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Mucolipidosis IV.

Source

GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2017.
2005 Jan 28 [updated 2015 Jul 30].

Author information

1
Director, Institute of Metabolic Disease, Baylor Research Institute, Dallas, Texas
2
MGH Center for Human Genetic Research / Harvard Medical School, Boston, Massachusetts
3
Section on Molecular Neurogenetics, Medical Genetics Branch, National Human Genome Research Institute, National Institutes of Health, Bethesda, Maryland

Excerpt

CLINICAL CHARACTERISTICS:

Mucolipidosis IV is characterized by severe psychomotor delay evident by the end of the first year of life and slowly progressive visual impairment during the first decade as a result of a combination of corneal clouding and retinal degeneration. By the end of the first decade of life and certainly by their early teens, all individuals with typical mucolipidosis IV have severe visual impairment as a result of retinal degeneration. Neurodegeneration is thought to occur in no more than 15% of individuals. About 5% of individuals have atypical mucolipidosis IV, often manifest as less severe psychomotor retardation and/or eye findings. Although in the past, mucolipidosis IV was considered an Ashkenazi Jewish disease, currently most affected individuals are non-Ashkenazi Jewish.

DIAGNOSIS/TESTING:

Mucolipidosis IV is suspected in individuals with typical clinical findings and elevated plasma gastrin concentration or polymorphic lysosomal inclusions in skin or conjunctival biopsy. Identification of biallelic pathogenic variants in MCOLN1 confirms the diagnosis. The two variants, c.406-2A>G and 6.4 kb del (also known as g.511_6943del), account for 95% of pathogenic variants in individuals of Ashkenazi Jewish heritage.

MANAGEMENT:

Treatment of manifestations: Speech therapy; physical therapy for spasticity and ataxia; ankle-foot orthotics (AFOs) as needed; antiepileptic drugs as needed; topical lubricating eye drops, artificial tears, gels, or ointments for ocular irritation; surgical correction of strabismus; high-contrast black and white materials for those with visual impairment. Prevention of secondary complications: Physical therapy to prevent permanent joint contractures; oral iron to prevent iron deficiency anemia from poor absorption of dietary iron.

GENETIC COUNSELING:

Mucolipidosis IV is inherited in an autosomal recessive manner. At conception, each sib of an affected individual has a 25% chance of being affected, a 50% chance of being an asymptomatic carrier, and a 25% chance of being unaffected and not a carrier. Carrier testing for at-risk relatives and prenatal testing for pregnancies at increased risk are possible for families in which both MCOLN1 pathogenic variants have been identified.

Copyright © 1993-2017, University of Washington, Seattle. GeneReviews is a registered trademark of the University of Washington, Seattle. All rights reserved.

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