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GI / Nutrition Overview

The gastrointestinal tract is an important and often overlooked site of mitochondrial disease symptoms.  Gastrointestinal abnormalities may be an early presenting sign of mitochondrial disease (Chitkara, 2003).  In general, patients with GI symptoms do not get referred for a metabolic or mitochondrial evaluation unless neurological symptoms are also present.  Mitochondrial disease should be part of the differential diagnosis for individuals with dysmotility, chronic diarrhea, constipation or chronic abdominal pain (Chitkara, 2003).

Muscle weakness or fatigue of the muscles of mastication can directly interfere with the physical intake of adequate calories.  Because of muscle fatigue, patients may avoid foods that require a lot of chewing, tending toward softer solids or fluids, or may have issues with swallowing. 

Beyond the mouth, the symptoms relate primarily to problems with sympathetic and parasympathetic (autonomic) control of peristalsis that can impact any level of the GI tract.  Described pathology includes visceral myopathy with atrophic fibrotic longitudinal smooth muscle and normal ganglionic cells in the intestinal wall.  In other cases, findings have shown fibrosis and vacuolization of autonomic ganglia in the mysenteric plexus and decreased nerve fibers innervating intestinal smooth muscle (Gillis, 2003).  Axelrod (2006) has proposed that an abnormal gastrointestinal-brain axis (which includes neuro-endocrine and autonomic components) results in disruption of gastrointestinal function. 

Dysmotility can result in gastroesophageal reflux, delayed gastric emptying or gastroparesis, pseudo-obstruction, and/or constipation.  Associated symptoms can include dysphagia, early satiety or anorexia, nausea and vomiting, bloating, all with or without abdominal pain.  Anorexia and/or poor calorie intake can result in failure to thrive.  On occasion, the underlying disease directly results in severe growth retardation.

In patients who have central nervous involvement (e.g., bulbar weakness), the abnormal neurologic state can itself be associated with many of these same symptoms including uncoordinated swallowing and reflux (causing gagging, choking and/or vomiting), as well as constipation.

When GI involvement is significant enough to cause failure to thrive and weight loss, other symptoms, already present, can become more intense leaving an impression that the disease is progressing; exercise intolerance and muscle pain may worsen, and headaches and migraine may become more severe and frequent.  Autonomic symptoms including dizziness often become more prominent.  The benefits of vitamin supplementation may be minimal or not realized in an undernourished (or underhydrated) patient.  Many of the symptoms can be reversed or improved with a resumption of consistent and adequate nutritional intake through direct enteral feedings or parenteral nutrition.

Diverticulitis may also be associated with disordered gut motility, and ischemic colitis with diarrhea has also been described (Gillis, 2003), although whether or not these are true associations with mitochondrial disease or coincidental findings is not clear.

In addition, liver disease is described in mitochondrial disease which can range in severity from non-specific liver dysfunction, to fatty liver, hepatic insufficiency, or full cirrhosis (Gillis, 2003).  Associated symptoms may include failure to thrive and/or coagulopathy.  Patients with mitochondrial disease may be at risk for adverse effects associated with the use of certain medications that impact the respiratory chain such as valproic acid (Chabrol, 1994) and medications prescribed for HIV infections (Gillis, 2003).

Pancreatic insufficiency is described in Pearson syndrome but may occur less commonly in other mitochondrial diseases.  Pancreatic involvement may present as failure to thrive, chronic diarrhea, and fat malabsorption. 

References

Axelrod FB, Chelimsky GG, Weese-Mayer DE.  Pediatric autonomic disorders.  Pediatrics 2006;118(1):309-321.

Bindoff L.  Mitochondrial gastroenterology.  In Mitochondrial Medicine.  DiMauro S, Hirano M, Schon EA, eds.  Informa Healthcare, Abingdon UK, 2006, 143-60.

Chabrol B, Mancini J, Chretien D, et al.  Cytochrome c oxidase defect, fatal hepatic failure, and valproate: A case report.  Eur J Pediatr 1994;153:133-5. 

Chitkara DK, Nurko S, Shoffner JM, Buie T, Flores A.  Abnormalities in gastrointestinal motility are associated with diseases of oxidative phosphorylation in children.  Am J Gastroenterol 2003; 98(4):871-7.

Gillis LA, Sokol RJ.  Gastrointestinal manifestations of mitochondrial disease.  Gastroenterol Clinics North Am 2003;32(3):789-817.

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