A Placebo-Controlled Phase 3 Trial of Repeated Lamazym Treatment of Subjects With Alpha-Mannosidosis

Inclusion Criteria: * Subject or subjects legally authorized guardian(s) must provide signed, informed consent prior to performing any trial-related activities * The subject and his/her guardian(s) must have the ability to comply with the protocol * The subject must have a confirmed diagnosis of alpha-Mannosidosis as defined by alpha-Mannosidase activity \< 10% of normal activity (historical data) * The subject must have an age at the time of screening ≥ 5 years and ≤ 35 years * The subject must have the ability to physically and mentally cooperate in the tests * The subject must have an ECHO without abnormalities that, in the opinion of the Investigator, would preclude participation in the trial Exclusion Criteria: * The subjects diagnosis cannot be confirmed by alpha-Mannosidase activity \< 10% of normal activity * The subject cannot walk without support * Presence of known chromosomal abnormality and syndromes affecting psychomotor development, other than alpha-Mannosidosis * History of BMT * Presence of known clinically significant cardiovascular, hepatic, pulmonary, or renal disease or other medical conditions that, in the opinion of the Investigator, would preclude participation in the trial * Any other medical condition or serious intercurrent illness, or extenuating circumstance that, in the opinion of the Investigator, would preclude participation in the trial * Pregnancy: Pregnant woman is excluded. Before start of the treatment the investigators will for women of childbearing potential perform a pregnancy test and decide whether or not there is a need for contraception * Psychosis; any psychotic disease, also in remission, is an exclusion criteria * Planned major surgery that, in the opinion of the Investigator, would preclude participation in the trial * Participation in other interventional trials testing IMP (including Lamazym) within the last 3 months * Adult patients who, in the opinion of the Investigator, would be unable to give consent, and who does not have any legal protection or guardianship * Total IgE \>800 IU/ml * Known allergy to the IMP or any excipients (Sodium-Phosphate, Glycine, Mannitol)