Salla disease | |
---|---|
Other names | Sialic acid storage disease or Finnish type sialuria [1] |
Sialic acid | |
Specialty | Neurology, endocrinology |
Symptoms | hepatosplenomegaly; hypotonia; failure to thrive; developmental delays; cognitive deficits; seizures; skeletal abnormalities; dysplasia; metaphyses; clubbed feet; abnormally short thigh bones; dysplasia; nystagmus; ataxia. |
Usual onset | Affected infants appear normal at birth but may develop symptoms during the first year of life. |
Duration | Lifelong |
Causes | mutations in the SLC17A5 gene |
Diagnostic method | clinical evaluation and genetic testing |
Prognosis | variable |
Frequency | <1 per 1,000,000 individuals |
Salla disease (SD) or mild Free Sialic Acid Storage Disease (FSASD) is an autosomal recessive [2] lysosomal storage disease characterized by early physical impairment and intellectual disability. Salla disease (also referred to as Finnish-type sialuria, OMIM#604369) was first reported as a lysosomal storage disorder in a family from northern Finland. Salla refers to the area where the affected family resided. It was first described in 1979, [3] after Salla, a municipality in Finnish Lapland and is one of 40 Finnish heritage diseases. The term Salla disease is now used in the literature not only for FSASD cases with the Finnish founder variant in SLC17A5, but also for any mild FSASD cases, independent of the mutation or region of origin. [4]
FSASD (Salla and Infantile Free Sialic Acid Storage Disease) affect males and females in equal numbers. The worldwide prevalence of FSASD is estimated at less than 1 per 1,000,000 individuals. Higher estimated prevalence rates occur in the Salla region of Finland and in other Scandinavian countries.
Affected infants appear normal at birth but may develop symptoms during the first year of life. Individuals with Salla disease may present with nystagmus as well as hypotonia, and may have difficulty coordinating voluntary movements (ataxia), reduced muscle tone and strength, and cognitive impairment. [5] The most severely impaired children do not walk or acquire language, but the typical patient learns to walk and speak and has normal life expectancy. The MRI shows arrested or delayed myelination. [6]
Approximately two-thirds of children with mild FSASD eventually learn to walk. Some degree of speech impairment is usually present. Affected infants may learn single words or small sentences, but this ability may be lost as they age. The ability to produce speech is affected more severely than the ability to understand speech. Affected children exhibit some degree of cognitive impairment as well.[ citation needed ]
FSASD (Salla and Infantile Free Sialic Acid Storage Disease) affect males and females in equal numbers. The worldwide prevalence of FSASD is estimated at less than 1 per 1,000,000 individuals. Higher estimated prevalence rates occur in the Salla region of Finland and in other Scandinavian countries.[ citation needed ]
Approximately ~300 individuals with FSASD have been reported in the literature, of which the majority (> 160 cases) are of Finnish or Swedish ancestry. Individuals with FSASD may go misdiagnosed or undiagnosed, making it difficult to determine the true frequency of the disease in the general population.[ citation needed ]
SD is caused by a mutation in the SLC17A5 gene, located at human chromosome 6q14-15. [2] [7] This gene codes for sialin, a lysosomal membrane protein that transports the charged sugar, N-acetylneuraminic acid (sialic acid), out of lysosomes. The mutation causes sialic acid to build up in the cells.[ citation needed ]
The disease is inherited in an autosomal recessive manner. [2] This means the defective gene responsible for the disorder is located on an autosome (chromosome 6 is an autosome), and two copies of the defective gene (one inherited from each parent) are required in order to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but usually do not experience any signs or symptoms of the disorder.[ citation needed ]
A diagnosis of this disorder can be made by measuring urine to look for elevated levels of free sialic acid. [8] Prenatal testing is also available for known carriers of this disorder.[ citation needed ] The diagnosis is ultimately confirmed by identifying genetic mutation(s) in the SLC17A5 gene by molecular genetic testing. This testing is available on a clinical basis.
