Autonomic nervous system and cardiac involvement in familial amyloidosis, Finnish type (FAF)

Hereditary gelsolin amyloidosis: a rare cause of cranial, peripheral and autonomic neuropathies linked to D187N and Y447H substitutions

INTRODUCTION

Hereditary gelsolin (AGel) amyloidosis is a systemic disease that is characterised by neurologic, ophthalmologic, dermatologic, and other organ involvements. We describe the clinical features with a focus on neurological manifestations in a cohort of patients with AGel amyloidosis referred to the Amyloidosis Centre in the United States.

METHODS

Fifteen patients with AGel amyloidosis were included in the study between 2005 and 2022 with the permission of the Institutional Review Board. Data were collected from the prospectively maintained clinical database, electronic medical records and telephone interviews.

RESULTS

Neurologic manifestations were featured in 15 patients: cranial neuropathy in 93%, peripheral and autonomic neuropathy in 57% and bilateral carpal tunnel syndrome in 73% of cases. A novel p.Y474H gelsolin variant featured a unique clinical phenotype that differed from the one associated with the most common variant of AGel amyloidosis.

DISCUSSION

We report high rates of cranial and peripheral neuropathy, carpal tunnel syndrome and autonomic dysfunction in patients with systemic AGel amyloidosis. The awareness of these features will enable earlier diagnosis and timely screening for end-organ dysfunction. The characterisation of pathophysiology will assist the development of therapeutic options in AGel amyloidosis.

Hearing problems in patients with hereditary gelsolin amyloidosis

BACKGROUND

Gelsolin amyloidosis (AGel amyloidosis) is a hereditary form of systemic amyloidosis featuring ophthalmological, neurological and cutaneous symptoms. Previous studies based mainly on patients' self-reporting have indicated that hearing impairment might also be related to the disease, considering the progressive cranial neuropathy characteristic for AGel amyloidosis. In order to deepen the knowledge of possible AGel amyloidosis-related hearing problems, a clinical study consisting of the Speech, Spatial and Qualities of Hearing Scale (SSQ) questionnaire, clinical examination, automated pure-tone audiometry and a speech-in-noise test was designed.

RESULTS

Of the total 46 patients included in the study, eighteen (39%) had self-reported hearing loss. The mean scores in the SSQ were 8.2, 8.3 and 8.6 for the Speech, Spatial and Qualities subscales, respectively. In audiometry, the mean pure tone average (PTA) was 17.1 (SD 12.2) and 17.1 (SD 12.3) dB HL for the right and left ears, respectively, with no difference to gender- and age-matched, otologically normal reference values. The average speech reception threshold in noise (SRT) was - 8.2 (SD 1.5) and - 8.0 (SD 1.7) dB SNR for the right and left ears, respectively, which did not differ from a control group with a comparable range in PTA thresholds.

CONCLUSION

Although a significant proportion of AGel amyloidosis patients experience subjective difficulties in hearing there seems to be no peripheral or central hearing impairment at least in patients up to the age of 60 years.

Cardiac manifestations in Finnish gelsolin amyloidosis patients

INTRODUCTION

Finnish gelsolin amyloidosis (AGel amyloidosis) is an inherited systemic amyloidosis with well-known ophthalmological, neurological and cutaneous symptoms. Additionally, cardiomyopathies, conduction disorders and need of cardiac pacemakers occur in some patients. This study focuses on electrocardiographic (ECG) findings in AGel amyloidosis and their relation to cardiac magnetic resonance (CMR) changes. We also assessed whether ECG abnormalities were associated with pacemaker implantation and mortality.

MATERIALS AND METHODS

In this cohort study, 51 genetically verified AGel amyloidosis patients (mean age 66 years) without cardiac pacemakers underwent 12-lead ECG and CMR imaging with contrast agent in 2017. Patients were followed-up for 3 years.

RESULTS

Conduction disturbances were found in 22 patients (43%). Nine (18%) presented with first-degree atrioventricular block, six (12%) with left anterior hemiblock, seven (14%) with left or right bundle branch block and two (4%) with non-specific intraventricular conduction delay. Low QRS voltage was present in two (4%) patients. Late gadolinium enhancement (LGE) concentrating on the interventricular septum and inferior parts of the heart was present in 19 (86%) patients with conduction abnormalities. During the follow-up, only one patient received a pacemaker, and one patient died.

