P345 Dear doctor, could your patient’s unexplained gastrointestinal symptoms be caused by mast cell activation syndrome?

IntroductionMast Cell Activation Syndrome (MCAS) is a condition in which mast cells are inappropriately activated leading to inflammatory and allergic-type symptoms to everyday triggers such as food, chemicals, stress and more. Destabilisation of the mast cell has a direct impact on the gastrointestinal (GI) tract and patients with the symptoms of MCAS are often referred to a gastroenterologist for investigation.MethodsTo assess how MCAS impacts the GI system, the charity Mast Cell Action undertook a UK-wide online survey of adults and children (via their carers) with a confirmed or suspected diagnosis of MCAS. The survey evaluated symptoms most frequently experienced, tests and investigations commonly undertaken, and medical management strategies.ResultsThe survey was completed by 112 adults and on behalf of 30 children. A diagnosis of MCAS was confirmed in 68/112 (61%) of adults and 17/30 (57%) of children. The three most common GI symptoms were bloating (n=100 [89%]), pain (n=96 [86%]) and diarrhoea (n=90 [80%]) in adults, and pain (n=26 [87%]), GERD (n=24 [80%]) and constipation (n=22 [73%]) in children. Adults most frequently underwent investigation for coeliac disease (n=73 [65%]) and IBS (n=68 [61%]) whereas children underwent investigation for coeliac disease (n=16 [53%]), GERD (n=10 [33%]) and H. Pylori (n=8 [27%]). The surveyed patients had undergone a wide range of tests and investigations, with 72 adults (64%) and 14 children (47%) undergoing endoscopy and 59 adults (53%) and 8 children (27%) undergoing colonoscopy. In addition to MCAS, the most common diagnoses were IBS (n=48 [43%] and n=4 [13%], respectively), GERD (n=23 [21%] and n=7 [23%]) and coeliac disease (n=10 [9%] and n=2 [7%], respectively). Medical management strategies most frequently involve sodium cromoglicate, ranitidine, and PPIs. Diet modification was reported by 76 adults and 17 children; 32 adults and 13 children currently have a gastroenterologist leading their care.ConclusionsThis patient-reported survey indicates that MCAS patients experiencing GI symptoms are frequently investigated for a range of conditions. MCAS is notoriously difficult to diagnose, requiring a combination of multisystem symptoms, biological mediator test results and response to treatment.1 Although most recognised for its acute allergic symptoms (particularly anaphylaxis), the chronic symptoms of MCAS can be severely debilitating and significantly impact patient lives. GI symptoms are one of the most