The most common manifestations are diarrhoea, weight loss and general weakening, abdominal bloating and abdominal pain, vomiting, and, in children, retardation of growth. Other symptoms can manifest themselves outside the intestine, such as anaemia, osteoporosis, amenorrhea and vitamin or mineral deficiencies. Some symptoms come from pathologies that are associated with the condition. The coeliac condition does not always present itself in the same way, however; it has various clinical forms, and these must be taken into account during the diagnostic phase. The various clinical manifestations of the coeliac condition can be divided into typical cases with marked gastrointestinal symptoms (these cases are in the minority today) and the more frequent atypical cases, which are characterised by vague symptoms such as colitis (the so-called “irritable bowel”) or an iron deficiency that is resistant to oral therapy. There are also the silent forms, which are occasionally diagnosed in subjects at risk (family members of coeliacs, for example, or diabetics who are subjected to serological screening) despite the absence of obvious symptoms. In such cases, the apparent lack of symptoms is misleading; after treatment begins, a marked improvement in overall well-being is noted. Finally, the condition is suspected in some patients because they have a non-intestinal complaint that may be associated with the coeliac condition, such as dermatitis herpetiformis, aphthous stomatitis, diabetes, osteoporosis, fertility disorder, thyroiditis, allergies, food intolerance, or a neurological pathology. In individual – fortunately very rare – cases, the coeliac condition manifests itself from the onset with severe complications such as ulcerative jejunoileitis or intestinal lymphoma.