DISCUSSION

Conduction disorders and septal LGE are common in AGel amyloidosis, whereas other ECG and CMR findings typically observed in most common cardiac amyloidosis types were rare. Septal pathology seen in CMR may interfere with the cardiac conduction system in AGel amyloidosis, explaining conduction disorders, although pacemaker therapy is rarely required.

Neuromuscular amyloidosis: Unmasking the master of disguise

Amyloidosis refers to an etiologically heterogeneous group of protein misfolding diseases, pathologically characterized by extracellular amyloid fibrils producing congophillic amorphous deposits in organs and tissues, which may lead to severe organ dysfunction and mortality. Clinical presentations vary and are often nonspecific, depending on what organs or tissues are affected. In systemic amyloidosis, the peripheral nervous system is commonly affected, whereas the skeletal muscles are only rarely involved. Immunoglobulin light chain (AL) amyloidosis and hereditary transthyretin (ATTRv) amyloidosis are the most frequent types of systemic amyloidosis involving the neuromuscular system. Localized amyloidosis can occur in skeletal muscle, so-called isolated amyloid myopathy. Amyloid neuropathy typically involves small myelinated and unmyelinated sensory and autonomic nerve fibers early in the course of the disease, followed by large myelinated fiber sensory and motor deficits. The relentlessly progressive nature with motor, painful sensory and severe autonomic dysfunction, profound weight loss, and systemic features are distinct characteristics of amyloid neuropathy. Amyloid myopathy presentation differs between systemic amyloidosis and isolated amyloid myopathy. Long-standing symptoms, distal predominant myopathy, markedly elevated creatine kinase level, and lack of peripheral neuropathy or systemic features are highly suggestive of isolated amyloid myopathy. In ATTR and AL amyloidosis, early treatment correlates with favorable outcomes. Therefore, awareness of these disorders and active screening for amyloidosis in patients with neuropathy or myopathy are crucial in detecting these patients in the everyday practice of neuromuscular medicine. Herein, we review the clinical manifestations of neuromuscular amyloidosis and provide a diagnostic approach to this disorder.

Finnish gelsolin amyloidosis causes significant disease burden but does not affect survival: FIN-GAR phase II study

BACKGROUND

Hereditary gelsolin (AGel) amyloidosis is an autosomal dominantly inherited systemic amyloidosis that manifests with the characteristic triad of progressive ophthalmological, neurological and dermatological signs and symptoms. The National Finnish Gelsolin Amyloidosis Registry (FIN-GAR) was founded in 2013 to collect clinical data on patients with AGel amyloidosis, including altogether approximately one third of the Finnish patients. We aim to deepen knowledge on the disease burden and life span of the patients using data from the updated FIN-GAR registry. We sent an updated questionnaire concerning the symptoms and signs, symptomatic treatments and subjective perception on disease progression to 240 members of the Finnish Amyloidosis Association (SAMY). We analyzed the lifespan of 478 patients using the relative survival (RS) framework.

RESULTS

The updated FIN-GAR registry includes 261 patients. Symptoms and signs corresponding to the classical triad of ophthalmological (dry eyes in 93%; corneal lattice amyloidosis in 89%), neurological (numbness, tingling and other paresthesias in 75%; facial paresis in 67%), and dermatological (drooping eyelids in 86%; cutis laxa in 84%) manifestations were highly prevalent. Cardiac arrhythmias were reported by 15% of the patients and 5% had a cardiac pacemaker installed. Proteinuria was reported by 13% and renal failure by 5% of the patients. A total of 65% of the patients had undergone a skin or soft tissue surgery, 26% carpal tunnel surgery and 24% at least unilateral cataract surgery. As regards life span, relative survival estimates exceeded 1 for males and females until the age group of 70-74 years, for which it was 0.96.

CONCLUSIONS

AGel amyloidosis causes a wide variety of ophthalmological, neurological, cutaneous, and oral symptoms that together with repeated surgeries cause a clinically significant disease burden. Severe renal and cardiac manifestations are rare as compared to other systemic amyloidoses, explaining in part the finding that AGel amyloidosis does not shorten the life span of the patients at least for the first 75 years.

