Relationship between morphological findings and function of the small intestine in familial amyloidosis with polyneuropathy

Amyloid and the GI tract

Amyloidosis is characterized by the extracellular deposition of an abnormal fibrillar protein, which disrupts tissue structure and function. Amyloid may be localized to a single organ, such as the GI tract, or be systemic where the amyloid type is defined by the respective fibril precursor protein. Among patients with systemic amyloidosis, histological involvement of the gastrointestinal (GI) tract is very common but often subclinical. The presence and pattern of GI symptoms varies substantially, not only between the different amyloid types but also within them. GI presentations are frequently nonspecific and include macroglossia, dyspepsia, hemorrhage, a change in bowel habit and malabsorption. Endoscopic and radiological features of amyloidosis are also nonspecific, with the small intestine most commonly affected. In the absence of specific treatments for GI amyloidosis, therapy is aimed at reducing or eliminating the supply of the respective fibril precursor protein. Supportive measures such as nutritional support and antidiarrheal agents should be instigated while awaiting the clinical improvement associated with a successful reduction in the abundance of the fibril precursor protein. GI tract surgery should be performed only if the benefits clearly outweigh the risks, as there is a risk of decompensation of organs affected by amyloid.

Gastrointestinal manifestations of amyloidosis

Amyloidosis is characterized by extracellular deposition of abnormal protein. There are six types: primary, secondary, hemodialysis-related, hereditary, senile, and localized. Primary (AL) amyloidosis is associated with monoclonal light chains in serum and/or urine with 15% of patients having multiple myeloma. Secondary (AA) amyloidosis is associated with inflammatory, infectious, and neoplastic diseases. The presentation is protean, including macroglossia, a dilated and atonic esophagus, gastric polyps or enlarged folds, and luminal narrowing or ulceration of the colon. Amyloid deposition in the gastrointestinal (GI) tract is greatest in the small intestine. The symptoms include diarrhea, steatorrhea, or constipation. Pseudo-obstruction carries a particularly grave prognosis, often not responding to pro-motility agents. Hepatic involvement is common, but the clinical manifestations are usually mild with hepatomegaly and an elevated alkaline phosphatase level. Biopsies to diagnose amyloidosis can be taken from the fat, kidney, intestine, or bone marrow. The safety of liver biopsies is controversial. With Congo Red stain, amyloid appears red in normal light and apple-green in polarized light. Treatment for AL amyloidosis is chemotherapy and stem cell transplantation; treatment for AA amyloidosis is control of the underlying disease. Amyloidosis should be considered in patients with proteinuria, cardiomyopathy, hepatomegaly (with mildly abnormal liver tests), peripheral and autonomic neuropathy, weight loss, and GI symptoms.

Endoscopic and pathological manifestations of the gastrointestinal tract in familial amyloidotic polyneuropathy type I (Met30)

OBJECTIVES

To evaluate the characteristic changes in the gastrointestinal tract in familial amyloidotic polyneuropathy (FAP) (Met30), both fibre gastroscopy and colonoscopy studies were performed in FAP (Met30) patients. Microscopic changes were also examined in autopsied and biopsied materials from patients with FAP, and compared with data from autopsied samples from patients with AL amyloidosis, and secondary amyloidosis patients.

DESIGN

Endoscopic and histopathological study.

SETTING

Kumamoto University Hospital, Kumamoto, Japan.

SUBJECTS

Nine patients with FAP (Met30) underwent fibre gastroscopy and colonoscopy. Six autopsied and 23 biopsied gastrointestinal samples from FAP patients, four from autopsied amyloidosis (including two myeloma associated form), and two from autopsied secondary amyloidosis patients were examined for histopathological study.

MAIN OUTCOME MEASURES

Fibre gastroscopy and colonoscopy were employed for macroscopic study. Congo red and H-E staining were performed for histopathological study. Macroscopic changes in the gastrointestinal tract and microscopic differences in the amyloid distribution pattern were compared between the different types of amyloidosis.

RESULTS

Fibre gastroscopy and colonoscopy for nine FAP patients revealed that four showed a fine granular appearance in the duodenum, three showed lack of lustre, and two showed mucosal friability in the gastrointestinal tract; however, no macroscopic abnormality was observed in four other FAP patients. Histopathological examination of tissue from FAP patients revealed that, although a small amount of amyloid was recognized in the submucosa perivascular layer, a significant amount of amyloid was seen in and around the nerves of the gastrointestinal tract, but very little in Auerbach's nerve plexus. In total, the amount of deposited amyloid in the tissues was small compared with that in other types of systemic amyloidosis, such as AL and secondary amyloidosis.

