Mucolipidosis IV

Mucolipidosis type IV is a rare lysosomal storage disease characterized by severe psychomotor retardation, visual disturbances and absence of hydrochloric acid in gastric juice or achlorohydria.

Mucolipidoses are a group of diseases affecting lysosomal storage in which the enzymes that act in the lysosome are disrupted. When these enzymes do not function properly, cells are unable to break down certain substances, such as carbohydrates and lipids, resulting in accumulations that induce cell and tissue damage in multiple organs.

Mucolipidoses are classified into 4 types according to the lysosomal enzyme that is affected. In the case of type IV mucolipidosis, it is caused by a deficiency of the enzyme mucolipin-1 which is caused by pathogenic variants in the MCOLN1 gene and especially affects the nervous system producing neurodegeneration.

Type IV mucolipidosis is more frequent in the Ashkenazi Jewish population, in which one in every 100 persons carries a pathogenic variant in MCOLN1.

Symptoms

In type IV mucolipidosis there is severe psychomotor retardation, progressive visual impairment and achlorhydria or deficiency in the production of chlorhydric acid in the stomach. These symptoms usually appear during the first year of life and as the disease progresses, during the second day of life, there is a loss of psychomotor skills leading to patients being unable to walk and presenting with intellectual disability, seizures and visual disturbances including corneal opacity, retinal degeneration and strabismus.

Disease management

There is no cure for this disease and treatment is palliative. Specialized educational and developmental services including speech and physical therapy are available. Use of medications to treat muscle stiffness and seizures. Medical follow-up for digestive and kidney problems. A gastrostomy tube may be inserted in case of persistent feeding problems; lubricating drops and artificial limes may be used; and strabismus may be surgically corrected.

Genes analyzed

MCOLN1

Bibliography

Jezela-Stanek A, Ciara E, Stepien KM. Neuropathophysiology, Genetic Profile, and Clinical Manifestation of Mucolipidosis IV-A Review and Case Series. Int J Mol Sci. 2020 Jun 26;21(12):4564.

Neuropathophysiology, Genetic Profile, and Clinical Manifestation.

Misko A, Grishchuk Y, Goldin E, et al.Mucolipidosis IV. 2005 Jan 28 [updated 2021 Feb 11]. In: Adam MP, Everman DB, Mirzaa GM, Pagon RA, Wallace SE, Bean LJH, Gripp KW, Amemiya A, editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2023.

GeneReviews® [Internet].

Misko A, Wood L, Kiselyov K, et al. Progress in elucidating pathophysiology of mucolipidosis IV. Neurosci Lett. 2021 Jun 11;755:135944.

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