Amyloid in parenchymal organs in gelsolin (AGel) amyloidosis

Objectives: Previous clinical studies have shown frequent cardiac symptoms in patients with hereditary gelsolin (AGel) amyloidosis, possibly related to amyloid deposition in the heart and other internal organs. Previous studies on internal organ amyloid deposition in AGel amyloidosis have been based on small patient series. Methods: Paraffin-embedded tissue sections from 25 autopsied individuals (age at death 44.4-88.6 years) with AGel amyloidosis were stained with HE, Congo red and Herovici stains and immunohistochemistry against the low molecular weight gelsolin fraction was performed. The amount of amyloid was estimated semi-quantitatively. Results: AGel-based amyloid deposits were found in the myocardium and cardiac blood vessels in every patient. The deposits were mainly small and co-localized with regions with excess fibrosis in the myocardium. The lungs were positive for amyloid in 79%, renal parenchyma in 54% and renal blood vessels in 71% of the cases. The amount of myocardial, renal and hepatic amyloid correlated with age at death of the patients. Conclusions: We show the constant presence of AGel amyloid in the hearts of patients with AGel amyloidosis. Although the deposits were mainly small, the co-localization of amyloid with fibrosis may amplify the effect of pure amyloid deposition, possibly leading to clinical signs and symptoms.

High-resolution crystal structure of gelsolin domain 2 in complex with the physiological calcium ion

The second domain of gelsolin (G2) hosts mutations responsible for a hereditary form of amyloidosis. The active form of gelsolin is Ca²⁺-bound; it is also a dynamic protein, hence structural biologists often rely on the study of the isolated G2. However, the wild type G2 structure that have been used so far in comparative studies is bound to a crystallographic Cd²⁺, in lieu of the physiological calcium. Here, we report the wild type structure of G2 in complex with Ca²⁺ highlighting subtle ion-dependent differences. Previous findings on different G2 mutations are also briefly revised in light of these results.

The role of gelsolin domain 3 in familial amyloidosis (Finnish type)

In the disease familial amyloidosis, Finnish type (FAF) the mechanism by which point mutations in gelsolin domain 2 (G2) lead to furin cleavage is not understood for the intact protein. Here, we determine that FAF mutants adopt similar conformations to the wild-type protein. However, the mutations appear to affect the dynamics of domain:domain interactions. Thus, proper domain:domain interactions are needed to protect G2 from protease cleavage. We make mutations in the following domain (G3) that functionally mimic the FAF mutations in G2. We conclude that G2 is on the limits of stability, and perturbations that affect domain:domain stabilizing interactions tip the balance toward cleavage. These data explain how multiple FAF mutations give rise to amyloid formation.

In the disease familial amyloidosis, Finnish type (FAF), also known as AGel amyloidosis (AGel), the mechanism by which point mutations in the calcium-regulated actin-severing protein gelsolin lead to furin cleavage is not understood in the intact protein. Here, we provide a structural and biochemical characterization of the FAF variants. X-ray crystallography structures of the FAF mutant gelsolins demonstrate that the mutations do not significantly disrupt the calcium-free conformations of gelsolin. Small-angle X-ray–scattering (SAXS) studies indicate that the FAF calcium-binding site mutants are slower to activate, whereas G167R is as efficient as the wild type. Actin-regulating studies of the gelsolins at the furin cleavage pH (6.5) show that the mutant gelsolins are functional, suggesting that they also adopt relatively normal active conformations. Deletion of gelsolin domains leads to sensitization to furin cleavage, and nanobody-binding protects against furin cleavage. These data indicate instability in the second domain of gelsolin (G2), since loss or gain of G2-stabilizing interactions impacts the efficiency of cleavage by furin. To demonstrate this principle, we engineered non-FAF mutations in G3 that disrupt the G2-G3 interface in the calcium-activated structure. These mutants led to increased furin cleavage. We carried out molecular dynamics (MD) simulations on the FAF and non-FAF mutant G2-G3 fragments of gelsolin. All mutants showed an increase in the distance between the center of masses of the 2 domains (G2 and G3). Since G3 covers the furin cleavage site on G2 in calcium-activated gelsolin, this suggests that destabilization of this interface is a critical step in cleavage.

Gelsolin amyloid angiopathy causes severe disruption of the arterial wall

Hereditary gelsolin amyloidosis (HGA) is a dominantly inherited systemic disease reported worldwide. HGA is characterized by ophthalmological, neurological, and dermatological manifestations. AGel amyloid accumulates at basal lamina of epithelial and muscle cells, thus amyloid angiopathy is encountered in nearly every organ. HGA patients have cardiovascular, hemorrhagic, and potentially vascularly induced neurological problems. To clarify pathomechanisms of AGel angiopathy, we performed histological, immunohistochemical, and electron microscopic analyses on facial temporal artery branches from 8 HGA patients and 13 control subjects. We demonstrate major pathological changes in arteries: disruption of the tunica media, disorganization of vascular smooth muscle cells, and accumulation of AGel fibrils in arterial walls, where they associate with the lamina elastica interna, which becomes fragmented and diminished. We also provide evidence of abnormal accumulation and localization of collagen types I and III and an increase of collagen type I degradation product in the tunica media. Vascular smooth muscle cells appear to be morphologically and semi-quantitatively normal, only their basal lamina is often thickened. In conclusion, angiopathy in HGA results in severe disruption of arterial walls, characterized by prominent AGel deposition, collagen derangement and severe elastolysis, and it may be responsible for several, particularly hemorrhagic, disease manifestations in HGA.

