Endoscopic Findings of Small-Bowel Lesions in Familial Amyloid Polyneuropathy: A Case Report

Characterization of Transthyretin Mutation G47V Associated with Hereditary Cardiac Amyloidosis

INTRODUCTION

Amyloidosis caused by TTR mutations (ATTRv) is a rare inherited and autosomal dominant disease. More than 150 mutants of TTR have been reported, whereas some of them remain to be investigated.

METHODS

A 52-year-old male presented with heart failure and clinically diagnosed ATTR cardiac amyloidosis (ATTR-CA) was recruited. Whole-exome sequencing (WES) was performed. Biochemical and biophysical experiments characterized protein stability using urea-mediated tryptophan fluorescence. Drug response was analyzed by fibril formation assay. Finally, tetramer TTR concentration in patient's serum sample was measured by ultra-performance liquid chromatography (UPLC).

RESULTS

For the proband, WES revealed a mutation (c.200G>T; p.Gly67Val and referred to as G47V) in TTR gene. Biochemical and biophysical kinetics study showed that the thermodynamic stability of G47V-TTR (Cm = 2.4 m) was significantly lower than that of WT-TTR (Cm = 3.4 m) and comparable to that of L55P-TTR (Cm = 2.3 m), an early age-of-onset mutation. G47V:WT-TTR heterozygous tetramer kinetic stability (t1/2 = 1.4 h) was further compromised compared to that of the homozygous G47V-TTR (t1/2 = 3.1 h). Among three small molecule stabilizers, AG10 exhibited the best inhibition of the fibrillation of G47V-TTR homozygous protein. Using a UPLC assay, nearly 40% of TTR in this patient was calculated to be non-tetrameric.

CONCLUSION

In this work, we reported a patient presented early onset of clinically typical ATTR-CA due to G47V-TTR mutation. Our work for the first time not only characterized the biochemical properties of G47V-TTR mutation, but also provided hints for the pathogenicity of this mutation.

Primary amyloidosis involving the gastrointestinal tract, mesentery and omentum: A case report

Amyloidosis, a systemic disease characterized by the deposition of misfolded protein, is difficult to rapidly diagnose due to its wide range of symptoms. The present study reported on a case of primary amyloidosis (AL) with involvement of the gastrointestinal tract, mesentery and omentum in a 66-year-old male presenting with recurrent diarrhoea and abdominal distension. Oesophagogastroduodenoscopy and enteroscopy revealed multiple gastric ulcers and multiple protuberant lesions in the colon. Laparotomy indicated multiple nodules in the mesentery of the small intestine. Contrast-enhanced CT revealed dilation of the small bowel with pneumatosis intestinalis and positive Congo red staining of gastric mucosa and mesentery biopsy specimens confirmed amyloid deposition. Therefore, the patient was diagnosed with AL. In this case, the clinical manifestation of mesentery amyloidosis was multiple nodules and extensive peritoneal adhesions, which, to the best of our knowledge, has not been reported by any previous study.

Hereditary transthyretin amyloidosis in multi-ethnic Malaysians

We report the clinical and genetic characteristics of hereditary transthyretin amyloidosis in the multi-ethnic Malaysian population. Subjects with genetically confirmed transthyretin amyloidosis seen between 2001 till August 2020 were included. There were 30 patients and 14 asymptomatic carriers, of which 26 (59.1%) were men. The majority (86.7%) were ethnic Chinese while two (6.7%) each were Malay and Sri Lankan Tamil ethnicity respectively. Among patients, mean age of symptom-onset was 55.9 ± 9.8 years with mean duration from symptom-onset to diagnosis of 3.2 ± 2.5 years. Common presenting symptoms were sensory symptoms of upper limbs (43.3%), symmetric sensory symptoms of both lower limbs (16.7%) and autonomic symptoms (16.7%). Nerve conduction studies showed sensorimotor polyneuropathy in 25 (83.3%) patients (22, axonal). Abnormal echocardiograms were seen in 24 (80%) patients, although 15 were asymptomatic. Of six different TTR mutations found, Ala97Ser was the commonest, and found exclusively in 84.6% of Chinese patients. Other mutations among Chinese patients were Val30Met, Ala25Thr and Asp39Val. Our Malay and Tamil patients had Glu54Lys and Gly47Val mutations respectively. In conclusion, TTR Ala97Ser is the commonest mutation among ethnic Chinese Malaysians which presented with late-onset progressive sensorimotor polyneuropathy, autonomic dysfunction and subclinical cardiac involvement.

