Interstitial lung disease is often accompanied by disorders of vitamin D metabolism and related to them disorders of bone mineralization. According to literature data, loss of bone mass is present in up to 80% of patients suffering from the above mentioned respiratory diseases, of which osteoporosis is approx. 44% of the cases (1). Interstitial lung diseases are quite heterogeneous collection of about 200 diseases of different etiology, and clinical course, divided arbitrarily several years ago in four main groups: a disease of known cause (e.g. side effects of drugs or diseases of the connective tissue), idiopathic interstitial pneumonia, granulomatous diseases, and other (e.g. pulmonary eosinophilia, lymphangioleiomyomatosis, etc.) (2). Sarcoidosis takes second place on the list of the most often occuring interstitial diseases of the respiratory system, after idiopathic pulmonary fibrosis and before allergic alveolitis (2).

Sarcoidosis occurs in all ages, with a peak incidence among young adults (20-40 years) (3). Women and black people are particularly exposed. In some highly industrialized countries (e.g. Sweden) can be observed the second peak incidence in women over 50 years of age. Children are rarely suffering from sarcoidosis, and it is rather benign (2, 3). Not becoming caseous granuloma that are composed of epitheloid cells, multinucleated giant cells, macrophages and lymphocytes are typical pathomorphological changes in sarcoidosis. Epithelioid cells emerging from activated macrophages and multinucleated giant cells occupy the central part of the granuloma, and the helper CD4 lymphocytes gather around them. Sarcoidosis is a systemic disease, and sarcoidal granulomas may appear in virtually every organ of the body, yet most frequently (in 90% of cases) can be found in pulmonary parenchyma (2, 4).

In sarcoidosis, as in the case of other interstitial lung diseases for example idiopathic pulmonary fibrosis and other chronic diseases, e.g. rheumatoid arthritis, there is an increased risk of bone mineralization disorders (4, 5). According to literature data, nearly 55% of patients with sarcoidosis without accompanying chronic diseases have reduced bone mineral density (osteopenia or osteoporosis). Furthermore, in nearly a quarter of patients with this disease with normal density of bone mass may occur low-energy fractures of the skeletal system (5).

Disorders of bone mineralization in patients with sarcoidosis result from the possible need for prolonged systemic glucocorticoid use in therapy and chronic systemic inflammatory response accompanying disease (4, 5). In addition, the condition of the bone system is affected by (fairly specific for sarcoidosis) pathomechanisms of calcium and vitamin D metabolism disorders primarily related with non-renal production of excessive amounts of active metabolites of vitamin D (calcitriol) by sarcoidal granulomas which results in hypercalcemia and hypercalciuria. Less often abnormal bone mineralization in sarcoidosis results from direct seizure of the bone system by sarcoidal granulation tissue because, according to the literature, direct damage to the bone affected by the disease occurs in about 1.5 to 13% of patients with sarcoidosis (7, 8).