title: Generalized metabolic bone disease in Neurofibromatosis type I.
abstract: Skeletal abnormalities are a recognized component of Neurofibromatosis type I (NF1) but a generalized metabolic bone defect in NF1 has not been fully characterized thus far. The purpose of this study was to characterize at the densitometric, biochemical and pathological level the bone involvement in NF1 patients. Using dual energy X-ray absorptiometry (DXA) we analyzed bone status in 73 unselected NF1 subjects, 26 males and 47 females, mainly children and adolescents (mean age: 16.6 years). In a subgroup of subjects with low bone mass, we measured indices of calcium-phosphate metabolism, bone turnover, and bone density before and after vitamin D and calcium treatment. We found statistically significant and generalized reduction in bone mass with the mean lumbar bone mineral density (BMD) z-score being -1.38+/-1.05 (CI 95% -1.62 to -1.13), and whole body bone mineral content (BMC) z-score -0.61+/-1.19 (CI 95% -0.94 to -0.29), both significantly reduced compared to normal controls (p<.001). PTH was moderately elevated and after 4 months of supplemental therapy with calcium and vitamin D, it decreased to the normal range. However, BMD z-scores did not significantly improve after 2 years of follow-up. Histological analysis of bone samples from NF1 patients revealed substantial alteration of bone microarchitecture due mainly to reduced trabecular bone. Our observations are consistent with a generalized bone metabolic defect due to loss of the function of neurofibromin. Early identification of patients with osteoporosis may permit more timely and aggressive treatments to prevent the likely substantial morbidity associated with increased fracture risk later in life.
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, One Baylor Plaza, Room 635E, Houston, TX 77030, USA.
authors.forename: Nicola
authors.initials: N
authors.lastname: Brunetti-Pierri
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Doty
authors.forename: John
authors.initials: J
authors.lastname: Hicks
authors.forename: Kelly
authors.initials: K
authors.lastname: Phan
authors.forename: Roberto
authors.initials: R
authors.lastname: Mendoza-Londono
authors.forename: Maria
authors.initials: M
authors.lastname: Blazo
authors.forename: Alyssa
authors.initials: A
authors.lastname: Tran
authors.forename: Susan
authors.initials: S
authors.lastname: Carter
authors.forename: Richard Alan
authors.initials: RA
authors.lastname: Lewis
authors.forename: Sharon E
authors.initials: SE
authors.lastname: Plon
authors.forename: William A
authors.initials: WA
authors.lastname: Phillips
authors.forename: E
authors.initials: E
authors.lastname: O'Brian Smith
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Ellis
authors.forename: Brendan
authors.initials: B
authors.lastname: Lee
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D000328:Adult; D015519:Bone Density; D001851:Bone Diseases, Metabolic / Q000209:etiology* / Q000473:pathology; D002118:Calcium / Q000097:blood; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009456:Neurofibromatosis 1 / Q000150:complications* / Q000175:diagnosis*; D010281:Parathyroid Hormone / Q000097:blood
chemical_list: D010281:Parathyroid Hormone; D002118:Calcium