Gene therapy is a medical technology that aims to produce a therapeutic effect through the manipulation of gene expression or through altering the biological properties of living cells.
Osteopetrosis, literally 'stone bone', also known as marble bone disease or Albers-Schönberg disease, is an extremely rare inherited disorder whereby the bones harden, becoming denser, in contrast to more prevalent conditions like osteoporosis, in which the bones become less dense and more brittle, or osteomalacia, in which the bones soften. Osteopetrosis can cause bones to dissolve and break.
Lysosomal storage diseases are a group of over 70 rare inherited metabolic disorders that result from defects in lysosomal function. Lysosomes are sacs of enzymes within cells that digest large molecules and pass the fragments on to other parts of the cell for recycling. This process requires several critical enzymes. If one of these enzymes is defective due to a mutation, the large molecules accumulate within the cell, eventually killing it.
Adenosine deaminase deficiency is a metabolic disorder that causes immunodeficiency. It is caused by mutations in the ADA gene. It accounts for about 10–20% of all cases of autosomal recessive forms of severe combined immunodeficiency (SCID) after excluding disorders related to inbreeding.
Alexander disease is a very rare autosomal dominant leukodystrophy, which are neurological conditions caused by anomalies in the myelin which protects nerve fibers in the brain. The most common type is the infantile form that usually begins during the first two years of life. Symptoms include mental and physical developmental delays, followed by the loss of developmental milestones, an abnormal increase in head size and seizures. The juvenile form of Alexander disease has an onset between the ages of 2 and 13 years. These children may have excessive vomiting, difficulty swallowing and speaking, poor coordination, and loss of motor control. Adult-onset forms of Alexander disease are less common. The symptoms sometimes mimic those of Parkinson's disease or multiple sclerosis, or may present primarily as a psychiatric disorder.
Glycogen storage disease type II(GSD-II), also called Pompe disease, and formerly known as GSD-IIa or Limb–girdle muscular dystrophy2V, is an autosomal recessive metabolic disorder which damages muscle and nerve cells throughout the body. It is caused by an accumulation of glycogen in the lysosome due to deficiency of the lysosomal acid alpha-glucosidase enzyme (GAA). The inability to breakdown glycogen within the lysosomes of cells leads to progressive muscle weakness throughout the body and affects various body tissues, particularly in the heart, skeletal muscles, liver and the nervous system.
Ornithine transcarbamylase deficiency also known as OTC deficiency is the most common urea cycle disorder in humans. Ornithine transcarbamylase, the defective enzyme in this disorder, is the final enzyme in the proximal portion of the urea cycle, responsible for converting carbamoyl phosphate and ornithine into citrulline. OTC deficiency is inherited in an X-linked recessive manner, meaning males are more commonly affected than females.
Krabbe disease (KD) is a rare and often fatal lysosomal storage disease that results in progressive damage to the nervous system. KD involves dysfunctional metabolism of sphingolipids and is inherited in an autosomal recessive pattern. The disease is named after the Danish neurologist Knud Krabbe (1885–1961).
Leukodystrophies are a group of, usually, inherited disorders, characterized by degeneration of the white matter in the brain. The word leukodystrophy comes from the Greek roots leuko, "white", dys, "abnormal" and troph, "growth". The leukodystrophies are caused by imperfect growth or development of the glial cells which produce the myelin sheath, the fatty insulating covering around nerve fibers. Leukodystrophies may be classified as hypomyelinating or demyelinating diseases, respectively, depending on whether the damage is present before birth or occurs after. While all leukodystrophies are the result of genetic mutations, other demyelinating disorders have an autoimmune, infectious, or metabolic etiology.
Batten disease is a fatal disease of the nervous system that typically begins in childhood. Onset of symptoms is usually between 5 and 10 years of age. Often, it is autosomal recessive. It is the common name for a group of disorders called the neuronal ceroid lipofuscinoses (NCLs).
