Background Long-term complications of cystic fibrosis include osteoporosis and fragility fractures, but few data are available about effective treatment strategies, especially in young patients. We investigated treatment of low bone mineral density in children, adolescents, and young adults with cystic fibrosis.Methods We did a multicentre trial in two phases. We enrolled patients aged 5-30 years with cystic fibrosis and low bone mineral density, from ten cystic fibrosis regional centres in Italy. The first phase was an open-label, 12-month observational study of the effect of adequate calcium intake plus calcifediol. The second phase was a 12-month, double-blind, randomised, placebo-controlled, parallel group study of the efficacy and safety of oral alendronate in patients whose bone mineral apparent density had not increased by 5% or more by the end of the observational phase. Patients were randomly assigned to either alendronate or placebo. Both patients and investigators were masked to treatment assignment. We used dual x-ray absorptiometry at baseline and every 6 months thereafter, corrected for body size, to assess lumbar spine bone mineral apparent density. We assessed bone turnover markers and other laboratory parameters every 3-6 months. The primary endpoint was mean increase of lumbar spine bone mineral apparent density, assessed in the intention-totreat population. This study is registered with ClinicalTrials.gov, number NCT01812551.Findings We screened 540 patients and enrolled 171 (mean age 13.8 years, SD 5.9, range 5-30). In the observational phase, treatment with calcium and calcifediol increased bone mineral apparent density by 5% or more in 43 patients (25%). 128 patients entered the randomised phase. Bone mineral apparent density increased by 16.3% in the alendronate group (n=65) versus 3.1% in the placebo group (n=63; p=0.0010). 19 of 57 young people (33.3%) receiving alendronate attained a normal-for-age bone mineral apparent density Z score. In the observational phase, five patients had moderate episodes of hypercalciuria, which resolved after short interruption of calcifediol treatment. During the randomised phase, one patient taking alendronate had mild fever versus none in the placebo group; treatment groups did not differ significantly for other adverse events.Interpretation Correct calcium intake plus calcifediol can improve bone mineral density in some young patients with cystic fibrosis. In those who do not respond to calcium and calcifediol alone, alendronate can safely and effectively increase bone mineral density.

We describe a premature newborn child with left renal agenesis, right low functional kidney, altered chemical-clinical parameters, neutropenia, recurrent pulmonary infections, long bone diaphysis broadening, growth and developmental delay. Postnatal cytogenetic analysis revealed a 46,XY,t(2;7)(p13;p12) de-novo karyotype. The chromosome breakpoints were defined by FISH using BAC probes and initially restricted to about 123,000bp in 2p13 and delimited to 84,600bp in 7p12. Bioinformatic analysis of these genomic regions showed two genes that are involved in the rearrangement: exocyst C6B (EXOC6B) for chromosome 2 breakpoint and tensin3 (TNS3) for chromosome 7 breakpoint. A EXOC6B-TNS3 fusion transcript together with a reciprocal TNS3-EXOC6B chimeric RNA have been detected by RT-PCR performed on skin fibroblasts RNA of the proband. These data localize the chromosome 2 breakpoint within the first intron of EXOC6B, while the translocation event on chromosome 7 occurred in intron 15 of TNS3. We hypothesize that the phenotype observed in the patient results from one or several mechanisms including: haploinsufficiency of EXOC6B and TNS3 genes; a dominant negative effect exerted by the chimeric transcripts; a disregulation in the expression of other genes adjacent the breakpoints. Although no clear evidences exist supporting a role of any of the above mentioned mechanisms in the pathogenesis of the complex phenotype, immunofluorescence analysis of tensin1 in the patient's fibroblasts suggests that the TNS3 gene haploinsufficiency results in a reduced expression of tensin1. These cells may be therefore a model for understanding the role and the organization of the tensin protein family.