Osteopenia in Gaucher disease develops early in life: response to imiglucerase enzyme therapy in children, adolescents and adults.

BACKGROUND: In Gaucher disease (GD), acid-β-glucosidase (GBA1) gene mutations result in defective glucocerebrosidase and variable combinations of hematological, visceral, and diverse bone disease. Osteopenia is highly prevalent, but its age of onset during the natural course of GD is not known. It is also unclear if the degree of improvement in osteopenia, secondary to imiglucerase enzyme therapy, differs by the age of the patient.
OBJECTIVE: We hypothesized that osteopenia develops early in life, during the natural course of type 1 Gaucher disease (GD1), and that its response to treatment is maximal during this period.
METHODS: We examined data from the International Collaborative Gaucher Group (ICGG) Gaucher Registry of patients treated with imiglucerase between the ages of 5 and 50 years. Lumbar spine bone mineral density (BMD) (determined by dual-energy X-ray absorptiometry (DXA) and expressed as Z-scores) at baseline and for up to 10 years on imiglucerase were analyzed in children (ages ≥ 5 to <12 years), adolescents (≥ 12 to <20 years), young adults (≥ 20 to < 30 years), and older adults (≥ 30 to < 50 years). BMD was correlated with other disease characteristics. Pre-treatment, descriptive statistics were applied to 5-year age categories. Non-linear mixed effects regression models were used to analyze DXA Z-scores over time after treatment with imiglucerase.
RESULTS: Pre-treatment, low BMD was prevalent in all age groups, most strikingly in adolescents. DXA Z-scores were at or below -1 in 44% of children (n=43), 76% of adolescents (n=41), 54% of young adults (n=56) and 52% of older adults (n=171). The most common GBA1 genotype was N370S heteroallelic. Baseline hematological and visceral manifestations in the 4 age groups were similar. In children with DXA Z-scores ≤-1 at baseline, imiglucerase therapy for 6 years resulted in improvement of mean DXA Z-scores from -1.38 (95% CI -1.73 to -1.03) to -0.73 (95% CI -1.25 to -0.21); in young adults DXA Z-scores improved from -1.95 (95% CI -2.26 to -1.64) to -0.67 (95% CI -1.09 to -0.26). BMD also improved in older adults, but the magnitude of the improvement was lower compared to younger patients.
CONCLUSIONS: Low bone density is common in GD1 with the highest prevalence rate in adolescence, a developmental period critical to attainment of peak bone mass. Imiglucerase results in amelioration of osteopenia in all age groups, with the greatest improvements in younger patients.