Summary
Genetic defects of the megakaryocyte lineage give rise to bleeding syndromes of varying
severity. Blood platelets are unable to fulfill their hemostatic function of preventing
blood loss on vessel injury. Spontaneous bleeding is mostly mucocutaneous in nature.
Most studied are deficiencies of glycoprotein (GP) mediators of adhesion (Bernard-Soulier
syndrome) and aggregation (Glanzmann thrombasthenia) which concern the GPIb-IX-V complex
and the integrin αIIbβ3, respectively. Defects of primary receptors for stimuli include
the P2Y12 ADP receptor pathology. Agonist-specific deficiencies in the platelet aggregation
response and abnormalities of signaling pathways are common and lead to trauma-related
bleeding. Inherited defects of secretion from storage organelles, of ATP production,
and of the generation of procoagulant activity are also encountered. In some disorders,
such as the Chediak-Higashi, Hermansky-Pudlak, Wiskott-Aldrich and Scott syndromes,
the molecular lesion extends to other cells. In familial thrombocytopenia (FT), platelets
are produced in insufficient numbers to assure haemostasis. Some of these disorders
affect platelet morphology and give rise to the so-called ‘giant platelet’ syndromes
(MYH9-related diseases) with changes in megakaryocyte maturation within the bone marrow
and premature release of platelets. Diseases of platelet production may extend to
other cells and in some cases interfere with development. Transfusion of platelets
remains the most common treatment of severe bleeding, management with desmopressin
is common for mild disorders. Substitute therapies are available including rFVIIa
and the potential use of TPO analogues for FT. Stem cell or bone marrow transplanation
is being used for severe diseases while gene therapy may be on the horizon.
Keywords
Platelets - inherited disorders - platelet function - platelet production - treatment