Abstract Coeliac disease (CD, sometimes called gluten-sensitive enteropathy or nontropical sprue) is an inflammatory disorder of the small intestine of autoimmune origin. It occurs in genetically predisposed people and is induced by a gluten protein, which is a component of wheat. The prevalence of histologically confirmed CD is estimated in screening studies of adults in the United States and Europe to be between 0.2% and 1.0%. The results of previous studies have indicated that the prevalence of CD is increased in patients with other autoimmune disorders such as: autoimmune thyroid diseases, type 1 diabetes mellitus, and Addison’s disease. A coincidence of the above diseases constitutes autoimmune polyglandular syndrome (APS). The high prevalence of CD in APS is probably due to the common genetic predisposition to the coexistent autoimmune diseases. The majority of adult patients have the atypical or silent type of the disease. This is the main reason why CD so often goes undiagnosed or the diagnosis is delayed. CD, if undiagnosed and untreated, is associated with many medical disorders including haematological (anaemia), metabolical (osteopenia/osteoporosis), obstetric-gynaecological (infertility, spontaneous abortions, late puberty, early menopause), neurological (migraine, ataxia, epilepsy) as well as with an increased risk of malignancy, especially: enteropathy-associated T-cell lymphoma, small intestine adenocarcinoma, and oesophageal and oropharyngeal carcinomas. Early introduction of a gluten-free diet and lifelong adherence to this treatment decreases the risk of these complications.