Bone mineral density in children, adolescents and adults with glycogen storage disease type Ia: A cross-sectional and longitudinal study

The occurrence of (symptoms related to) osteopenia is a known complication in glycogen storage disease type Ia (GSD Ia) patients. However, only limited information is available about bone mineral density (BMD). Using dual energy x-ray absorptiometry, we studied both cross-sectional and longitudinal lumbar spine areal BMD(BMDareal in g/cm(2)), areal BMD corrected for delayed bone maturation (BMDbone age in g/cm(2)), and volumetric BMD (BMDvol in g/cm(3)). Prepubertal GSD Ia patients (n=8) had normal BMD (median z-scores BMDareal -0.6, BMDbone (age) -0.5 and BMDvol -0.5), whereas adolescent patients (n=12) and adult patients (n=9) had significantly reduced BMD (BMDareal -2.3, BMDbone age -1.6, BMDvol -2.0, and BMDareal -1.9, BMDvol -1.5, respectively). Our longitudinal study, showing a stable BMDareal but a trend to a decrease in BMDvol in prepubertal patients during follow-up, did not clarify whether the difference in BMD between prepubertal and adolescent/adult patients reflects a diminished accretion of BMD during childhood or reflects historical differences in treatment. In adolescent and adult GSD Ia patients, BMDareal and BMDvol were reduced but stable during follow-up. Especially patients with delayed bone maturation were at risk for reduced BMD. No correlation between parameters of metabolic control and BMD could be detected. Daily calcium intake was within recommended allowances ranges. Abnormal biochemical results included hypomagnesaemia (29%), hypercalciuria (34%) and reduced tubular resorption of phosphate (21%). Although the underlying pathophysiology of reduced BMD in GSD Ia remains unsolved, metabolic control should be optimized to correct as much as possible metabolic and endocrine abnormalities that may influence both bone matrix formation and bone mineral accretion.