About ganglioside sialidase deficiency

What is ganglioside sialidase deficiency?

Mucolipidosis IV is a rare inherited metabolic disorder believed to be characterized by a deficiency of transport channel receptor protein, based upon the recent discovery of the Mucolipidosis IV gene. This deficiency may lead to the accumulation of certain fatty substances (mucolipids) and certain complex carbohydrates (mucopolysaccharides) within the cells of many tissues of the body.

Mucolipidosis IV is characterized by mental retardation; severe impairment in the acquisition of skills requiring the coordination of muscular and mental activities (psychomotor retardation); diminished muscle tone (hypotonia); clouding (opacity) of the clear portion of the eyes through which light passes (cornea); and/or degeneration of the nerve-rich membrane lining the eyes (retinal degeneration). Mucolipidosis IV is thought to be inherited as an autosomal recessive genetic trait.

What are the symptoms for ganglioside sialidase deficiency?

Puffy eyelids symptom was found in the ganglioside sialidase deficiency condition

The severe form of the disease is called typical mucolipidosis IV, and the mild form is called atypical mucolipidosis IV. Approximately 95 percent of individuals diagnosed with this condition have the severe form.

The symptoms and physical findings associated with mucolipidosis IV are usually apparent within three to eight months following birth. The first recognized symptoms are usually clouding (opacity) of the cornea and eye movement abnormalities. In some cases, these symptoms may be overlooked until three to five years of age.

Most affected infants exhibit hypotonia, moderate to severe intellectual disability, delays in reaching developmental milestones, and/or significant psychomotor retardation.

In addition, individuals with mucolipidosis IV may have abnormalities affecting the eyes including crossed eyes (strabismus), puffy eyelids, degeneration of the nerve-rich membrane lining the eyes (retina), and/or visual impairment (amblyopia) in an eye that appears structurally normal. In some cases, such Eye abnormalities may result in an abnormal sensitivity to light (photophobia) and/or nearsightedness (myopia).

Individuals with mucolipidosis IV develop iron deficiency anemia because their stomachs do not secrete acid. They do not have enlarged livers or spleens, skeletal involvement, or mucopolysaccharides in the urine.

Patients exhibit accumulation of certain fatty substances (lipids) and certain complex carbohydrates (mucopolysaccharides) within the cells of many tissues of the body. Those appear as large vacuoles and fluorescent vesicles in patient cells.

What are the causes for ganglioside sialidase deficiency?

Mucolipidosis IV is inherited as an autosomal recessive genetic trait. The responsible gene has been isolated and its protein-product, as well as its chromosomal location, determined. The gene, designated MCOLN1, has been tracked to 19p13.3-p13.2 where it encodes for the mucolipin-1 protein. Mutations in this gene result in a deficiency of transport channel receptor protein. The exact function of this protein is still unknown. The effect of mutations on patient and animal model cells indicates a loss of regulation on intracellular traffic which eventually affects various tissue functions.

Chromosomes are found in the nucleus of all body cells. They carry the genetic characteristics of each individual. Pairs of human chromosomes are numbered from 1 through 22, with an unequal 23rd pair of X and Y chromosomes for males and two X chromosomes for females. Each chromosome has a short arm designated as p and a long arm identified by the letter q. Chromosomes are further subdivided into bands that are numbered. For example, chromosome 11p15.4 refers to band 15.4 on the short arm of chromosome 11.

Recessive genetic disorders occur when an individual inherits two copies of an abnormal gene for the same trait, one from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease but usually will not show symptoms. The risk for two carrier parents to both pass the defective gene and have an affected child is 25% with each pregnancy. The risk to have a child who is a carrier like the parents is 50% with each pregnancy. The chance for a child to receive normal genes from both parents and be genetically normal for that particular trait is 25%. The risk is the same for males and females.

All individuals carry 4-5 abnormal genes. Parents who are close relatives (consanguineous) have a higher chance than unrelated parents to both carry the same abnormal gene, which increases the risk to have children with a recessive genetic disorder.

What are the treatments for ganglioside sialidase deficiency?

Treatment of mucolipidosis IV is symptomatic and supportive. Symptoms associated with clouding of the corneas may be treated by the use of contact lenses and/or artificial tears. Intense physical, occupational and speech therapy are also of benefit. Iron replacement is utilized for those with anemia.

Genetic counseling is recommended for affected individuals and their families.

Is there a cure/medications for ganglioside sialidase deficiency?

Ganglioside sialidase deficiency is also known as Sialoglycosphingolipids/ Mucolipidosis IV.
They carry one or more than one sialic residue. This is a very rare metabolic disorder.
It may arise due to a deficiency of transport channel receptor protein. If this disease becomes severe, it is called typical mucolipidosis IV; if it is mild and not that severe, it is called atypical mucolipidosis IV.

  • Medications and treatments of mucolipidosis IV are based on symptoms.
  • But there is no specific treatment for this deficiency.
  • If there is clouding of corneas, then this can be treated by using contact lenses or artificial tears.
  • Various therapies like Intense physical, occupational, speech therapy, enzyme replacement therapy, substrate reduction therapy, and gene therapy can also benefit in curing the ganglioside sialidase deficiency.
  • Physical therapy can help in improving motor function that mainly focuses on spasticity and ataxia.
  • If one is anemic because of poor nutrient absorption by the stomach lining, then iron replacement is utilized. Even genetic counseling is held for the one suffering from this or for their family.
  • Normally, your gastrin levels must range from 0-200pg/ml, but patients suffering from this deficiency have gastrin levels in the range 400-4100 pg/ml. So, measuring blood gastrin levels can be considered useful for diagnosing mucolipidosis IV and is also cost-effective.
  • Skin biopsies are also done.
  • There arises visual impairment, and this problem can be solved by corneal and conjunctival transplantation.
  • Despite all these treatments, unfortunately, ganglioside sialidase deficiency cannot be cured.

Clouding (opacity) of the cornea and eye movement abnormalities,Crossed eyes (strabismus),Puffy eyelids, degeneration of the nerve-rich membrane lining the eyes (retina),Visual impairment (amblyopia)
Hypotonia,Moderate to severe intellectual disability,Delays in reaching developmental milestones,Significant psychomotor retardation
Contact lenses,Artificial tears

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