There is no cure for Salla disease. Treatment is limited to controlling the symptoms of this disorder. Anti-convulsant medication may control seizure episodes. Physical therapists can assist an affected individual to build muscle strength and coordination.[ citation needed ]
Genetic counseling is recommended for affected individuals and their families.[ citation needed ]
Information on current clinical trials is posted on the Internet at . All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site. [9]
Some individuals with mild FSASD may not develop symptoms until later in childhood when a variety of neurological findings become apparent. These include seizures, involuntary muscles spasms that result in slow, stiff movements of the legs (spasticity), and repetitive, involuntary, writhing movements of the arms and legs (athetosis). Some individuals who previously developed the ability to walk or talk may lose these skills (regression). Some individuals may experience a gradual coarsening of facial features. [ citation needed ]
Gaucher's disease or Gaucher disease (GD) is a genetic disorder in which glucocerebroside accumulates in cells and certain organs. The disorder is characterized by bruising, fatigue, anemia, low blood platelet count and enlargement of the liver and spleen, and is caused by a hereditary deficiency of the enzyme glucocerebrosidase, which acts on glucocerebroside. When the enzyme is defective, glucocerebroside accumulates, particularly in white blood cells and especially in macrophages. Glucocerebroside can collect in the spleen, liver, kidneys, lungs, brain, and bone marrow.
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.
Alpha-mannosidosis is a lysosomal storage disorder, first described by Swedish physician Okerman in 1967. In humans it is known to be caused by an autosomal recessive genetic mutation in the gene MAN2B1, located on chromosome 19, affecting the production of the enzyme alpha-D-mannosidase, resulting in its deficiency. Consequently, if both parents are carriers, there will be a 25% chance with each pregnancy that the defective gene from both parents will be inherited, and the child will develop the disease. There is a two in three chance that unaffected siblings will be carriers. In livestock alpha-mannosidosis is caused by chronic poisoning with swainsonine from locoweed.
Cystinosis is a lysosomal storage disease characterized by the abnormal accumulation of cystine, the oxidized dimer of the amino acid cysteine. It is a genetic disorder that follows an autosomal recessive inheritance pattern. It is a rare autosomal recessive disorder resulting from accumulation of free cystine in lysosomes, eventually leading to intracellular crystal formation throughout the body. Cystinosis is the most common cause of Fanconi syndrome in the pediatric age group. Fanconi syndrome occurs when the function of cells in renal tubules is impaired, leading to abnormal amounts of carbohydrates and amino acids in the urine, excessive urination, and low blood levels of potassium and phosphates.
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.
Sandhoff disease is a lysosomal genetic, lipid storage disorder caused by the inherited deficiency to create functional beta-hexosaminidases A and B. These catabolic enzymes are needed to degrade the neuronal membrane components, ganglioside GM2, its derivative GA2, the glycolipid globoside in visceral tissues, and some oligosaccharides. Accumulation of these metabolites leads to a progressive destruction of the central nervous system and eventually to death. The rare autosomal recessive neurodegenerative disorder is clinically almost indistinguishable from Tay–Sachs disease, another genetic disorder that disrupts beta-hexosaminidases A and S. There are three subsets of Sandhoff disease based on when first symptoms appear: classic infantile, juvenile and adult late onset.
Hereditary inclusion body myopathies (HIBM) are a group of rare genetic disorders which have different symptoms. Generally, they are neuromuscular disorders characterized by muscle weakness developing in young adults. Hereditary inclusion body myopathies comprise both autosomal recessive and autosomal dominant muscle disorders that have a variable expression (phenotype) in individuals, but all share similar structural features in the muscles.
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.
Aceruloplasminemia is a rare autosomal recessive disorder in which the liver can not synthesize the protein ceruloplasmin properly, which is needed to transport copper around the blood. Copper deficiency in the brain results in neurological problems that generally appear in adulthood and worsen over time.
