Mannoside excess?
summary
Mannoside excess? It means that mannoside excess is a cause α- Systemic diseases caused by mannosidase deficiency. The disease is more common in infants and young people. The clinical features are similar to Hurler's syndrome. There is no mucopolysaccharide, but there is an increase of mannose in tissues.
Mannoside excess?
According to the age of onset, the patients with severe mannoside excess and the onset of mannoside in infancy can be called type I or infant type; The patients with mild disease and juvenile onset are called type II or juvenile type. The former usually develops normally at birth, with progressive facial ugliness, huge tongue, flat nose, big ears, wide crevices, large head, large hands and feet, hypotonia of limbs and bradykinesia at about 1 year old, but its degree is not as good as Hurler syndrome. Sternal protuberance, thoracolumbar hunchback, cranial bone thickening, cornea is generally clear, but some patients have lens opacity, some patients have deafness or language disorders, mental retardation at birth. Type II is more than 2 years old, with normal physical and psychomotor development, progressive brain retardation, frequent respiratory tract infection, ugly face, thick eyebrows, widened incisor teeth spacing, protruding jaw, low anterior hairline and mild bilateral deafness (mostly sensory). Some patients may have pancytopenia.
The basic biochemical abnormality of mannosidosis is acid type α- Mannosidase deficiency. The gene was located in 19p13.2-q12. Normally, this enzyme hydrolyzes oligosaccharides α- Bond linked mannosides. Because the disease is acidic α- Mannosidase deficiency, so glycoprotein can not be decomposed, mannose rich oligosaccharides that is deposited in the tissue, mainly in the brain, and excreted with urine. Neurons in the brain are swollen and balloon like, and the deposit material is glycoprotein containing mannose.
According to the age of onset, the patients with severe mannoside excess and the onset of mannoside in infancy can be called type I or infant type; The patients with mild disease and juvenile onset are called type II or juvenile type. The former usually develops normally at birth, with progressive facial ugliness, huge tongue, flat nose, big ears, wide crevices, large head, large hands and feet, hypotonia of limbs and bradykinesia at about 1 year old, but its degree is not as good as Hurler syndrome. Sternal protuberance, thoracolumbar hunchback, cranial bone thickening, cornea is generally clear, but some patients have lens opacity, some patients have deafness or language disorders, mental retardation at birth. Type II is more than 2 years old, with normal physical and psychomotor development, progressive brain retardation, frequent respiratory tract infection, ugly face, thick eyebrows, widened incisor teeth spacing, protruding jaw, low anterior hairline and mild bilateral deafness (mostly sensory). Some patients may have pancytopenia.
matters needing attention
The prevention of genetic diseases, in addition to epidemiological investigation, carrier detection, population genetic monitoring and environmental monitoring, marriage and fertility guidance, efforts to reduce the incidence of genetic diseases in the population and improve the quality of the population, must take effective preventive measures for individuals, To avoid the birth of offspring with genetic diseases (i.e. eugenics) and the occurrence of genetic variation, the usual measures include: premarital examination, genetic counseling, prenatal examination and early treatment of genetic diseases.
