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PubMed This is a summary of 48 peer-reviewed journal articles Updated
Metabolic medicine

Alpha-mannosidosis: A Patient Guide

At a Glance

Alpha-mannosidosis is a rare inherited disorder in which complex sugars build up in cells and affect multiple body systems. There is no cure, but enzyme replacement therapy can help physical and immune health, and stem cell transplant may benefit carefully selected patients.

Alpha-mannosidosis is an ultra-rare, inherited condition that affects the way the body’s cells recycle certain sugars. It belongs to a family of diseases known as lysosomal storage disorders, where a missing or malfunctioning enzyme—in this case, lysosomal alpha-mannosidase—leads to a gradual buildup of complex, mannose-rich sugars within the cells [1][2]. Because these sugars accumulate in tissues throughout the entire body, the condition can impact many different systems, including hearing, bone development, the immune system, and the brain [2][3]. While frequently diagnosed in childhood, alpha-mannosidosis also affects adolescents and adults.

The experience of alpha-mannosidosis is highly variable, existing as a broad spectrum of severity rather than a single, predictable path. Historically, doctors have categorized the condition into types based on how early symptoms appear and how quickly they progress, but modern research views these as a continuous scale where one form may overlap with another [4][5]. While some individuals may face significant challenges early in life, others may have a slower progression that unfolds over many decades, making individualized care and consistent monitoring essential [2][3].

The landscape of care for this condition has transformed with the arrival of disease-specific treatments. While there is no cure, and treatments generally cannot reverse established neurological damage, families today have options that address the underlying cause of the disease. Enzyme replacement therapy (ERT) can help clear sugar buildup in the body to improve or stabilize physical mobility and immune health, while hematopoietic stem cell transplant (HSCT) may be considered for highly selected patients to potentially protect and stabilize cognitive and neurological function [6][7]. The urgency, eligibility, and choice of treatment must be individualized through shared decision-making with metabolic and transplant specialists [8][9].

Living with alpha-mannosidosis requires a lifelong partnership with a multidisciplinary team of specialists who coordinate care across every affected system of the body. From monitoring hearing and vision to supporting mental health and daily functioning, this team-based approach ensures that treatment is tailored to the patient’s changing needs [10][11]. While the diagnosis brings significant challenges, the combination of advanced medical care, genetic counseling, and a dedicated care team provides a roadmap to navigate the journey ahead [10][12].

In this guide

6 chapters

01

The Beginning of Your Journey: Understanding Alpha-Mannosidosis

Learn how alpha-mannosidosis affects the body, how MAN2B1 variants are inherited, why disease progression varies, and what monitoring and care may involve.

02

Signs and the Path to a Clear Diagnosis

Learn how alpha-mannosidosis symptoms lead to diagnosis, including oligosaccharide screening, enzyme activity, MAN2B1 gene testing, and ruling out MPS I.

03

Understanding Severity and How the Condition Changes Over Time

Learn how alpha-mannosidosis severity changes over time, including types, enzyme activity, mobility, learning, behavioral symptoms, and ongoing monitoring.

04

Standard of Care: Enzyme Replacement Therapy (ERT)

Learn about velmanase alfa ERT for alpha-mannosidosis, including weekly IV dosing, physical benefits, neurological limits, infusion risks, and monitoring.

05

The Choice of Transplant: Protecting the Brain

Learn how HSCT may protect the brain in alpha-mannosidosis, including candidate selection, timing, benefits, serious risks, and how it compares with ERT.

06

Building Your Care Team and Long-Term Monitoring

Learn how alpha-mannosidosis care teams coordinate long-term monitoring, specialist visits, mental health support, registries, and transition to adult care.

Common questions in this guide

What is alpha-mannosidosis, and which parts of the body can it affect?
Alpha-mannosidosis is a very rare inherited condition in which cells cannot properly break down certain sugars, so they build up in tissues. It can affect hearing, bone development, the immune system, the brain, and other body systems.
How does alpha-mannosidosis vary from person to person?
Alpha-mannosidosis occurs across a broad range of severity. Symptoms may begin in childhood, adolescence, or adulthood, and the condition may progress quickly in some people or more slowly over many years in others.
What treatments are available for alpha-mannosidosis?
There is no cure, but enzyme replacement therapy can help clear sugar buildup and may improve or stabilize mobility and immune health. A stem cell transplant may be considered for carefully selected patients to potentially protect or stabilize cognitive and neurological function.
How do doctors choose between enzyme therapy and a stem cell transplant?
Metabolic and transplant specialists consider the person’s symptoms, testing, severity, eligibility, treatment goals, and potential risks. The choice and timing are individualized through shared decision-making with the patient or family and the care team.
Can treatment reverse existing brain or nerve problems caused by alpha-mannosidosis?
Current treatments generally cannot reverse neurological damage that has already occurred. Enzyme replacement therapy mainly addresses effects throughout the body, while a stem cell transplant may help protect or stabilize cognitive and neurological function in selected patients.
What ongoing care does someone with alpha-mannosidosis need?
Care usually involves a multidisciplinary team that monitors hearing, vision, bone health, immunity, neurological function, mental health, and daily activities. Genetic counseling and coordinated support can help patients and families plan care as needs change.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on the specific symptoms and testing, where does my family member currently fall on the spectrum of severity?
  2. 2.What are the immediate next steps for assembling a multidisciplinary team of specialists?
  3. 3.How do we decide whether enzyme replacement therapy or a stem cell transplant might be appropriate options for our specific situation?
  4. 4.What resources, such as genetic counseling and patient organizations, are available to help our family navigate this diagnosis?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (12)
  1. 1

