Recommandations pour la prise en charge de la déminéralisation osseuse dans la mucoviscidose

Treatment of cystic fibrosis related bone disease

The advent of highly effective CFTR modulator therapies has slowed the progression of pulmonary complications in people with cystic fibrosis. There is increased interest in cystic fibrosis bone disease (CFBD) due to the increasing longevity of people with cystic fibrosis. CFBD is a complex and multifactorial disease. CFBD is a result of hypomineralized bone leading to poor strength, structure and quality leading to susceptibility to fractures. The development of CFBD spans different age groups. The management must be tailored to each group with nuance and based on available guidelines while balancing therapeutic benefits to risks of long-term use of bone-active medication. For now, the mainstay of treatment includes bisphosphonates. However, the long-term effects of bisphosphonate treatment in people with CF are not fully understood. We describe newer agents available for osteoporosis treatment. Still, the lack of data behooves trials of monoclonal antibodies treatments such as Denosumab and Romozosumab and anabolic bone therapy such as teriparatide and Abaloparatide. In this review, we also summarize screening and non-pharmacologic treatment of CFBD and describe the various options available for the pharmacotherapy of CFBD. We address the prospect of CFTR modulators on bone health while awaiting long-term trials to describe the effects of these medications on bone health.

[Insights into cystic fibrosis-related bone disease]

With the increasing life expectancy of patients with cystic fibrosis (CF), prevalence of late complications such as CF-related bone disease (CFBD) has increased. It was initially described in 24% of the adult population with CF and has also been reported in the pediatric population. CFBD is multifactorial and progresses in different steps. Both decreased bone formation and increased bone resorption (in different amounts) are observed. CFBD is likely primitive (directly related to the CFTR defect itself), but is also worsened by acquired secondary factors such as lung infections, chronic inflammation, denutrition, vitamin deficiency, and decreased physical activity. CFBD may be clinically apparent (i.e., mainly vertebral and costal fractures), or clinically asymptomatic (therefore corresponding to abnormalities in bone density and architecture). CFBD management mainly aims to prevent the occurrence of fractures. Prevention and regular monitoring of bone disease as early as 8 years of age is of the utmost importance, as is the control of possible secondary deleterious CFBD factors. New radiological tools, such as high-resolution peripheral quantitative computed tomography, allow an accurate evaluation of cortical and trabecular bone micro-architecture in addition to compartmental density; as such, they will likely improve the assessment of the bone fracture threat in CF patients in the near future.

Comparative bone status assessment by dual energy X-ray absorptiometry, peripheral quantitative computed tomography and quantitative ultrasound in adolescents and young adults with cystic fibrosis

PURPOSE

Quantitative ultrasound bone sonometry (QUS) might be a promising screening method for cystic fibrosis (CF)-related bone disease, given its absence of radiation exposure, portability of the equipment and low cost.The value of axial transmission forearm QUS in detecting osteopenia in CF was therefore studied.

METHODS

We investigated the application of QUS in the evaluation of bone status in a group of 64 adolescents (>12 years) and young adults (<40 years) with CF in a comparison with a dual X-ray absorptiometry (DXA) of the whole body and peripheral quantitative computed tomography (pQCT) of the radius at 4% and 66% sites.

RESULTS

Mean (SD) Z-scores of speed of sound (SOS), whole body bone mineral content (BMC), radial trabecular bone mineral density (BMD), and radial cortical BMD were respectively -0.31 (0.78), -0.09 (1.28), 0.10 (1.16) and -0.62 (2.88). The pQCT determined bone geometry values (cortical bone area and cortical thickness) were more depressed than the BMD data. QUS had a sensitivity and specificity of respectively 0% and 96% for diagnosing osteopenia (based on a whole body BMC Z-score<-2).

CONCLUSIONS

QUS cannot replace DXA, but can screen out patients with normal bone mass. Further and larger studies are needed to examine if QUS may reflect other aspects than bone mass, or if it is possible to improve its sensitivity by supplementing the SOS results with clinical risk factors.

Bone mineral and body composition alterations in paediatric cystic fibrosis patients

BACKGROUND

With the increased life span of cystic fibrosis (CF) patients, CF-related bone diseases could have an increased prevalence and morbidity in this group. In children, previous retrospective and prospective studies have yielded conflicting results on bone mineralization.

OBJECTIVE

To monitor body composition and bone mineral status of children with CF.

MATERIALS AND METHODS

We reviewed the dual-energy X-ray absorptiometry (DXA) data of 161 children with CF (age 10 +/- 4.8 years). Total body bone mineral content (BMCt), total lean tissue mass (LTMt) and total fat mass (FMt) were measured and compared to expected data calculated from ideal weight for height (Wi; e.g. BMCti, LTMti, FMti). The bt (BMCt/BMCti), lt (LTMt/LTMti) and ft (FMt/FMti) ratios were used as quantitative variables.

RESULTS

Low bt ratio was found at all ages (mean bt ratio 0.94 +/- 0.10; P < 0.001), even in children <6 years of age. However, the children's BMCt was satisfactorily adapted to their weight. lt and ft ratios were not constant across age groups. Children <10 years had 8% reduction of their lt ratio, maintaining normal levels thereafter. The opposite trend was found for ft ratio. Poor clinical, nutritional status and vitamin A levels were correlated with bt and lt ratios.

CONCLUSION

Our results indicate that children with CF could have early alterations in their bone status and that lt and ft ratios did not have constant values across ages. Interpreting DXA data using this approach is suitable in children with CF.

Update on cystic fibrosis-related bone disease: a special focus on children

A high prevalence of low bone mineralization is documented in adult patients with cystic fibrosis (CF). Osteopenia is present in up to 85% of adult patients and osteoporosis in 10% to 34%. In children, study results are discordant probably because of comparisons to different control populations and corrections for bone size in growing children. Malnutrition, inflammation, vitamin D and vitamin K deficiency, altered sex hormone production, glucocorticoid therapy, and physical inactivity are well known risk factors for poor bone health. Puberty is a critical period for bone mineralization and requires a careful follow-up to achieve optimal bone peak mass. Strategies for optimizing bone health, such as monitoring bone mineral density (BMD) and providing preventive care are necessary from childhood through adolescence to minimize CF-related bone disease in adult CF patients.