VELOCARDIOFACIAL SYNDROME PATIENTS WITH A HETEROZYGOUS CHROMOSOME 22Q11 DELETION HAVE GIANT PLATELETS

Patients with a microdeletion on chromosome 22q11 demonstrate the clin ical picture of the velocardiofacial syndrome. We report on three memb ers of the same family with this microdeletion and velocardiofacial sy ndrome, all having an increase in platelet size and a mild decrease in platelet number. Their platelet function, however, tested by aggregat ion and by adherence to collagen in a whole blood perfusion system, wa s normal. We retrospectively studied the files of 35 other patients wi th 22q11 deletion and also found that their platelets had an increased size compared with cardiac controls. Moreover, their platelet size co rrelated negatively with platelet number. Knowing that pa patients wit h 22q11 deletion are obligate carriers for a heterozygous glycoprotein IbP deletion, these patients can be considered to be heterozygous Ber nard-Soulier patients. In addition, a significant increase in platelet size may be a positive predictor for the clinical diagnosis of the ve locardiofacial syndrome.