Progressive cranial nerve involvement and grading of facial paralysis in gelsolin amyloidosis

INTRODUCTION

Hereditary gelsolin amyloidosis (GA) is a rare condition caused by the gelsolin gene mutation. The diagnostic triad includes corneal lattice dystrophy (type 2), progressive bilateral facial paralysis, and cutis laxa. Detailed information on facial paralysis in GA and the extent of cranial nerve injury is lacking.

METHODS

29 GA patients undergoing facial corrective surgery were interviewed, examined, and studied electroneurophysiologically.

RESULTS

All showed dysfunction of facial (VII) and trigeminal (V) nerves, two-thirds of oculomotor (III) and hypoglossal (XII) nerves, and half of vestibulocochlear (acoustic) (VIII) nerve. Clinical involvement of frontal, zygomatic, and buccal facial nerve branches was seen in 97%, 83%, and 52% of patients, respectively. Electromyography showed marked motor unit potential loss in facial musculature.

CONCLUSIONS

Cranial nerve involvement in GA is more widespread than previously described, and correlates with age, severity of facial paralysis, and electromyographic findings. We describe a grading method for bilateral facial paralysis in GA, which is essential for evaluation of disease progression and the need for treatment.

Hereditary gelsolin amyloidosis

Hereditary gelsolin amyloidosis (HGA) is an autosomally dominantly inherited form of systemic amyloidosis, characterized mainly by cranial and sensory peripheral neuropathy, corneal lattice dystrophy, and cutis laxa. HGA, originally reported from Finland and now increasingly from other countries in Europe, North and South America, and Asia, may still be underdiagnosed worldwide. It is the first and so-far only known disorder caused by a gelsolin gene defect, namely a G654A or G654T mutation. Gelsolin is a principal actin-modulating protein, implicated in multiple biological processes, also in the nervous system, e.g. axonal transport, myelination, neurite outgrowth, and neuroprotection. The gelsolin gene defect causes expression of variant gelsolin, followed by systemic deposition of gelsolin amyloid (AGel) in HGA patients and even other consequences on the metabolism and function of gelsolin. In HGA, specific therapy is not yet available but correct diagnosis enables adequate symptomatic treatment which decisively improves the quality of life in these patients. A transgenic murine model of HGA expressing AGel is available, in anticipation of new treatment options targeted toward this slowly progressive but devastating amyloidosis. Present and future lessons learned from HGA may be applicable even in diagnosis and treatment of other hereditary and sporadic amyloidoses.

Familial amyloidotic polyneuropathy type IV--gelsolin amyloidosis

Familial amyloidotic polyneuropathy type IV, or Gelsolin amyloidosis (GA), is a rare condition caused by G654A or G654T mutation in gelsolin gene at 9q32-34. Gelsolin seems essential in many processes, including inflammation, cell motility, neural recovery, apoptosis and even carcinogenesis. So far reported from many European countries, USA, Japan, Iran and Brazil, GA is probably still underdiagnosed. The typical diagnostic triad includes corneal lattice dystrophy, progressive bilateral facial paralysis and cutis laxa. Patients present with progressive cranial and peripheral neuropathy, eye symptoms, usually mild proteinuria, and cardiac conductive disturbances with age. Central nervous system symptoms are rare. Gelsolin amyloid collection in tissues is widespread. To date, treatment is symptomatic. Regular check-ups with ophthalmologist are recommended. Plastic surgery relieves the functional symptoms caused by facial paralysis and loose, hanging facial skin.

