RESUMO
Platelet function is developmentally regulated. Healthy neonates do not spontaneously bleed, but their platelets are hypo-reactive to several agonists. The mechanisms underlying immature platelet function in neonates are incompletely understood. This critical issue remains challenging for the establishment of age-specific reference ranges. In this study, we evaluated platelet reactivity of five pediatric age categories, ranging from healthy full-term neonates up to adolescents (11-18 years) in comparison to healthy adults (>18 years) by flow cytometry. We confirmed that platelet hypo-reactivity detected by fibrinogen binding, P-selectin, and CD63 surface expression was most pronounced in neonates compared to other pediatric age groups. However, maturation of platelet responsiveness varied with age, agonist, and activation marker. In contrast to TRAP and ADP, collagen-induced platelet activation was nearly absent in neonates. Granule secretion markedly remained impaired at least up to 10 years of age compared to adults. We show for the first time that neonatal platelets are deficient in thrombospondin-1, and exogenous platelet-derived thrombospondin-1 allows platelet responsiveness to collagen. Platelets from all pediatric age groups normally responded to the C-terminal thrombospondin-1 peptide RFYVVMWK. Thus, thrombospondin-1 deficiency of neonatal platelets might contribute to the relatively impaired response to collagen, and platelet-derived thrombospondin-1 may control distinct collagen-induced platelet responses.
Assuntos
Envelhecimento/fisiologia , Plaquetas/metabolismo , Colágeno/farmacologia , Trombospondina 1/farmacologia , Difosfato de Adenosina/farmacologia , Adolescente , Adulto , Plaquetas/efeitos dos fármacos , Criança , Venenos de Crotalídeos/farmacologia , Exocitose/efeitos dos fármacos , Humanos , Lactente , Recém-Nascido , Lectinas Tipo C , Peptídeos/farmacologia , Ativação Plaquetária/efeitos dos fármacos , Receptores Ativados por Proteinase/metabolismo , Trombospondina 1/químicaAssuntos
Glomerulonefrite Membranoproliferativa/diagnóstico , Injúria Renal Aguda/sangue , Injúria Renal Aguda/etiologia , Idoso , Anticorpos Anticitoplasma de Neutrófilos/sangue , Infecções por Bartonella/sangue , Infecções por Bartonella/complicações , Complemento C3/análise , Complemento C4/análise , Endocardite Bacteriana/sangue , Endocardite Bacteriana/complicações , Glomerulonefrite Membranoproliferativa/sangue , Glomerulonefrite Membranoproliferativa/complicações , Glomerulonefrite Membranoproliferativa/microbiologia , Hematúria/sangue , Hematúria/etiologia , Humanos , MasculinoRESUMO
We describe the case of a 33 year old man with Tricho-Rhino-Phalangeal Syndrome (TRPS) and mitral valve disease. Tricho-Rhino-Phalangeal Syndrome is a rare multisystem disorder. The English literature has no record of any association with mitral valve disease which was a feature of our patient and his father both of whom were suffering from the syndrome. Doctors looking after patients with that condition should be alert to this possible association.
