Gray Platelet Syndrome in a Somalian family.

The Gray Platelet Syndrome (GPS) is a rare inherited, hypogranular platelet disorder characterized by virtual absence of alpha granules in bone marrow megakaryocytes and circulating plates. Usually only one member of a family is affected, but families with two or more affected individuals have been reported from France, Australia, and Mexico, and, recently, the United States. The current study has evaluated the first family from East Africa with two affected members, a brother and sister. Neither child has had significant bleeding problems. Electron microscopic studies revealed almost complete absence of alpha granules from their platelets. Instead their platelets were filled with vacuoles similar in size to the missing granules. Dense bodies were normal in number in the girl's platelets, but markedly increased in her brother's cells. Tannic acid staining revealed that very few of the vacuoles were connected to channels of the open canalicular system. As a result, contents of the residual alpha granule vacuoles must leak out of the organelles and diffuse through megakaryocyte and platelet cytoplasm to the outside. The route of escape may differ from other hypogranular platelet syndromes, such as alpha-delta platelet storage pool deficiency.