Gelsolin amyloidosis: genetics, biochemistry, pathology and possible strategies for therapeutic intervention

Protein misassembly into aggregate structures, including cross-β-sheet amyloid fibrils, is linked to diseases characterized by the degeneration of post-mitotic tissue. While amyloid fibril deposition in the extracellular space certainly disrupts cellular and tissue architecture late in the course of amyloid diseases, strong genetic, pathological and pharmacologic evidence suggests that the process of amyloid fibril formation itself, known as amyloidogenesis, likely causes these maladies. It seems that the formation of oligomeric aggregates during the amyloidogenesis process causes the proteotoxicity and cytotoxicity characteristic of these disorders. Herein, we review what is known about the genetics, biochemistry and pathology of familial amyloidosis of Finnish type (FAF) or gelsolin amyloidosis. Briefly, autosomal dominant D187N or D187Y mutations compromise Ca(2+) binding in domain 2 of gelsolin, allowing domain 2 to sample unfolded conformations. When domain 2 is unfolded, gelsolin is subject to aberrant furin endoproteolysis as it passes through the Golgi on its way to the extracellular space. The resulting C-terminal 68 kDa fragment (C68) is susceptible to extracellular endoproteolytic events, possibly mediated by a matrix metalloprotease, affording 8 and 5 kDa amyloidogenic fragments of gelsolin. These amyloidogenic fragments deposit systemically, causing a variety of symptoms including corneal lattice dystrophy and neurodegeneration. The first murine model of the disease recapitulates the aberrant processing of mutant plasma gelsolin, amyloid deposition, and the degenerative phenotype. We use what we have learned from our biochemical studies, as well as insight from mouse and human pathology to propose therapeutic strategies that may halt the progression of FAF.

Heparin binds 8 kDa gelsolin cross-β-sheet oligomers and accelerates amyloidogenesis by hastening fibril extension

Glycosaminoglycans (GAGs) are highly sulfated linear polysaccharides prevalent in the extracellular matrix, and they associate with virtually all amyloid deposits in vivo. GAGs accelerate the aggregation of many amyloidogenic peptides in vitro, but little mechanistic evidence is available to explain why. Herein, spectroscopic methods demonstrate that GAGs do not affect the secondary structure of the monomeric 8 kDa amyloidogenic fragment of human plasma gelsolin. Moreover, monomerized 8 kDa gelsolin does not bind to heparin under physiological conditions. In contrast, 8 kDa gelsolin cross-β-sheet oligomers and amyloid fibrils bind strongly to heparin, apparently because of electrostatic interactions between the negatively charged polysaccharide and a positively charged region of the 8 kDa gelsolin assemblies. Our observations are consistent with a scaffolding mechanism whereby cross-β-sheet oligomers, upon formation, bind to GAGs, accelerating the fibril extension phase of amyloidogenesis, possibly by concentrating and orienting the oligomers to more efficiently form amyloid fibrils. Notably, heparin decreases the 8 kDa gelsolin concentration necessary for amyloid fibril formation, likely a consequence of fibril stabilization through heparin binding. Because GAG overexpression, which is common in amyloidosis, may represent a strategy for minimizing cross-β-sheet oligomer toxicity by transforming them into amyloid fibrils, the mechanism described herein for GAG-mediated acceleration of 8 kDa gelsolin amyloidogenesis provides a starting point for therapeutic strategy development. The addition of GAG mimetics, small molecule sulfonates shown to reduce the amyloid load in animal models of amyloidosis, to a heparin-accelerated 8 kDa gelsolin aggregation reaction mixture neither significantly alters the rate of amyloidogenesis nor prevents oligomers from binding to GAGs, calling into question their commonly accepted mechanism.

Hereditary amyloidosis of the Finnish type in a German family: clinical and electrophysiological presentation

Hereditary amyloidosis of the Finnish type (HAF, or familial amyloid polyneuropathy type IV) is an autosomal dominant disease that has been described most commonly in the Finnish population but has also been found in some other countries. Herein we report the first German family whose members suffer from this condition. There are no known Finnish ancestors. We performed clinical and electrophysiological examinations in 22 members of this family. All symptomatic family members suffered from facial palsy, and most of them had peripheral neuropathy. One patient had confirmed corneal lattice dystrophy. Additional symptoms were hypoglossal nerve involvement in 5 patients and oculomotor nerve palsy in 1 patient. The lips of all older patients appeared thickened. The causative G654A mutation in the gelsolin gene was found in all affected family members.

