HomeGeneticsConditionBeta-mannosidosis
Back to Condition
Beta-mannosidosis
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

Beta-mannosidosis

Beta-mannosidosis is a very rare inherited disorder that impairs the body's ability to process certain sugar molecules, leading to a wide range of symptoms including intellectual disability, neurological issues, and distinctive physical features.

Overview

Beta-mannosidosis is a rare inherited disorder affecting the way certain sugar molecules are processed in the body.

Signs and symptoms of beta-mannosidosis vary widely in severity, and the age of onset ranges from infancy to adulthood. Almost all individuals with beta-mannosidosis experience intellectual disability, and some have delayed motor development and seizures. Affected individuals may be prone to depression or have behavioral problems such as hyperactivity, impulsivity or aggression. People with beta-mannosidosis are often extremely introverted.

People with beta-mannosidosis may experience an increased risk of respiratory and ear infections, hearing loss, speech impairment, swallowing difficulties, poor muscle tone (hypotonia), and reduced sensation or other nervous system abnormalities in the extremities (peripheral neuropathy). They may also exhibit distinctive facial features and clusters of enlarged blood vessels forming small, dark red spots on the skin (angiokeratomas).

Frequency

Beta-mannosidosis is believed to be a very rare disorder. It is difficult to determine the specific incidence of beta-mannosidosis, because people with mild or non-specific symptoms may never be diagnosed.

Causes

Variants (also known as mutations) in the MANBA gene cause beta-mannosidosis. The MANBA gene provides instructions for making the enzyme beta-mannosidase. This enzyme works in the lysosomes, which are compartments that digest and recycle materials in the cell. Within lysosomes, the enzyme helps break down complexes of sugar molecules (oligosaccharides) attached to proteins (glycoproteins). Beta-mannosidase is involved in the last step of this process, helping to break down complexes of two sugar molecules (disaccharides) containing a sugar molecule called mannose.

Variants in the MANBA gene interfere with the ability of the beta-mannosidase enzyme to perform its role in breaking down mannose-containing disaccharides. These disaccharides gradually accumulate in the lysosomes and cause cells to malfunction, resulting in the signs and symptoms of beta-mannosidosis.

Associated Gene

  • MANBA

Inheritance

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have variants. The parents of an individual with an autosomal recessive condition each carry one copy of the altered gene, but they typically do not show signs and symptoms of the condition.

Other Names for This Condition

  • Beta-D-mannosidosis
  • Beta-mannosidase deficiency
  • Lysosomal beta A mannosidosis
  • Lysosomal beta-mannosidase deficiency

Frequently Asked Questions

Diagnosis usually begins with clinical evaluation and is confirmed through biochemical and genetic testing. A key diagnostic test is the measurement of beta-mannosidase enzyme activity in white blood cells or fibroblasts; low levels of this enzyme indicate the disorder. Genetic testing for variants in the MANBA gene can also confirm the diagnosis and identify the specific mutations. Newborn screening programs in some regions may detect elevated levels of mannose-containing oligosaccharides in the urine, which can prompt further investigation.
The impact on daily life varies significantly depending on the severity of the condition. Many individuals require assistance with daily activities due to intellectual disability and motor impairments. Long-term prognosis is generally guarded, with many patients experiencing a gradual decline in function over time. Complications such as recurrent respiratory infections, hearing loss, and peripheral neuropathy can further affect quality of life. Early intervention and comprehensive care can help maximize independence and manage symptoms, but the condition is lifelong and requires ongoing medical supervision.
Early signs in infants can be subtle and may include developmental delays, such as difficulty achieving motor milestones like sitting or walking. Infants may also exhibit hypotonia (low muscle tone), feeding difficulties, or frequent respiratory and ear infections. As the child grows, distinctive facial features, such as a broad nasal bridge or thick eyebrows, may become apparent. Behavioral issues, including hyperactivity or aggression, and speech delays are also common early indicators that should prompt a referral to a geneticist or neurologist.
There is currently no cure for beta-mannosidosis. Treatment is supportive and focuses on managing symptoms. This includes physical, occupational, and speech therapy to address motor and communication delays. Medications may be prescribed to manage seizures, behavioral problems, or respiratory infections. Enzyme replacement therapy is under investigation but is not yet a standard treatment. Regular monitoring by a multidisciplinary team, including neurologists, pulmonologists, and geneticists, is essential to manage the progressive nature of the disorder and address complications as they arise.
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.

kontakt@hittavard.se

Ⓒ 2024. Alla rättigheter förbehålls av juxt ab

Sök
Om ossVillkor och policyVanliga frågorKontakta oss