Hunter syndrome: description, clinical picture
Mucopolysaccharidosis of the second type - Hunter syndrome - is of a rather rare nature, linked to chromosome X. Against the background of pathology, enzyme deficiency is observed. It is accompanied by incomplete destruction and accumulation of glycosaminoglycans (acid mucopolysaccharides) in different tissues. Next, we consider Hunter syndrome in more detail.
Hunter syndrome is found in one case out of 100,000-150,000 newborns. Today in the world there are no more than 2000 such patients. Official statistics for the Russian Federation is missing. Hunter syndrome is included in the category of orphan pathologies. In accordance with the current legislation, the treatment of the disease is carried out at the expense of the regional and federal budgets. In Russia, the ICAO "Hunter-Syndrome" operates. The organization is located in Moscow. Society "Hunter-Syndrome" provides assistance to persons with disabilities and their relatives. The union is charitable.
Causes of pathology
The disease is caused by a mutation of the IDS gene (iduronate sulfatase). It encodes iduronate-2-sulfatase - a lysosomal enzyme. To date, more than 150 variants of gene mutations are known. Due to the linkage with chromosome X, pathology usually appears in boys. Heterozygous women in almost all cases are carriers of the syndrome without clinical signs. However, in practice several times the pathology was manifested in girls. These cases are associated with inactivation of the normal chromosome X or a new mutation. Gene disorders are accompanied by a lack or absence of iduronate-2-sulfatase - the I2S enzyme, partial cleavage and accumulation in the cellular lysosomes of almost all the organs and tissues of heparan sulfate and dermatan sulfate - glycosaminoglycans.
Classification of pathology
Hunter syndrome, the symptoms of which have varying degrees of severity, may be severe. In general, the degree depends on the type of gene mutation. Thus, complex rearrangements and large deletions usually cause it is the heavy form. For this degree of mucopolysaccharidosis (type II A), a rather early manifestation of clinical signs is characteristic. Mostly they begin to be found in children 18-36 months.Early manifestation of pathology differs rapidly progressive course. The child has mental retardation of a pronounced nature, multiple organ failure. The death of patients with severe forms occurs in the second decade of life. Approximately one third of patients suffer from a moderate form of mucopolysaccharidosis (type II B). Signs of pathology in this case manifest in children 3-8, and sometimes 10-13 years. As a rule, the intellect is preserved. Under favorable conditions, the life expectancy of patients can reach 50-60 liters. With a mild form of pathology, patients can quite easily adapt to society, realize themselves quite successfully in the professional sphere. They also have the opportunity to give birth to healthy children.
Newborns with the syndrome look quite healthy. As a rule, the main symptoms begin to appear at the age of 2-4 years. Up to this point, the symptoms are non-specific. In particular, children have recurrent rhinitis, inguinal and umbilical hernia, noisy breathing, hydrocele. Early manifestation characteristic of a pathology is an external change in a child.So, his facial features grow coarser, his nostrils, lips and tongue increase in size, his skin thickens. This is joined by short stature, the head becomes large, the neck is shortened. Also, the development of the disease is accompanied by an anomaly of the dentition. Externally, children suffering from the syndrome are very similar to each other. Other early signs of mucopolysaccharidosis include hoarseness, hepatosplenomegaly, and an increase in the abdomen. Children suffering from pathology are prone to the frequent occurrence of SARS, laryngitis, otitis, pneumonia, tracheitis. Often, patients are diagnosed with chronic diarrhea, obstructive sleep apnea. Due to the deposition of glycosaminoglycans and lipids in the dermis, nodular-papular rash on the skin of the shoulder blades, thighs, and shoulders appears. "Mongolian spots" may form in the lumbosacral area.
Nervous disorders include convulsions, hyperexcitability, delayed speech development, associated hydrocephalus, progressive hearing loss, spastic paraplegia. Also appear violations of the organs of sight. In particular, atypical retinitis pigmentosa, clouding in the cornea. Cardiologic disorders are referred to later signs of the manifestation of pathology.