Low bone mass in Pompe disease: muscular strength as a predictor of bone mineral density.
Pompe disease is an inherited metabolic myopathy caused by deficiency of acid alpha-glucosidase. The introduction of enzyme replacement therapy as treatment for the disease may change prospects for patients and may require that more attention be paid to co-morbidities such as osteoporosis.


METHODS
Bone mineral status was assessed in children and adults with Pompe disease and compared with reference values by means of dual energy X-ray absorptiometry (DXA) technology (GE Lunar DPX, GE Health Care). Bone mineral density (BMD) of the total body and the lumbar spine (L2-L4) was measured in adults and children; BMD of the femoral neck was measured in adults only. Exclusion criteria were: age<4 years, severe contractures, and inability to transfer the patient.


RESULTS
46 patients were enrolled in the study; 36 adults and 10 children. The BMD was significantly lower in Pompe patients than in healthy individuals. Sixty-seven percent of patients had a BMD Z-score below -1, 26% were classified as osteoporosis/low bone mass for chronological age (T-score<-2.5 in adults or Z-score<-2 in children), 66% had a BMD Z-score below -1 of the femoral neck, and 34% had a BMD Z-score below -1 for the lumbar spine. Osteoporosis/low bone mass for chronological age was more frequent in patients who were wheelchair-bound, but was also observed in ambulant patients. We found a significant correlation between proximal muscle strength and total body BMD. Of the 10 children, 8 (all four patients with the classic infantile form) had a low BMD.


CONCLUSIONS
Low BMD is a frequent finding in patients with Pompe disease and may be causally related to decreased proximal muscle strength. BMD should be monitored at regular intervals. Children deserve specific attention.
van den Berg
Linda E M
LE
Department of Pediatrics, Division of Metabolic Diseases and Genetics, Center for Lysosomal and Metabolic Diseases, Erasmus MC University Medical Center, Rotterdam, The Netherlands. l.vandenberg@erasmusmc.nl
Zandbergen
Adrienne A
AA
van Capelle
Carine I
CI
de Vries
Juna M
JM
Hop
Wim C
WC
van den Hout
Johanna M
JM
Reuser
Arnold J J
AJ
Zillikens
M Carola
MC
van der Ploeg
Ans T
AT
D015502:Absorptiometry, Photon; D000293:Adolescent; D000328:Adult; D015519:Bone Density; D002648:Child; D002675:Child, Preschool; D005260:Female; D006009:Glycogen Storage Disease Type II / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D000520:alpha-Glucosidases / Q000172:deficiency
D000520:alpha-Glucosidases