Which of the following is a membrane receptor defect -

Familial hypercholesterolemia is a receptor disease that is the consequence of a mutation in the gene encoding the receptor for LDL,which is involved in the transpo and metabolism of cholesterol. LDL receptor is situated in the liver cell membrane . Thalasssaemia syndromes are heterogeneous groups of disorders caused by inherited mutations that decrease the synthesis of either alpha globin or beta globin chains that compose adult Hb,HbA leading to tissue hypoxia and red cell hemolysis related to the imbalance in globin chain synthesis. Sickle cell disease is a common hereditary hemoglobinopathy caused by a point mutation in beta globin that promotes the polymerisation of deoxygenated Hb,leading to red cell distoion, hemolytic anaemia, micro vascular obstruction and ischemic tissue damage. Henoch Schonlein purpura is a systemic immune disorder. Results from deposition of immune complexes within the vessels throughout the body and within the glomerular mesangial regions. Ref: Robbins and Cotran Pathologic basis of disease.South Asia Edition volume 19th edition.page no.147,635,638,656