Autosomal dominant leukodystrophy with autonomic disease | |
---|---|
Other names | Autosomal dominant adult-onset demyelinating leukodystrophy, ADLD, Adult-onset autosomal dominant demyelinating leukodystrophy, Adult-onset autosomal dominant leukodystrophy, Leukodystrophy, demyelinating, adult-onset, autosomal dominant, Pelizaeus-Merzbacher disease, autosomal dominant or late-onset type, Multiple sclerosis-like disorder [1] |
Specialty | Medical genetics |
Symptoms | Cognitive deficits, ataxia, and dysfunctions of the autonomic system |
Complications | Walking difficulties |
Usual onset | Adulthood |
Duration | Lifelong |
Causes | Genetic mutation |
Diagnostic method | Genetic testing |
Differential diagnosis | Multiple sclerosis |
Prevention | none |
Prognosis | Bad, but quality of life can be improved with treatment |
Frequency | rare, at least 70 people on Earth have been diagnosed with the condition |
Deaths | Inevitable in patients with this condition |
Autosomal dominant leukodystrophy with autonomic disease is a rare neurological condition of genetic origin which is characterized by gradual demyelination of the central nervous system which results in various impairments, including ataxia, mild cognitive disability and autonomic dysfunction. [2] [3] [4] It is part of a group of disorders called "leukodystrophies". [5] [6]
Unlike other leukodystrophy syndromes, whose typical age of onset is during childhood, individuals with this condition typically start showing symptoms between their early 40s and late 50s, once they appear, they slowly progress in severity and new symptoms start appearing. [7]
These symptoms first start out with dysfunctions of the autonomic nervous system which result in symptoms such as abnormal functioning of both the bladder and bowel, recurrent blood pressure drops whenever patients stand up, and male erectile dysfunction. [8] [9] [10]
Rarely, anhidrosis might also occur alongside these symptoms. [9] [8] [11] [10]
After these symptoms start, movement impairments develop; they start off at the legs but then progress and move to the arms and the face, these impairments include either muscular spasticity or weakness, intention tremors, ataxia, dysmetria, and dysdiadochokinesis. [9] [8] [11] [10]
In some individuals, progressive dementia is present. [8] [9] [11]
There are various complications associated with the symptoms that ADLD causes.
Due to the ataxia and it's associated coordination impairments, people might have difficulties with movements such as walking by themselves. [12]
Treatment is focused on the symptoms themselves
The ataxic movement impairments can be treated with walking support systems such as canes or wheelchairs, physical therapy, and speech therapy. [13]
This condition is diagnosed mainly through MRIs [14] [15] and genetic testing of the LMNB gene and the areas surrounding it, [16] although symptom examination is also important for the diagnosis. [17]
This condition is caused by a duplication of the LMNB1 gene, this gene takes part in the production of the lamin B1 protein, which is essential for determining the nucleus' shape within the cells, the replication of DNA, and the way certain genes express themselves. [18] [19] [20] [21] [22] [23] [24]
When the gene is duplicated (as seen in patients with ADLD), there is an excess of lamin B1 protein, this leads to the underexpression of genes that are important for the production of myelin and an increased hardening of the nuclear envelope, which results in a progressive reduction of myelin production and maintenance as one ages. [18]
Like the name of the condition implies, this condition is inherited following an autosomal dominant pattern, which means that only one copy of a certain mutation (in this case, the duplication of the LMNB1 gene) is needed for a trait or disorder to be expressed, in familial cases, offspring have a 1 in 2, or 50% chance of inheriting a copy of said mutation from one of their affected parents. [18]
Although very rarely, this disorder can be caused by deletions near the LMNB1 gene, only one such family has been described in medical literature: they had a deletion upstream the same gene. [25]
In patients with the condition, demyelination (that is, a loss of myelin) starts occurring in both the brain and the spinal cord years before symptoms show up, this abnormality has been identified to be a contributing factor to the development of the first symptoms individuals with this condition show during the early stages of it. [8]
In a 2018 study done by Naomi Mezaki and 18 other colleagues, it was found that ADLD patients with a deletion near the LMNB1 gene (2 patients from a single family) started showing symptoms at an earlier age, had less autonomic dysfunctions and had more noticeable cognitive deficits than other ADLD patients with duplication of the LMNB1 gene (4 patients from 3 families). [26]
This condition is progressive and fatal. [27]
While the quality of life might be improved with treatment, the life expectancy can't be improved easily: individuals diagnosed with ADLD typically live for another 10 to 20 years after their diagnosis before their death. [28] [29]
At least 70 cases from 35 families around the world have been described in medical literature, [30] most of these were from families of Caucasian descent. [31]
This condition was first discovered in 1964 by E Zerbin-Rüdin et al. when they described (what they thought to be) a familial autosomal dominant variant of Pelizaeus-Merzbacher disease with onset in adulthood. [32]
In 2006, Padiath et al. found the LMNB1 duplication involved in ADLD in 4 families, of which 1 was previously described in medical literature. Haplotype studies revealed that the family mentioned beforehand and another Irish-American family shared a common ancestor. The lamin B1 protein was found to be overly expressed in brain tissues of family members affected with ADLD. [33]
Pelizaeus–Merzbacher disease is an X-linked neurological disorder that damages oligodendrocytes in the central nervous system. It is caused by mutations in proteolipid protein 1 (PLP1), a major myelin protein. It is characterized by a decrease in the amount of insulating myelin surrounding the nerves (hypomyelination) and belongs to a group of genetic diseases referred to as leukodystrophies.
