein; IIA and IIC = decreased ability to form large VIII multimers; IIB = increased removal rate of large multimers
Prevalence = 1/25 000. Associated with mitral valve prolapse and Marfan's, both inherited connective tissue defects (Nejm 1981;305:131)
Sx:Bleeding, some menstrual and/or birth-related bleeding despite normal increase in VIII during pregnancy
Si:Severe bleeding from abrasions, mucous membranes, postsurgery; rarely into joints like true hemophiliacs
Lab:
Hem:VIII deficiency by levels and clot workup (Screening Tests of Clotting Function); antigen/function ratio 
1, unlike hemophilia (Ann IM 1978;88:403)
Clotting studies: normal PT and platelets normal; PTT prolonged; bleeding time may be normal, but not after ASA when BT >15 min reliably, normals don't (D. Deykin, 1978); ristocetin test shows abnormal platelet function
Immunol: Deficient von Willebrand's factor by immunoassay, also called "factor VIII antigen"
Rx:
(Nejm 2004;351:683)
Avoid ASA, indomethacin, phenylbutazone, and other NSAIDs
Keep trough factor VIII levels >30% for minor surgery and spontaneous bleeds; keep >50% for major surgery, ob delivery and dental extractions
Desmopressin (DDAVP) (vasopressin analog) (for dosing, see rx above Classic Hemophilia (Hemophilia A) for hemophilia), for type I and IIA only, worsens other types through platelet aggregation (Ann IM 1985;103:228; Med Let 1984;26:82)
Factor VIII w vonW factor content, eg, Humate-P