Orthostatic hypotension in hereditary transthyretin amyloidosis: epidemiology, diagnosis and management

Purpose

Neurogenic orthostatic hypotension is a prominent and disabling manifestation of autonomic dysfunction in patients with hereditary transthyretin (TTR) amyloidosis affecting an estimated 40–60% of patients, and reducing their quality of life. We reviewed the epidemiology and pathophysiology of neurogenic orthostatic hypotension in patients with hereditary TTR amyloidosis, summarize non-pharmacologic and pharmacological treatment strategies and discuss the impact of novel disease-modifying treatments such as transthyretin stabilizers (diflunisal, tafamidis) and RNA interference agents (patisiran, inotersen).

Methods

Literature review.

Results

Orthostatic hypotension in patients with hereditary transthyretin amyloidosis can be a consequence of heart failure due to amyloid cardiomyopathy or volume depletion due to diarrhea or drug effects. When none of these circumstances are apparent, orthostatic hypotension is usually neurogenic, i.e., caused by impaired norepinephrine release from sympathetic postganglionic neurons, because of neuronal amyloid fibril deposition.

Conclusions

When recognized, neurogenic orthostatic hypotension can be treated. Discontinuation of potentially aggravating medications, patient education and non-pharmacologic approaches should be applied first. Droxidopa (Northera^®), a synthetic norepinephrine precursor, has shown efficacy in controlled trials of neurogenic orthostatic hypotension in patients with hereditary TTR amyloidosis and is now approved in the US and Asia. Although they may be useful to ameliorate autonomic dysfunction in hereditary TTR amyloidosis, the impact of disease-modifying treatments on neurogenic orthostatic hypotension is still uninvestigated.

Small Bowel Amyloidosis

PURPOSE OF REVIEW

The goal of this paper is to review the literature on small bowel amyloidosis. Our review focuses on the underlying etiology, histopathology, clinical features, endoscopic and radiologic findings, and the mainstay of management.

RECENT FINDINGS

The latest research shows changing epidemiological trends of different types of amyloidosis. It also reveals a better understanding of its pathophysiology and shows improvement in treatment outcomes. Amyloidosis is a group of diseases of multiple etiologies and clinical presentations. It is characterized by pathological deposition of insoluble fibrillar proteins within various organs leading to disruption of their structure and function. The classification of amyloidosis includes primary, secondary, dialysis-related, senile, and hereditary. Amyloidosis can be systemic or localized. The incidence of AA amyloidosis is declining in frequency. If the gastrointestinal (GI) tract is involved, the small intestine is the most commonly affected site. Overall, outcomes among patients with newly diagnosed amyloidosis have improved. This article focuses on small bowel amyloidosis.

Systemic amyloidosis with gastrointestinal involvement: Diagnosis from endoscopic and histological views

Amyloid tends to deposit in the gastrointestinal tract, which, being easily accessible, is often the target organ for a pathological diagnostic examination. Although a mucosal biopsy is necessary for a definitive diagnosis and several studies have reported positive results for each possible biopsy site, there remain many unclear features in various aspects. This review focuses on the current literature to determine a better understanding of the diagnosis from endoscopic and histological views in patients with systemic amyloidosis with gastrointestinal involvement. A literature search was performed using PubMed to identify relevant studies; linked references were also reviewed. Endoscopic findings vary based on the organ and the depositing amyloids. A fine granular appearance or polypoid protrusions are likely to occur in the duodenum. AL, Aβ2M, and ATTR amyloids are likely to deposit submucosally, while AA amyloid is easily deposited in the superficial layer of the mucous membrane. Furthermore, it is necessary to consider the collection of biopsy specimens from the duodenum, which has high positive biopsy rates. However, the difference in the positive biopsy rates depends on whether endoscopic findings are available or whether the appropriate number has not been fully elucidated. A duodenal biopsy is strongly recommended to confirm the deposition of amyloid in patients with systemic amyloidosis having gastrointestinal involvement. Because amyloidosis is a disease with a poor prognosis, early diagnosis and treatment are required; gastroenterologists and endoscopists play important roles.