Hereditary spastic paraplegia (HSP) is a group of inherited diseases whose main feature is a progressive gait disorder. The disease presents with progressive stiffness (spasticity) and contraction in the lower limbs. HSP is also known as hereditary spastic paraparesis, familial spastic paraplegia, French settlement disease, Strumpell disease, or Strumpell-Lorrain disease. The symptoms are a result of dysfunction of long axons in the spinal cord. The affected cells are the primary motor neurons; therefore, the disease is an upper motor neuron disease. HSP is not a form of cerebral palsy even though it physically may appear and behave much the same as spastic diplegia. The origin of HSP is different from cerebral palsy. Despite this, some of the same anti-spasticity medications used in spastic cerebral palsy are sometimes used to treat HSP symptoms.
A demyelinating disease refers to any disease affecting the nervous system where the myelin sheath surrounding neurons is damaged. This damage disrupts the transmission of signals through the affected nerves, resulting in a decrease in their conduction ability. Consequently, this reduction in conduction can lead to deficiencies in sensation, movement, cognition, or other functions depending on the nerves affected.
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.
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.
Metachromatic leukodystrophy (MLD) is a lysosomal storage disease which is commonly listed in the family of leukodystrophies as well as among the sphingolipidoses as it affects the metabolism of sphingolipids. Leukodystrophies affect the growth and/or development of myelin, the fatty covering which acts as an insulator around nerve fibers throughout the central and peripheral nervous systems. MLD involves cerebroside sulfate accumulation. Metachromatic leukodystrophy, like most enzyme deficiencies, has an autosomal recessive inheritance pattern.
Spinocerebellar ataxia (SCA) is a progressive, degenerative, genetic disease with multiple types, each of which could be considered a neurological condition in its own right. An estimated 150,000 people in the United States have a diagnosis of spinocerebellar ataxia at any given time. SCA is hereditary, progressive, degenerative, and often fatal. There is no known effective treatment or cure. SCA can affect anyone of any age. The disease is caused by either a recessive or dominant gene. In many cases people are not aware that they carry a relevant gene until they have children who begin to show signs of having the disorder.
Laminopathies are a group of rare genetic disorders caused by mutations in genes encoding proteins of the nuclear lamina. Since the first reports of laminopathies in the late 1990s, increased research efforts have started to uncover the vital role of nuclear envelope proteins in cell and tissue integrity in animals. Laminopathies are a group of degenerative diseases, other disorders associated with inner nuclear membrane proteins are known as nuclear envelopathies.
Leukoencephalopathy with vanishing white matter is an autosomal recessive neurological disease. The cause of the disease are mutations in any of the 5 genes encoding subunits of the translation initiation factor eIF2B: EIF2B1, EIF2B2, EIF2B3, EIF2B4, or EIF2B5. The disease belongs to a family of conditions called the Leukodystrophies.
Lamin-B1 is a protein that in humans is encoded by the LMNB1 gene.