Heřmanský–Pudlák syndrome is an extremely rare autosomal recessive disorder which results in oculocutaneous albinism, bleeding problems due to a platelet abnormality, and storage of an abnormal fat-protein compound. It is thought to affect around 1 in 500,000 people worldwide, with a significantly higher occurrence in Puerto Ricans, with a prevalence of 1 in 1800. Many of the clinical research studies on the disease have been conducted in Puerto Rico.
The GM1 gangliosidoses, usually shortened to GM1, are gangliosidoses caused by mutation in the GLB1 gene resulting in a deficiency of beta-galactosidase. The deficiency causes abnormal storage of acidic lipid materials in cells of the central and peripheral nervous systems, but particularly in the nerve cells, resulting in progressive neurodegeneration. GM1 is a rare lysosomal storage disorder with a prevalence of 1 to every 100,000 to 200,000 live births worldwide, although rates are higher in some regions.
Infantile Refsum disease (IRD) is a rare autosomal recessive congenital peroxisomal biogenesis disorder within the Zellweger spectrum. These are disorders of the peroxisomes that are clinically similar to Zellweger syndrome and associated with mutations in the PEX family of genes. IRD is associated with deficient phytanic acid catabolism, as is adult Refsum disease, but they are different disorders that should not be confused.
Infantile neuroaxonal dystrophy (INAD) is a rare pervasive developmental disorder that primarily affects the nervous system. Individuals with infantile neuroaxonal dystrophy typically do not have any symptoms at birth, but between the ages of about 6 and 18 months they begin to experience delays in acquiring new motor and intellectual skills, such as crawling or beginning to speak. Eventually they lose previously acquired skills.
Sialin, also known as H(+)/nitrate cotransporter and H(+)/sialic acid cotransporter, is a protein which in humans is encoded by the SLC17A5 gene.
Beta-mannosidosis, also called lysosomal beta-mannosidase deficiency, is a disorder of oligosaccharide metabolism caused by decreased activity of the enzyme beta-mannosidase. This enzyme is coded for by the gene MANBA, located at 4q22-25. Beta-mannosidosis is inherited in an autosomal recessive manner. Affected individuals appear normal at birth, and can have a variable clinical presentation. Infantile onset forms show severe neurodegeneration, while some children have intellectual disability. Hearing loss and angiokeratomas are common features of the disease.
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.
Infantile free sialic acid storage disease (ISSD) is a lysosomal storage disease. ISSD occurs when sialic acid is unable to be transported out of the lysosomal membrane and instead accumulates in the tissue, causing free sialic acid to be excreted in the urine. Mutations in the SLC17A5 gene cause all forms of sialic acid storage disease. The SLC17A5 gene is located on the long (q) arm of chromosome 6 between positions 14 and 15. This gene provides instructions for producing a protein called sialin that is located mainly on the membranes of lysosomes, compartments in the cell that digest and recycle materials.
X-linked spinal muscular atrophy type 2, also known as arthrogryposis multiplex congenita X-linked type 1 (AMCX1), is a rare neurological disorder involving death of motor neurons in the anterior horn of spinal cord resulting in generalised muscle wasting (atrophy). The disease is caused by a mutation in UBA1 gene and is passed in an X-linked recessive manner by carrier mothers to affected sons.
Lethal congenital contracture syndrome 1 (LCCS1), also called Multiple contracture syndrome, Finnish type, is an autosomal recessive genetic disorder characterized by total immobility of a fetus, detectable at around the 13th week of pregnancy. LCCS1 invariably leads to prenatal death before the 32nd gestational week. LCCS1 is one of 40 Finnish heritage diseases. It was first described in 1985 and since then, approximately 70 cases have been diagnosed.
Lysosomal acid lipase deficiency is an autosomal recessive inborn error of metabolism that results in the body not producing enough active lysosomal acid lipase (LAL) enzyme. This enzyme plays an important role in breaking down fatty material in the body. Infants, children and adults that have LAL deficiency experience a range of serious health problems. The lack of the LAL enzyme can lead to a build-up of fatty material in a number of body organs including the liver, spleen, gut, in the wall of blood vessels and other important organs.