CONCLUSION

These results suggest that the major reason why FAP patients show such severe gastrointestinal symptoms, compared with other types of systemic amyloidosis, may be because of the deposition of a significant amount of amyloid in the nerves in the gastrointestinal tract.

Familial amyloidosis: a study of 52 North American-born patients examined during a 30-year period

Between 1961 and 1990, 52 patients with biopsy-proven familial amyloidosis born in North America were examined at the Mayo Clinic. At the time of diagnosis of familial amyloidosis, 83% of these patients had peripheral neuropathy, 33% had autonomic neuropathy, and 27% had cardiomyopathy. Renal disease was noted in fewer than 10%, and liver involvement was rare. The median age at diagnosis was 64 years. The sensitivity of various diagnostic biopsies was similar to that for primary amyloidosis: deposits of amyloid were found in 77 and 78% of the subcutaneous fat aspirates or rectal biopsy specimens, respectively, and in 41% of specimens of bone marrow. The median duration of survival of 5.8 years for patients with inherited amyloidosis was superior to that for patients with primary amyloidosis. When patients were stratified by organ involvement, the survival of patients with familial amyloidosis remained superior. The presence of cardiomyopathy and an interactive variable of age and the presence of autonomic neuropathy were powerful predictors of survival. Of the 52 patients, 22 died, 12 (55%) of cardiac failure or cardiac arrhythmia. Nine patients (41%) died of inanition in conjunction with progressive peripheral or autonomic neuropathy. Transthyretin was identified by immunohistochemical studies in 31 of the 34 tissue specimens tested. A transthyretin mutation was identified in 24 of the 31. A transthyretin mutation was found in five additional patients for whom tissue was unavailable for immunostaining.

Bile acid malabsorption caused by gastrointestinal motility dysfunction? An investigation of gastrointestinal disturbances in familial amyloidosis with polyneuropathy

Gastrointestinal dysfunction due to autonomous neuropathy is a complication described in various diseases such as diabetes mellitus, multiple sclerosis, and familial amyloidosis with polyneuropathy. We present the results of a prospective investigation of bile acid malabsorption in 17 patients with familial amyloidosis by means of 75Se-labelled homocholic-tauro acid (SeHCAT). The diagnosis was in all cases verified by the DNA test for mutation of transthyretin in position 30. Small-intestinal biopsy specimens were examined for deposits of amyloid, and the presence of gastric retention was evaluated by gastroscopy. In addition, the patients were investigated for bacterial overgrowth by means of the bile acid breath test (BABT). A high frequency of abnormal BABT results (44%) was encountered. However, 65% also had abnormal low SeHCAT values, indicating bile acid malabsorption. Only two patients had abnormal BABT and normal SeHCAT results, indicating bacterial contamination of the small intestine. Bile acid losses increased with the duration of gastrointestinal symptoms. Significantly lower SeHCAT values were encountered in patients with gastric retention, whereas the occurrence of amyloid deposits in small-intestinal biopsy specimens was without effect on SeHCAT retention. Bile acid malabsorption is frequently encountered in familial amyloidosis with polyneuropathy and seems to be more closely associated with gastrointestinal motility dysfunction than with amyloid deposits in the intestinal mucosa.

Autonomic neuropathy in familial amyloidotic polyneuropathy. A clinical study based on heart rate variability

Familial amyloidotic polyneuropathy (FAP) is characterized by both sensimotor and autonomic dysfunction. Autonomic disturbance involving the gastrointestinal tract, the urinary bladder, the cardiac conduction system, and the peripheral circulation has been described. In this study simple, non-invasive tests of autonomic function based on heart rate variability were applied to 12 patients with FAP and 12 healthy volunteers. The heart rate variation during normal breathing, deep breathing and during tilt from recumbent to standing position was measured. All tests showed significantly less heart rate variation in patients than in controls and the heart rate variation decreased with increasing severity of neurological disability, but the small number of patients in our study does not allow any further comparison between subgroups. Our study thus indicates impaired cardiovascular autonomic function in patients with FAP and we believe that these findings might also be of importance in other forms of systemic amyloidosis.