To clarify pseudo-obstruction treatment in myotonic dystrophy.

Myotonic dystrophy type 1 (DM1) is an autosomal dominant, multiorgan disease causing skeletal muscle weakness and myotonia, cardiac disease, and gastrointestinal (GI) dysmotility. Constipation, bloating, and pain can have many causes in DM1, sometimes resulting from neurogenic or myogenic dysmotility that leads to acute or chronic intestinal pseudo-obstruction (CIPO). DM1 patients with exacerbations of CIPO may present with an acute abdomen and ileus. Conservative management of CIPO exacerbations includes bowel rest and decompression, intravenous fluids, pro-kinetic agents, and antibiotics for possible small intestine bacterial overgrowth. CIPO is an underrecognized motility disorder that is frequently misdiagnosed as a mechanical small bowel obstruction (SBO) – a potential surgical emergency. Hyoscyamine, a non-selective, competitive muscarinic antagonist that inhibits GI parasympathetic activity was postulated to relax GI musculature and relieve CIPO in DM1 that results from overactive parasympathetic activity. Hyoscyamine has not been previously described in the management of pseudo-obstruction in DM1.

We present four cases of patients with DM1 and CIPO presenting with acute exacerbations. The first are identical twin brothers, one presenting with acute abdomen with ileus who underwent emergency exploratory laparotomy where colonic pseudo-obstruction was directly visualized. In subsequent admissions, both patients’ symptoms were refractory to conservative management but markedly improved when hyoscyamine was administered. In the latter two cases, ambulatory patients with CIPO exacerbations presented with acute abdomens with ileus, and hyoscyamine led to rapid resolution of symptoms in the Emergency Department, avoiding unnecessary laparotomies.

Contrary to conventional use of pro-kinetic treatment for CIPO exacerbations in DM1, hyoscyamine, an anti-cholinergic medication, can sometimes rapidly resolve severe symptoms and avoid unnecessary procedures in patients at high risk of GI or systemic complications. These four cases highlight the important potential use of hyoscyamine in acute exacerbations of CIPO.