Defining the intensity of conditioning regimens: working definitions.

Lysosomal storage diseases (LSDs) are a group of over 70 diseases that are characterized by lysosomal dysfunction, most of which are inherited as autosomal recessive traits. These disorders are individually rare but collectively affect 1 in 5,000 live births. LSDs typically present in infancy and childhood, although adult-onset forms also occur. Most LSDs have a progressive neurodegenerative clinical course, although symptoms in other organ systems are frequent. LSD-associated genes encode different lysosomal proteins, including lysosomal enzymes and lysosomal membrane proteins. The lysosome is the key cellular hub for macromolecule catabolism, recycling and signalling, and defects that impair any of these functions cause the accumulation of undigested or partially digested macromolecules in lysosomes (that is, 'storage') or impair the transport of molecules, which can result in cellular damage. Consequently, the cellular pathogenesis of these diseases is complex and is currently incompletely understood. Several LSDs can be treated with approved, disease-specific therapies that are mostly based on enzyme replacement. However, small-molecule therapies, including substrate reduction and chaperone therapies, have also been developed and are approved for some LSDs, whereas gene therapy and genome editing are at advanced preclinical stages and, for a few disorders, have already progressed to the clinic.

Lysosomal storage diseases

conclusions Cord blood from unrelated donors appears to be an excellent source of stem cells for transplantation in patients with Hurler’s syndrome. Sustained engraftment can be achieved without total-body irradiation. Cord-blood transplantation favorably altered the natural history of Hurler’s syndrome and thus may be important to consider in young children with this form of the disease.

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Cord-blood transplants from unrelated donors in patients with Hurler's syndrome.

OBJECTIVE. Disease management for mucopolysaccharidosis type I has been inconsistent because of disease rarity (∼1 case per 100000 live births), phenotypic heterogeneity, and limited therapeutic options. The availability of hematopoietic stem cell transplantation and the recent introduction of enzyme replacement therapy for mucopolysaccharidosis I necessitate the establishment of system-specific management guidelines for this condition. METHODS. Twelve international experts on mucopolysaccharidosis I met in January 2003 to draft management and treatment guidelines for mucopolysaccharidosis I. Initial guidelines were revised and updated in 2008, on the basis of additional clinical data and therapeutic advances. Recommendations are based on our extensive clinical experience and a review of the literature. RESULTS.All patients with mucopolysaccharidosis I should receive a comprehensive baseline evaluation, including neurologic, ophthalmologic, auditory, cardiac, respiratory, gastrointestinal, and musculoskeletal assessments, and should be monitored every 6 to 12 months with individualized specialty assessments, to monitor disease progression and effects of intervention. Patients are best treated by a multidisciplinary team. Treatments consist of palliative/supportive care, hematopoietic stem cell transplantation, and enzyme replacement therapy. The patient9s age (>2 years or ≤2 years), predicted phenotype, and developmental quotient help define the risk/benefit profile for hematopoietic stem cell transplantation (higher risk but can preserve central nervous system function) versus enzyme replacement therapy (low risk but cannot cross the blood-brain barrier). CONCLUSION. We anticipate that provision of a standard of care for the treatment of patients with mucopolysaccharidosis I will optimize clinical outcomes and patients9 quality of life.

Mucopolysaccharidosis I: management and treatment guidelines.

Data from 932 patients with leukemia who received bone marrow transplants were analyzed to determine factors associated with an increased risk of developing interstitial pneumonitis. Interstitial pneumonitis developed in 268 patients for a 2-year actuarial incidence of 35 +/- 4% (SD) and with a mortality rate of 24%. Six factors were associated with an increased risk: use of methotrexate rather than cyclosporine after transplantation (relative risk, 2.3; p less than 0.0002); older age (relative risk, 2.1; p less than 0.0001); presence of severe graft-versus-host disease (relative risk, 1.9; p less than 0.003); long interval from diagnosis to transplantation (relative risk, 1.6; p less than 0.002); performance ratings before transplantation of less than 100% (relative risk, 2.1; p less than 0.0001); and high dose-rates of irradiation in patients given methotrexate after transplantation (relative risk, 3.2; p less than 0.03). The risk of developing interstitial pneumonitis ranged from 8% in patients with none of these adverse risk factors to 94% in patients with all six. These findings may help to identify patients at high risk for this complication.

Interstitial pneumonitis after bone marrow transplantation. Assessment of risk factors.

A one-year-old boy with type I H mucopoly saccharidosis (Hurler's disease) was given a bone-marrow transplant (BMT) from his mother in an attempt to replace the deficient enzyme, alpha-L-iduronidase (iduronidase). There is definite evidence of engraftment, the enzyme activity of the recipient's leucocytes reaching heterozygote levels within 37 days of the BMT. Graft-versus-host disease (GVHD) developed but was partially controlled by steroids. From 3-4 months after graft until the present (13 months after the graft) iduronidase activity has been present in the serum and the urine and there has been evidence of considerable degradation of glycosaminoglycans excreted in the urine. The hepatosplenomegaly has disappeared, corneal clouding has cleared, and deterioration in the child's development seems to have been arrested.

Reversal of clinical features of hurler's disease and biochemical improvement after treatment by bone marrow transplantation

Twenty patients have undergone bone marrow transplantation for acute lymphoblastic leukaemia (ALL). Eighteen patients were in complete remission and two had less than 10% leukaemic blasts in the marrow aspirate in the week prior to transplantation. Eighteen patients were grafted from HLA/MLC compatible siblings. One identical twin and one fully compatible parent were also used as donors. Two patients died of graft-versus-host disease and one of radiation-induced pneumonitis. Four have subsequently relapsed. Thirteen patients remain well and in remission from 202 to 1126 d post transplantation. These results show that morbidity and mortality from the bone marrow transplantation procedure is low. However, the major obstacle to permanent success in marrow transplantation of patients with ALL is recurrence of the disease (35% actuarial disease free survival at 1126 d).

Tessa Rogers

Papers

Reversal of clinical features of hurler's disease and biochemical improvement after treatment by bone marrow transplantation

Bone marrow transplantation for acute lymphoblastic leukaemia.

The Transitional Emergency Nurse Practitioner role: Implementation study and preliminary evaluation

Introducing a new collaborative model of practice: Embracing the transitional nurse practitioner role