Mucopolysaccharidoses

Qu'est-ce que Mucopolysaccharidoses?

Mucopolysaccharidoses refers to a group of inherited metabolic disorders. There are 7 specific genetic disorders within this group. The condition is progressive, and symptoms can vary significantly, even among individuals within the same family. Most individuals are diagnosed in either childhood or adolescence.

The Mucopolysaccharidoses group of disorders affects around 1 in 25,000 children a year.

Health conditions related to the syndrome may include heart and respiratory disease and severe sleep apnea. Enlarged organs are also a potential health complication in individuals with the syndrome. Shared characteristics of all Mucopolysaccharidoses include growth and/or developmental delay, coarse facies, skeletal dysplasia, hernia, and corneal clouding.

Syndrome Synonyms:
Mps V, Formerly; Mps5, Formerly Mucopolysaccharidosis Type Is; Mps1-s Mucopolysaccharidosis Type V, Formerly

Quelles sont les causes des changements génétiques Mucopolysaccharidoses?

Individuals with Mucopolysaccharidoses either lack or have malfunctioning lysosomal enzymes. These enzymes are responsible for breaking down glycosaminoglycans, or complex carbohydrates within the body. When they are missing or malfunctioning, it leads to a build of carbohydrates in the cells, blood, brain, and spinal cord, leading to cellular damage.

Most Mucopolysaccharidoses are autosomal recessive disorders. In the case of autosomal dominant inheritance just one parent is the carrier of the gene mutation, and they have a 50% chance of passing it onto each of their children. Syndromes inherited in an autosomal dominant inheritance are caused by just one copy of the gene mutation.

Quels sont les principaux symptômes de Mucopolysaccharidoses?

The main symptoms of Mucopolysaccharidoses may vary between individuals and may also vary in the extent of their severity. The condition is progressive, and most individuals deteriorate over time in terms of their health condition.

Common symptoms in the early stages of diagnosis include frequent colds and growth and developmental delays. Typical facial features include a flat nasal bridge, thick lips, an enlarged mouth, and jaw. Dwarfism, dysplasia, and excess body hair are other possible symptoms.

Possible clinical traits/features:
Limitation of joint mobility, Decreased nerve conduction velocity, Coarse facial features, Everted lower lip vermilion, Obstructive sleep apnea, Sensorineural hearing impairment, Pes cavus, Autosomal recessive inheritance, Short neck, Wide mouth, Sinusitis, Retinal degeneration, Wide nose, Broad face, Abnormal aortic valve morphology, Mucopolysacchariduria, Cerebral palsy, Aortic valve stenosis, Aortic regurgitation, Intellectual disability, Mandibular prognathia, Splenomegaly, Thick lower lip vermilion, Glaucoma, Full cheeks, Genu valgum, Depressed nasal bridge, Hypertonia, Hepatomegaly, Opacification of the corneal stroma, Hemiplegia/hemiparesis

Comment quelqu'un se fait-il tester pour Mucopolysaccharidoses?

The initial testing for Mucopolysaccharidoses may vary between individual can begin with facial analysis screening, through the FDNA Telehealth telegenetics platform, which can identify the key markers of the syndrome and outline the need for further testing. A consultation with a genetic counselor and then a geneticist will follow. 

Based on this clinical consultation with a geneticist, the different options for genetic testing will be shared and consent will be sought for further testing.   

Informations médicales sur Mucopolysaccharidoses

The main problem for the clinical geneticist is not usually the diagnosis. Although it should be noted that mild and severe cases can occur within the same family, there is evidence that in the majority of cases the condition does breed true. Hemizygous males can be diagnosed by analysing amniotic fluid cells (estimating sulphoiduronate sulphatase activity), and amniotic fluid (by thin layer chromatography of mucopolysaccharides), but these are fairly late tests and most patients would want to consider tests on a chorion villus sample. This has been achieved and should be the method of choice. Occasional cases in females have been shown to be due to skewed X chromosome inactivation (Sukegawa et al., 1997, Pina-Aguilar et al., 2013). Nelson et al., (2003) found the incidence in Western Australia to be approximately 1 in 165,000 male live births.
Carrier detection is a greater problem, in that the discrimination between enzyme levels in heterozygotes and normal homozygotes in serum or hairbulbs is not absolute, but gives a probability of being a carrier. About 30% of cases have gene deletions and carrier detection using in situ hybridization has been achieved (Stone and Adinolfi, 1992). Froissart et al., (1997) provided evidence of germline and somatic mosaicism in a female. Other hot spots in the gene for mutations have also been described (Rathman et al., 1996). Timms et al., (1998) reported further mutations and deletions. Inversions, probably caused by recombination between the IDS gene and a pseudogene are also frequent (Lagerstedt., 1997; Bunge et al., 1998). Further mutations were reported by Li et al., (1999) and Vafiadaki et al., (1998).
Chiong et al. (2017) described clinical, biochemical, and molecular features of Hunter syndrome in Philippines. Twenty three males with mean age 11.28 years were included. Age of onset of the symptoms was 1.2 years, whereas mean age at biochemical diagnosis was eight years. The early symptoms included developmental delay, joint restriction, coarse facies, recurrent upper respiratory tract infections, abdominal distention, hernia, and recurrent ear infections. Joint contractures were observed in 69.57% of the cases. Other characteristics included epilepsy (17.3%), hydrocephalus (4.3%), hepatosplenomegaly (39%), airway obstruction (39%), papular rash (26%), kyphoscoliosis (17%), valvular thickness (17%), papilledema (13%), carpal tunnel syndrome (22%), neuropathy (8.7%), and hip dysplasia (4%). Ophthalmologic findings showed error of refraction (52%) and glaucoma, (21.7%). Hearing loss was profound in 17.4%, moderate to profound in 8.7%, moderate in 4.3%, and unclassified in 7.4%. Additional features included hypertrophic tonsils (39%), obstructive sleep apnea (39%), bronchial asthma (34.8%), allergic rhinitis (47.8%), mild valvular regurgitation involving aortic and mitral valves (47.8%), left ventricular dysfunction (13%), left ventricular hypertrophy (8.7%), and dysostosis multiplex (8.7%).

* This information is courtesy of the L M D.
If you find a mistake or would like to contribute additional information, please email us at: [email protected]

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