ELN Foundation and France National Cancer Institute.

SummaryBone involvement is the commonest clinical manifestation of sickle cell disease both in the acute setting such as painful vasoocclusive crises, and as a source of chronic, progressive disability such as avascular necrosis. Management of these problems is often difficult because of the diagnostic imprecision of most laboratory and imaging investigations and because of the lack of evidence for most surgical procedures in sickle cell disease. This review first discusses the acute problems related to bone involvement in sickle cell disease, with particular reference to differentiating infection from infarction, and then describes the long-term effects of sickle cell disease on bone mineral density, growth, and chronic bone and joint damage.

Attachment to the plasma membrane by linkage to a glycosylphosphatidylinositol (GPI) anchor is a mode of protein expression highly conserved from protozoa to mammals. As a clinical entity, deficiency of GPI has been recognized as paroxysmal nocturnal hemoglobinuria, an acquired clonal disorder associated with somatic mutations of the X-linked PIGA gene in hematopoietic cells. We have identified a novel disease characterized by a propensity to venous thrombosis and seizures in which deficiency of GPI is inherited in an autosomal recessive manner. In two unrelated kindreds, a point mutation (c --> g) at position -270 from the start codon of PIGM, a mannosyltransferase-encoding gene, disrupts binding of the transcription factor Sp1 to its cognate promoter motif. This mutation substantially reduces transcription of PIGM and blocks mannosylation of GPI, leading to partial but severe deficiency of GPI. These findings indicate that biosynthesis of GPI is essential to maintain homeostasis of blood coagulation and neurological function.