Neuronal ceroid lipofuscinosis is a family of at least eight genetically separate neurodegenerative lysosomal storage diseases that result from excessive accumulation of lipopigments (lipofuscin) in the body's tissues. These lipopigments are made up of fats and proteins. Their name comes from the word stem "lipo-", which is a variation on lipid, and from the term "pigment", used because the substances take on a greenish-yellow color when viewed under an ultraviolet light microscope. These lipofuscin materials build up in neuronal cells and many organs, including the liver, spleen, myocardium, and kidneys.
A lipid storage disorder is any one of a group of inherited metabolic disorders in which harmful amounts of fats or lipids accumulate in some body cells and tissues. People with these disorders either do not produce enough of one of the enzymes needed to metabolize and break down lipids or, they produce enzymes that do not work properly. Over time, the buildup of fats may cause permanent cellular and tissue damage, particularly in the brain, peripheral nervous system, liver, spleen, and bone marrow.
Farber disease is an extremely rare, progressive, autosomal recessive lysosomal storage disease caused by a deficiency of the acid ceramidase enzyme. Acid ceramidase is responsible for breaking down ceramide into sphingosine and fatty acid. When the enzyme is deficient, this leads to an accumulation of fatty material in the lysosomes of the cells, leading to the signs and symptoms of this disorder.
Sphingolipidoses are a class of lipid storage disorders or degenerative storage disorders caused by deficiency of an enzyme that is required for the catabolism of lipids that contain ceramide, also relating to sphingolipid metabolism. The main members of this group are Niemann–Pick disease, Fabry disease, Krabbe disease, Gaucher disease, Tay–Sachs disease and metachromatic leukodystrophy. They are generally inherited in an autosomal recessive fashion, but notably Fabry disease is X-linked recessive. Taken together, sphingolipidoses have an incidence of approximately 1 in 10,000, but substantially more in certain populations such as Ashkenazi Jews. Enzyme replacement therapy is available to treat mainly Fabry disease and Gaucher disease, and people with these types of sphingolipidoses may live well into adulthood. The other types are generally fatal by age 1 to 5 years for infantile forms, but progression may be mild for juvenile- or adult-onset forms.
Arylsulfatase A is an enzyme that breaks down sulfatides, namely cerebroside 3-sulfate into cerebroside and sulfate. In humans, arylsulfatase A is encoded by the ARSA gene.
Galactosialidosis, also known as neuraminidase deficiency with beta-galactosidase deficiency, is a genetic lysosomal storage disease. It is caused by a mutation in the CTSA gene which leads to a deficiency of enzymes β-galactosidase and neuraminidase. This deficiency inhibits the lysosomes of cells from functioning properly, resulting in the accumulation of toxic matter within the cell. Hallmark symptoms include abnormal spinal structure, vision problems, coarse facial features, hearing impairment, and intellectual disability. Because galactosialidosis involves the lysosomes of all cells, it can affect various areas of the body, including the brain, eyes, bones, and muscles. Depending on the patient's age at the onset of symptoms, the disease consists of three subtypes: early infantile, late infantile, and juvenile/adult. This condition is considered rare, with most cases having been in the juvenile/adult group of patients.
Hugo Wolfgang Moser (1924–2007) was a Swiss-born American research scientist and director of the Neurogenetics Research Center at the Kennedy Krieger Institute. Moser was also University Professor of Neurology and Pediatrics at Johns Hopkins University. His research on peroxisomal disorders achieved international recognition.
Metazym is an experimental recombinant enzyme that was studied in patients with late infantile metachromatic leukodystrophy, but found to be ineffective under the conditions of that trial. A subsequent clinical trial is ongoing. The drug became a source of controversy when a family attempted to purchase the drug for their child before it was approved. Jonckheere, Kingma, Eyskens, Bordon, & Jansen (2023) highlight the shift towards the need for newborn screening for metachromatic leukodystrophy as it allows for improved early detection and timely treatment as well.
CDKL5 deficiency disorder (CDD) is a rare genetic disorder caused by pathogenic variants in the gene CDKL5.
Atidarsagene autotemcel, sold under the brand name Libmeldy among others, is a gene therapy treatment for metachromatic leukodystrophy developed by Orchard Therapeutics. It contains an autologous CD34⁺ cell enriched population that contains haematopoietic stem and progenitor cells transduced using a lentiviral vector encoding the human arylsulfatase A (ARSA) gene.
