[57-year-old female patient in early retirement with underweight and chronic-relapsing diarrhoea].

Underweight as a consequence of chronic diarrhoea may lead to fatigue, tiredness and impaired physical performance, especially when the underlying cause has not been evaluated. In spite of algorithms as a help in the differential diagnosis, an individual approach with critical consideration of diet history, laboratory data and imaging procedures is necessary. Additional difficulties may arise when the history of food intolerance is inconsistent and technical findings including endoscopy are inconclusive. We report on a 57-year-old female patient with underweight, chronic intermittent diarrhoea and cramp-like abdominal pain for more than 10 years following pelvic irradiation due to Hodgkin's disease of the ovary. A systematic diagnostic approach was not undertaken until very recently due to the deterioration of her clinical conditions pointing to jejunal malabsorption. In spite of the absence of a specific history of milk/milk product intolerance a lactose H (2)-breath test was performed showing lactase deficiency with lactose intolerance. The rapid improvement of all her symptoms after a lactose-poor diet had been started supported this diagnosis. Possible reasons for the long time period which had elapsed until the diagnosis was established and the discrepancy of the H (2)-breath test results with the absence of a clear-cut history for milk/milk product intolerance are discussed in terms of the importance of a structured history-taking with regard to nutrition and diet habits. In addition, potential explanations for radiation-induced functional damage in the absence of morphological abnormalities are provided. Based on the experience of this case and considerations regarding the consequences of radiation-induced jejunal damage, we recommend that a lactose-H (2) breath test be routinely included in the diagnostic work-up of patients with unclear chronic diarrhoea even if there is no defined history of milk/milk product intolerance.