The overall objective is to evaluate the long-term efficacy, safety and tolerability of repeated Lamazym i.v. treatment in patients 5-21 years of age with alpha-Mannosidosis

Inclusion Criteria:

• The subject must have participated in the phase 1 trial (EudraCT number: 2010-022084-36) and phase 2a trial (EudraCT number: 2010-022085-26)
• Subject or subjects legally authorized guardian(s) must provide signed, informed consent prior to performing any trial-related activities (trial-related activities are any procedures that would not have been performed during normal management of the subject)
• The subject and his/her guardian(s) must have the ability to comply with the protocol

Exclusion Criteria:

• The subject cannot walk without support
• Presence of known chromosomal abnormality and syndromes affecting psychomotor development, other than alpha-Mannosidosis
• History of bone marrow transplantation
• 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: Before the start of the treatment the investigators will decide whether or not there is a need for contraception. This assessment will be done through interviews with the patient and parents. The evaluation will be done continuously during the study
• Psychosis within the last 3 months
• Planned major surgery that, in the opinion of the investigator, would preclude participation in the trial
• Participation in other interventional trials testing IMP except for studies with Lamazym