Food intolerance/malabsorption may occur in rare diseases.

Sugars including lactose and fructose, or proteins (gluten), or biogenic amines (histamine), and combinations thereof may cause food intolerance/malabsorption. However, in usually asymptomatic patients with rare diseases, who present with functional, non-specific, non-allergic gastrointestinal (GI) complaints the etiologic factors of food intolerance/malabsorption need to be evaluated. We summarize patients with rare diseases, such as primary epiploic appendagitis, beta-thalassemias minor, Gullo syndrome and anomaly of the inferior vena cava, who presented functional, non-specific, non-allergic GI complaints. As conclusion, these GI symptoms in patients with otherwise asymptomatic, rare diseases were due to fructose malabsorption, histamine-, lactose intolerance and () infection. A registered and experienced dietician was employed to design an individually-tailored diet which ensured effective treatments and infection was accordingly eradicated.