Coeliac disease (CD) is a gluten intolerance caused by a combination of genetic and environmental factors such as nutrition and infections. Monozygotic twins appear to have a concordance for CD up to 71%. This paper reports a third case of late onset of CD in monozygotic twin girls. The twins were defined as monozygotic based upon paired clinical and laboratory examinations. Clinical examinations included genotypic, phenotypic and dermatoglyphic analysis, while laboratory examinations included HLA typing and blood groups. Following European Society of Pediatric Gastroenterology and Nutrition criteria, CD was diagnosed in both girls, though 4 years and 8/12 months apart. The twins achieved clinical, laboratory and histological remissions within 1 year, after the institution of a gluten-free diet. Genetic markers are undoubtedly the main precondition for CD development. Environmental factors, however, may play a more significant role in triggering the onset of disease.