INTRODUCTION
Bronchiectasis is a condition characterized by irreversible abnormal dilation and anatomic breakdown of the bronchial tree. Although the frequency pf bronchiectasis has been declining due to the improvement in nutrition and sanitation circumstances, increased rate of vaccination and early and frequent use of antibiotics, it still causes a serious health problem in developing countries (1,2). Pifferi et al. reported the frequency of bronchiectasis as 1/6000 in general pediatric population in their study in 2004 (3).
The most common cause of bronchiectasis in developed countries is Cystic Fibrosis (CF). Bronchiectatic patients with CF and noncystic fibrosis have many common features. Chronic and recurrent lung infections, chronic inflammation, inhaled corticosteroid use in inactivity and acute exacerbations, bronchial hyperreactivity and nutritional problems are the characteristic features of both groups of diseases (4).
Osteoporosis and osteopenia were reported to be more frequent in patients diagnosed with CF and noncystic fibrosis bronchiectasis compared to normal population and the frequency was reported to increase with increasing age (4-5).
Osteoporosis is a systemic bone disease characterized with decreased bone mineral density (BMD) and impairment of inner architecture. The amount of mineralization is normal in all forms of osteoporosis, while decreased bone volume in especially trabecular bone and decreased trabecular bone cycle is noticed. Osteoporosis is evaluated using BMD, dual-energy X-ray absorptiometry (DEXA), quantitative computed tomography (QCT) and quantitative ultrasonography (QUS). Osteoporosis is frequently encountered in chronic diseases, especially with long hospital stay, inadequate vitamin D intake and drug use. Vitamin K and D deficiency in cystic fibrosis is thought to be associated with osteoporosis (6).
Many mechanisms are responsible in the development of osteoporosis. Bone resorption secondary to the changes in RANK-RANKL-OPG system is in the forefront recently (7). OPG is a member of the receptor TNFR super family, and is also known as TNFRS11B. Another name of it is osteoclastogenesis inhibitory factor (OCIF). Original OPG molecule is a polypeptide composed of 401 amino acids, and the mature protein composed of 380 amino acids is formed by separation of the 21-amino acid propeptide part.
The association between osteoporosis and RANKL/OPG levels has been demonstrated in the literature in patients with CF in whom bronchiectasis is common. However, no study has been published evaluating the association between osteoporosis and RANKL/OPG levels in patients with noncystic fibrosis bronchiectasis. The aim of this study was to measure the RANKL and OPG levels in patients with noncystic fibrosis bronchiectasis and with osteoporosis. And to evaluate the applicability of using RANKL and OPG levels as markers in the early diagnosis of osteoporosis and its follow-up.