Natural history of alpha mannosidosis a longitudinal study

Abstract

Background: Alpha-Mannosidosis is a rare lysosomal storage disorder, caused by the deficiency of the enzyme alpha-Mannosidase. Clinically it is characterized by hearing impairment, skeletal and neurological abnormalities and mental retardation. In order to characterize the clinical features and disease progression of patients affected by alpha-Mannosidosis, a survey study was conducted. 43 patients from 4 European countries participated in this longitudinal study. Age range of the participants was 3 to 42 years. For each patient a medical history, complete physical and neurological examination, joint range of motion and assessment of physical endurance and of lung function were completed. In addition, serum and urinary oligosaccharide levels were analysed.

Methods: In this multicenter longitudinal study clinical data of 43 alpha-Mannosidosis patients were collected. In addition to objective clinical measurements biochemical assays were performed.

Results: Data analysis revealed a wide spectrum of clinical presentation regarding the severity and disease progression. Most clinical abnormalities were observed in the musculoskeletal and neurological system. All patients showed mental retardation and hearing loss from early childhood. An impairment in physical endurance was revealed by the 6-minute walk and 3-minute stair stair climb tests. There was only slight progression of a few clinical findings: Psychiatric troubles in both groups essentially, and respiratory dysfunction under 18 years. The serum and urinary oligosaccharide levels were increased in all affected individuals and correlated well with the 6-minute walk and 3-minute stair climb test results.

Conclusions: This study confirms that alpha-Mannosidosis is a very heterogeneous disorder regarding both, disease severity and progression. As it has been shown that Mannosidosis patients are able to perform lung function tests and the 6MWT and stair-climb test, these clinical parameters apparently can be used as clinical endpoints for clinical trials. Oligosaccharide levels appeared correlated with functional testing and may serve as biomarkers of disease severity, progression and response to treatment.

Trial registration: ClinicalTrials.gov Identifier = NCT00498420 and EuropeanCommission FP VI contract LHSM-CT-2006-018692.

Figure 1

Height of males with Alpha-Mannosidosis. Outer lines indicate - 2 SD and + 2 SD.

Figure 2

Height of females with alpha-mannosidosis. Outer lines indicate - 2 SD and + 2 SD.

Figure 3

Change of height of children and adults over time.

Figure 4

Hearing testing - bone conduction (dB HL). Mean ± SE (= 1 Standard deviation).

Figure 5

Hearing testing - air conduction: conventional frequency range (dB HL) mean ± SE (= 1 Standard deviation).

Figure 6

Hearing testing air conduction: high frequency range (dB HL) Mean ± SE (= 1 Standard deviation).

Figure 7

6-minute walk test: percentage of normal ± SE.

Figure 8

Lung function: range of FVC, expressed as percentage of expected depending on age, size and sex.

Figure 9

Lung function: percentage of predicted forced expiratory volume during first second.

Figure 10

6 minutes walk test (% of predicted) versus oligosaccharide level in urine by age group. Correlation Factor = 0,61602, P-Value = 0,0014).

Figure 11

Minutes stair climb test versus oligosaccharide level in urine by age group. Correlation Factor = 0,56805, P-Value = 0,0072).