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ALG1-congenital disorder of glycosylation
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

ALG1-congenital disorder of glycosylation

ALG1-congenital disorder of glycosylation is an inherited condition that impairs the body's ability to process proteins and fats, leading to a wide range of developmental and physical symptoms.

Overview

ALG1-congenital disorder of glycosylation (ALG1-CDG), also known as congenital disorder of glycosylation type Ik, is an inherited disorder with varying signs and symptoms that typically develop during infancy and can affect several body systems.

Symptoms

Individuals with ALG1-CDG often experience a range of health challenges, including:

  • Intellectual disability and delayed development
  • Weak muscle tone (hypotonia)
  • Seizures that can be difficult to treat
  • Movement problems, such as involuntary rhythmic shaking (tremor) or difficulties with movement and balance (ataxia)
  • Blood clotting or bleeding episodes
  • Reduced levels of antibodies (immunoglobulins), particularly IgG, which can make it difficult to fight infections
  • Physical abnormalities, including a small head size (microcephaly), unusual facial features, joint deformities (contractures), long slender fingers and toes (arachnodactyly), or fleshy pads at the tips of fingers and toes
  • Eye problems, such as eyes that do not point in the same direction (strabismus) or involuntary eye movements (nystagmus); rarely, vision loss
  • Less common issues including respiratory problems, reduced sensation in the limbs (peripheral neuropathy), swelling (edema), and gastrointestinal difficulties

While signs and symptoms are often severe, leading to survival only into infancy or childhood, some individuals are more mildly affected and survive into adulthood.

Causes

The condition is caused by mutations in the ALG1 gene. This gene provides instructions for making an enzyme involved in glycosylation, a process where sugar molecules (oligosaccharides) are added to proteins and fats to help them function correctly. Mutations lead to an abnormal enzyme with reduced activity, resulting in incomplete sugar chains and impaired function of various organs and tissues.

Inheritance

This condition is inherited in an autosomal recessive pattern. This means both copies of the gene in each cell have mutations. Parents of an affected individual each carry one copy of the mutated gene but typically do not show signs or symptoms of the condition.

Frequently Asked Questions

Children with ALG1‑CDG often have hypogammaglobulinemia. Regular monitoring of immunoglobulin levels is essential. If IgG falls below protective thresholds, monthly intravenous immunoglobulin (IVIG) replacement can be given to boost immunity and lower infection frequency. Prompt treatment of any bacterial infection with appropriate antibiotics is also critical.
Diagnosis usually starts with clinical suspicion based on developmental delay, hypotonia, seizures, and abnormal facial features. Laboratory screening includes transferrin isoelectric focusing or mass spectrometry to detect abnormal glycosylation patterns. Confirmatory testing is done by sequencing the ALG1 gene to identify pathogenic mutations.
Urgent signs include sudden worsening of seizures, unexplained bruising or bleeding (which may indicate a clotting defect), severe respiratory distress, or a rapid decline in consciousness. Because clotting abnormalities are common, any head trauma or unexplained bleeding should prompt immediate evaluation in an emergency department.
The severity varies widely. Some infants with severe multisystem involvement may not survive beyond early childhood, while milder cases can live into adulthood. Multidisciplinary care—neurology for seizure control, physical therapy for hypotonia, occupational therapy for motor skills, hematology for bleeding disorders, and regular developmental assessments—can maximize functional abilities and reduce complications. Palliative care teams can also help families manage complex medical needs and improve overall quality of life.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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