The disease definition according to the specific consensus conference.
age, sex, seasonality, etc
PATIENT RISK FACTORS
TISSUE SPECIFIC RISK FACTORS
anatomical (due its structure)
vascular (due to the local circulation)
physiopathological (due to tissue function and activity)
Osteoporosis in patients with cystic fibrosis
Osteoporosis has been recognized as a complication of cystic fibrosis (CF). Both paediatric and adult CF physicians must now consider the skeletal health of their patients. (1)
CF osteoporosis may be a consequence of the gene defect, with the following risk factors being contributary (1) (2) (3):
• Malabsorption of fat soluble vitamins (e.g. Vitamines D, K), calcium (4) (5) (6) and malnutrition (7) (3)
Calcium is the principal mineral within the skeleton. In CF patients, vitamin D malabsorption secondary to pancreatic insufficiency and biliary disease may have a
negative effect on calcium absorption and bone homeostasis. Recent data suggests that calcium absorption from the gut is reduced in CF patients, even when pancreatic enzyme supplements are used.
Malabsorption of nutrients in CF may be a result not only of pancreatic insufficiency and
steatorrhea, but also of primary abnormalities in intestinal mucosal transport processes. Pancreatic enzyme supplements, commonly used by CF patients, would be expected to improve deficiencies due to pancreatic insufficiency but not other defects in intestinal function.
• Delayed puberty and Hypogonadism (1) (8) (9) (10)
Hypogonadism is common in CF and is associated with low bone mass. Malnutrition, a
major cause of pubertal delay, may explain the high incidence of pubertal delay, hypogonadism and osteopenia in CF adolescents.
• Reduced Physical activity (1) (5) (11)
Physical activity, particularly weight bearing activity, is an important determinant of bone mass.
• Glucocorticoid therapy (12)
Glucocorticoid are frequently used to treat patients with pulmonary diseases, but continuous long term use of glucocorticoids may lead to significant bone loss and increase risk of fragility fractures.
• Cyclosporin therapy (1) (13) (7)
After transplantation, the use of lifelong immunosuppressants may exacerbate the risk for osteoporosis and osteonecrosis in patients with CF
• Chronic infection (5) (14) (1) (15) (16)
A CF specific determinant of bone loss may be disease severity. A possible negative effect of disease severity on BMD may be mediated by its effects on body weight, as
chronic pulmonary and pancreatic disease leads to greater degrees of malnutrition. Additionally, release of cytokines such as tumour necrosis factors-α, transforming growth
factor-β, interleukin-1 and interleukin-6, in response to chronic pulmonary sepsis, may also increase bone resorption because they are osteoclast activating factors
• Association with CFTR genotype (1) (17) (18) (19)
Cystic fibrosis is the most common and best-known genetic disease involving a defect in transepithelial Cl– transport. CFTR, the cystic fibrosis transmembrane conductance regulator functions as a cAMP- and ATP-regulated Cl– channel. It is not known whether the CF transmembrane regulator (CFTR) protein is expressed in normal bone. Probably It localizes to the acid-secreting ruffled border, which is formed by the exocytotic insertion of H+-ATPase–containing vesicles of late endosomal/lysosomal origin. It was suggested that CFTR, like ClC-7 is co-inserted with the H+-ATPase into this membrane and serves as a shunt for the acidification of the resorption lacuna. This acidification is crucial for the chemical dissolution of inorganic bone material, as well as for the activity of cosecreted lysosomal enzymes that degrade the organic bone matrix. The alterated functioning of the osteoclasts induce a reduced activity of the osteoblasts, and conseguently a reduced bone density.
• Diabetes (1)