Leukoencephalopathy with neuroaxonal spheroids (LENAS), also known as adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP), hereditary diffuse leukoencephalopathy with spheroids (HDLS) and pigmentary orthochromatic leukodystrophy (POLD) is an extremely rare kind of leukoencephalopathy and is classified as a neurodegenerative disease. LENAS is a cause of severe and subacute dementia that results from damage to certain areas of the brain. This damage is to a type of brain tissue called white matter and axon damage due to swellings which are termed spheroids.
Megalencephalic leukoencephalopathy with subcortical cysts is a form of hereditary CNS demyelinating disease. It belongs to a group of disorders called leukodystrophies. It is characterized by early-onset enlargement of the head (macrocephaly) as well as delayed-onset neurological deterioration to include spasticity, epilepsy, and lack of muscular coordination. MLC does not appear to be a disease that is fatal at birth or early in life despite its symptoms, although the number of patients throughout history known to have the disease is fairly limited.
Hereditary neuropathy with liability to pressure palsy (HNPP) is a peripheral neuropathy, a condition that affects the nerves. Pressure on the nerves can cause tingling sensations, numbness, pain, weakness, muscle atrophy and even paralysis of the affected area. In normal individuals, these symptoms disappear quickly, but in sufferers of HNPP even a short period of pressure can cause the symptoms to occur. Palsies can last from minutes or days to weeks or even months.
Hereditary diffuse leukoencephalopathy with spheroids (HDLS) is a rare adult onset autosomal dominant disorder characterized by cerebral white matter degeneration with demyelination and axonal spheroids leading to progressive cognitive and motor dysfunction. Spheroids are axonal swellings with discontinuous or absence of myelin sheaths. It is believed that the disease arises from primary microglial dysfunction that leads to secondary disruption of axonal integrity, neuroaxonal damage, and focal axonal spheroids leading to demyelination. Spheroids in HDLS resemble to some extent those produced by shear stress in a closed head injury with damage to axons, causing them to swell due to blockage of axoplasmic transport. In addition to trauma, axonal spheroids can be found in aged brain, stroke, and in other degenerative diseases. In HDLS, it is uncertain whether demyelination occurs prior to the axonal spheroids or what triggers neurodegeneration after apparently normal brain and white matter development, although genetic deficits suggest that demyelination and axonal pathology may be secondary to microglial dysfunction. The clinical syndrome in patients with HDLS is not specific and it can be mistaken for Alzheimer's disease, frontotemporal dementia, atypical Parkinsonism, multiple sclerosis, or corticobasal degeneration.
Roussy–Lévy syndrome, also known as Roussy–Lévy areflexic dystasia, is a rare disorder of humans that results in progressive muscle wasting. It is caused by mutation the s that code for proteins necessary for the functioning of the myelin sheath of the, affecting the conductance of nerve signals and resulting in loss of muscles' ability to move.
Autosomal dominant cerebellar ataxia (ADCA) is a form of spinocerebellar ataxia inherited in an autosomal dominant manner. ADCA is a genetically inherited condition that causes deterioration of the nervous system leading to disorder and a decrease or loss of function to regions of the body.
Ying-Hui Fu is a Taiwanese-American biologist and human geneticist who has made important contributions to understanding the genetics of many neurological disorders. Her chief discoveries include describing Mendelian sleep phenotypes, identifying causative genes and mutations for circadian rhythm disorders, and characterizing genetic forms of demyelinating degenerative disorders. Fu is currently a professor of neurology at the University of California, San Francisco. She was elected to the US National Academy of Sciences in 2018.
Louis Ptáček is an American neurologist and professor who contributed greatly to the field of genetics and neuroscience. He was also an HHMI investigator from 1997 to 2018. His chief areas of research include the understanding of inherited Mendelian disorders and circadian rhythm genes. Currently, Ptáček is a neurology professor and a director of the Division of Neurogenetics in University of California, San Francisco, School of Medicine. His current investigations primarily focus on extensive clinical studies in families with hereditary disorders, which include identifying and characterizing the genes responsible for neurological variations.
Autosomal dominant cerebellar ataxia, deafness, and narcolepsy (ADCADN) is a rare progressive genetic disorder that primarily affects the nervous system and is characterized by sensorineural hearing loss, narcolepsy with cataplexy, and dementia later in life. People with this disorder usually start showing symptoms when they are in their early-mid adulthoods. It is a type of autosomal dominant cerebellar ataxia.
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