Small intestinal bacterial overgrowth in systemic sclerosis

Systemic sclerosis is a multi-organ autoimmune disease characterized by vasculopathy and fibrosis, and it is arguably the most devastating of the rheumatological diseases. The gastrointestinal tract is the most commonly involved internal organ in systemic sclerosis. Gastrointestinal tract involvement is reported in up to 90% of SSc patients, is the leading cause of morbidity, and is the third most common cause of mortality in this disease. Among all gastrointestinal tract manifestations, small intestinal bacterial overgrowth is one manifestation that may be ameliorated and even eradicated with appropriate treatment, if recognized early. Small intestinal bacterial overgrowth occurs with a prevalence of approximately 39% in systemic sclerosis and presents with a range of non-specific gastrointestinal tract symptoms, including diarrhea, flatulence, abdominal pain, bloating, and early satiety. These manifestations occur due to an alteration and overgrowth of small intestinal bacteria occurring in the setting of gastrointestinal tract dysmotility and slow transit time. The clinical diagnosis of small intestinal bacterial overgrowth is commonly based on the presence of characteristic clinical symptoms together with a positive hydrogen breath test and response to a therapeutic trial of oral antibiotics used sequentially. Almost two-thirds of systemic sclerosis patients with small intestinal bacterial overgrowth have an improvement in their gastrointestinal tract symptoms with rotating antibiotics. Untreated small intestinal bacterial overgrowth can lead to malnutrition, and thus an important aspect of treatment is the identification and treatment of any associated vitamin and mineral deficiencies. This article focuses on small intestinal bacterial overgrowth, an important and understudied area in systemic sclerosis that remains a diagnostic and therapeutic challenge for both patients and clinicians alike.