Inborn Errors of Metabolism and Osteopetrosis

Inborn errors of metabolism (IEM) comprise a large group of inherited disease, some of which are disorders of lysosomal, peroxisomal, or mitochondrial function, and only some can be improved following HCT. The mechanism of action varies between the different metabolic disorders. In the lysosomal disorders, healthy donor cells deliver the enzyme (secretion) to residual enzyme-deficient host cells. This is a changing area of medicine, in which autologous stem cell gene therapy is changing BMT practice, and this is likely to accelerate in the immediate future. Osteopetrosis is a disorder of bone remodelling. The defect usually lies in the osteoclast, which is involved in bone metabolism, and is a specialized tissue macrophage. HCT restores competent tissue osteoclasts and therefore corrects the disease.