Mastocytosis is a rare and heterogeneous group of diseases whose common element is the presence of dense mast-cell infiltrates in various tissues. The gastrointestinal (GI) tract is frequently affected with vague and subtle manifestations, making the diagnosis of GI mastocytosis rather formidable and challenging. The diagnosis of the disease requires a high level of clinical suspicion and an index of familiarity. To our knowledge, this is the first case of indolent systemic mastocytosis with colonic ulcerations. Because of the unusual presentation of mastocytosis, it was initially misdiagnosed as Crohn's disease; the diagnosis of mastocytosis was established after further evaluation of the patient's history and further investigation. Systemic mastocytosis should therefore be considered in the differential diagnosis in patients presenting with abdominal manifestations that cannot be otherwise explained or attributed to common GI pathologies and in cases where the patient's trajectory does not follow the expected course. More research is needed into the epidemiology and the non-classical presentation of systemic mastocytosis in order to increase awareness of the disease in the medical community.