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Condition report · Metabolic

NGLY1 Deficiency (Congenital Disorder of Deglycosylation)

Whole genome sequencing reads the NGLY1 gene for inherited changes that cause NGLY1 deficiency, a condition that affects development, movement, tears, liver function and sweating.

A condition report looks for rare variants known to cause the conditions it covers.

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About this condition

A rare inherited condition in which cells cannot properly recycle certain sugar-tagged proteins, causing developmental delay, a movement disorder, reduced tears and liver problems. It is caused by changes in both copies of the NGLY1 gene.

NGLY1 deficiency is a rare inherited condition in which cells cannot properly remove sugar chains from misfolded proteins, so those proteins are not broken down as they should. Global developmental delay, a movement disorder and low muscle tone usually appear in infancy, and the severity varies widely.

The condition is caused by loss-of-function changes in both copies of NGLY1. Reduced or absent tears, raised liver enzymes in early childhood and low sweating are characteristic, and about half of people develop seizures. Some people also have sleep apnoea or peripheral neuropathy.

The condition is inherited in an autosomal recessive way, and each parent usually carries one changed copy. Care is supportive, with eye lubrication to protect the cornea, monitoring of liver function, seizure treatment and developmental therapies.

The condition we analyse

Autosomal recessive

Caused by loss-of-function changes in both copies of NGLY1, which removes sugar chains from misfolded proteins so they can be broken down. Each parent usually carries one changed copy.

Signs and symptoms

Global developmental delay, a hyperkinetic movement disorder and low muscle tone usually appear in infancy. Reduced or absent tears, raised liver enzymes in early childhood and low sweating are characteristic. About half of people develop seizures, and some may have peripheral neuropathy or sleep problems.

What a diagnosis changes

Care is supportive, with eye lubrication to protect the cornea, monitoring of liver function, seizure treatment and developmental therapies. Genetic counselling and carrier testing of relatives clarify recurrence risk.

Genes analysed

Also known as

CDDG; CDG1V; congenital disorder of deglycosylation; congenital disorder of deglycosylation;CDDG; congenital disorder of glycosylation type IV; NGLY1-CDDG; NGLY1-related congenital disorder of deglycosylation

MONDO:0800044OMIM 615273Orphanet 404454Sources: [1][4][3]

Why whole genome sequencing

NGLY1 deficiency is inherited in a recessive way, so carrier testing matters for relatives. Whole genome sequencing reads the NGLY1 gene in the same test.

Standard screens can miss it

Usual blood tests for congenital disorders of glycosylation do not reliably detect NGLY1 deficiency. Genetic testing that reads the NGLY1 gene is therefore needed, and a diagnosis requires changes in both copies.

Carrier testing for relatives

Each parent usually carries one changed copy, so each child of two carriers has a 1 in 4 chance of being affected. Once the family's changes are known, carrier testing for relatives and prenatal testing in a pregnancy at increased risk are possible.

References

  1. Lam C, Wolfe L, Need A, Shashi V, Enns G, 2018. NGLY1-Related Congenital Disorder of Deglycosylation. GeneReviews
  2. NGLY1 gene. MedlinePlus Genetics
  3. Lehrbach NJ, 2022. NGLY1: insights from Caenorhabditis elegans. Journal of biochemistry
  4. NGLY1-congenital disorder of deglycosylation. MedlinePlus Genetics

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