The gray platelet syndrome (GPS) is a rare inherited bleeding disorder characterized by thrombocytopenia, splenomegaly, myelofibrosis, and a marked decrease or absence of alpha-granules and platelet-specific alpha-granule proteins. In GPS patients, the platelets appear large and contain few granules, giving them a gray appearance on Wright-stained smears. GPS has been described in both males and females. The disorder has been reported as autosomal dominant, but in several cases a recessive inheritance was suggested.
Gray platelet syndrome (GPS) is linked to mutations in the NBEAL2 gene on chromosome 3p21. NBEAL2 belongs to the BEACH (beige and CHS1) domain-containing protein family, which includes NBEAL1, neurobeachin (NBEA), CHS1 (LYST), and LRBA. NBEAL2 is predicted to have a role in alpha-granule biogenesis in megakaryocytes.