    The Application of HPLC-FLD and NMR in the Monitoring of Therapy Efficacy in Alpha-Mannosidosis.

    Krchňák M, Kodríková R, Matulová M, et al.

    Frontiers in bioscience (Landmark edition) 2023; (28(2)):39 doi:10.31083/j.fbl2802039.

    PMID: 36866557
  2. 2

    Hearing impairment as an early sign of alpha-mannosidosis in children with a mild phenotype: Report of seven new cases.

    Lehalle D, Colombo R, O'Grady M, et al.

    American journal of medical genetics. Part A 2019; (179(9)):1756-1763 doi:10.1002/ajmg.a.61273.

    PMID: 31241255
  3. 3

    Long-term outcome of patients with alpha-mannosidosis - A single center study.

    Lipiński P, Różdżyńska-Świątkowska A, Iwanicka-Pronicka K, et al.

    Molecular genetics and metabolism reports 2022; (30()):100826 doi:10.1016/j.ymgmr.2021.100826.

    PMID: 35242565
  4. 4

    Enzyme replacement therapy with velmanase alfa (human recombinant alpha-mannosidase): Novel global treatment response model and outcomes in patients with alpha-mannosidosis.

    Harmatz P, Cattaneo F, Ardigò D, et al.

    Molecular genetics and metabolism 2018; (124(2)):152-160 doi:10.1016/j.ymgme.2018.04.003.

    PMID: 29716835
  5. 5

    Ultra-orphan lysosomal storage diseases: A cross-sectional quantitative analysis of the natural history of alpha-mannosidosis.

    Zielonka M, Garbade SF, Kölker S, et al.

    Journal of inherited metabolic disease 2019; (42(5)):975-983 doi:10.1002/jimd.12138.

    PMID: 31222755
  6. 6

    Efficacy and safety of Velmanase alfa in the treatment of patients with alpha-mannosidosis: results from the core and extension phase analysis of a phase III multicentre, double-blind, randomised, placebo-controlled trial.

    Borgwardt L, Guffon N, Amraoui Y, et al.

    Journal of inherited metabolic disease 2018; (41(6)):1215-1223 doi:10.1007/s10545-018-0185-0.

    PMID: 29846843
  7. 7

    The Role of Hematopoietic Cell Transplant in the Glycoprotein Diseases.

    Naumchik BM, Gupta A, Flanagan-Steet H, et al.

    Cells 2020; (9(6)) doi:10.3390/cells9061411.

    PMID: 32517081
  8. 8

    Extended long-term efficacy and safety of velmanase alfa treatment up to 12 years in patients with alpha-mannosidosis.

    Guffon N, Borgwardt L, Tylki-Szymańska A, et al.

    Journal of inherited metabolic disease 2025; (48(1)):e12799 doi:10.1002/jimd.12799.

    PMID: 39381850
  9. 9

    Outcome of Haemopoietic Stem Cell Transplantation in 21 Patients With Alpha-Mannosidosis.

    Šáhó R, Formánková R, Eisengart JB, et al.

    Journal of inherited metabolic disease 2025; (48(4)):e70047 doi:10.1002/jimd.70047.

    PMID: 40551549
  10. 10

    Monitoring and integrated care coordination of patients with alpha-mannosidosis: A global Delphi consensus study.

    Guffon N, Burton BK, Ficicioglu C, et al.

    Molecular genetics and metabolism 2024; (142(4)):108519 doi:10.1016/j.ymgme.2024.108519.

    PMID: 39024860
  11. 11

    Long-term outcome of a cohort of Italian patients affected with alpha-Mannosidosis.

    Bertolini A, Rigoldi M, Cianflone A, et al.

    Clinical dysmorphology 2024; (33(1)):1-8 doi:10.1097/MCD.0000000000000474.

    PMID: 37791705
  12. 12

    Recognition of alpha-mannosidosis in paediatric and adult patients: Presentation of a diagnostic algorithm from an international working group.

    Guffon N, Tylki-Szymanska A, Borgwardt L, et al.

    Molecular genetics and metabolism 2019; (126(4)):470-474 doi:10.1016/j.ymgme.2019.01.024.

    PMID: 30792122

This page provides educational information about alpha-mannosidosis and does not constitute medical advice. A metabolic or transplant specialist can help your family interpret testing and decide whether enzyme therapy or stem cell transplant fits your situation.

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