The neuromuscular manifestations of amyloidosis

Amyloidosis is a systemic disease that may be acquired or hereditary and which results in the deposition of amyloid fibrils in a variety of tissues causing their progressive dysfunction. Although the clinical presentation often is dominated by cardiac or renal failure, peripheral neuropathy may be a significant or the initial manifestation, resulting in presentation to the neurologist. Diagnosis often is challenging and may require multiple diagnostic procedures, including more than one biopsy. Acquired and hereditary amyloidosis can be definitively distinguished from one another only by immunohistochemical staining or molecular genetic testing. Treatment remains a challenge, although chemotherapy and autologous stem cell transplantation offer hope for those with primary systemic amyloidosis, whereas liver transplantation is effective for some forms of hereditary amyloid neuropathy. Much less commonly, myopathy may be a clinically significant manifestation of amyloidosis.

The 8 and 5 kDa fragments of plasma gelsolin form amyloid fibrils by a nucleated polymerization mechanism, while the 68 kDa fragment is not amyloidogenic

Familial amyloidosis of Finnish type (FAF), or gelsolin amyloidosis, is a systemic amyloid disease caused by a mutation (D187N/Y) in domain 2 of human plasma gelsolin, resulting in domain 2 misfolding within the secretory pathway. When D187N/Y gelsolin passes through the Golgi, furin endoproteolysis within domain 2 occurs as a consequence of the abnormal conformations that enable furin to bind and cleave, resulting in the secretion of a 68 kDa C-terminal fragment (amino acids 173-755, C68). The C68 fragment is cleaved upon secretion from the cell by membrane type 1 matrix metalloprotease (MT1-MMP), affording the 8 and 5 kDa fragments (amino acids 173-242 and 173-225, respectively) comprising the amyloid fibrils in FAF patients. Herein, we show that the 8 and 5 kDa gelsolin fragments form amyloid fibrils by a nucleated polymerization mechanism. In addition to demonstrating the expected concentration dependence of a nucleated polymerization reaction, the addition of preformed amyloid fibrils, or "seeds", was shown to bypass the requirement for the formation of a high-energy nucleus, accelerating 8 and 5 kDa D187N gelsolin amyloidogenesis. The C68 fragment can form small oligomers, but not amyloid fibrils, even when seeded with preformed 8 kDa fragment plasma gelsolin fibrils. Because the 68 kDa fragment of gelsolin does not form amyloid fibrils in vitro or in a recently published transgenic mouse model of FAF, we propose that administration of an MT1-MMP inhibitor could be an effective strategy for the treatment of FAF.

Patterns of neuropathy and autonomic failure in patients with amyloidosis

OBJECTIVE

To define the clinical patterns of peripheral neuropathy and autonomic testing abnormalities in patients with amyloidosis.

PATIENTS AND METHODS

A retrospective chart review was conducted of 65 patients who had biopsy-proven amyloidosis and autonomic function testing between January 1, 1985, and December 31, 1997, at Mayo Clinic's site in Rochester, MN. Patients were required to have neurologic evaluation, autonomic reflex screening, and tissue confirmation of amyloidosis.

RESULTS

We identified 5 clinical patterns of peripheral neuropathy: (1) generalized autonomic failure and polyneuropathy with pain (40 patients [62%]), (2) generalized autonomic failure and polyneuropathy without pain (11 [17%]), (3) isolated generalized autonomic failure (7 [11%]), (4) polyneuropathy without generalized autonomic failure (4 [6%]), and (5) generalized autonomic failure and small-fiber (ie, autonomic and somatic C-fiber) neuropathy (3 [5%]). Moderately severe generalized autonomic failure, involving adrenergic, cardiovagal, or sudomotor domains, was found in all patients, including those without clinically manifested autonomic failure. The diagnosis of amyloidosis was delayed in patients who did not have initial symptoms of pain or generalized autonomic failure (48 months to diagnosis in patients with polyneuropathy without autonomic failure vs 12 months to diagnosis in patients with autonomic failure and small-fiber neuropathy; P=.57).

CONCLUSION

Physicians should test for symptoms of generalized autonomic failure in patients who have peripheral neuropathy of unknown origin. Autonomic testing may give abnormal results in patients without overt symptoms of autonomic failure. Early recognition of autonomic failure may lead to earlier diagnosis of the underlying pathogenesis of amyloidosis, as well as earlier treatment for patients with this condition.

Familial amyloid polyneuropathy (Finnish type) in a Japanese family: Clinical features and immunocytochemical studies

Familial amyloid polyneuropathy (FAP: type IV), known as familial amyloidosis of the Finnish type (FAF), is very rare and reported only in a few countries. The gelsolin mutation G654A is most frequent causative gene in FAF family. The clinical phenotype of FAF possesses several neurological characteristics with multiple cranial nerve signs, in addition to a peculiar exanthema of "lichen amyloidosus" and pendulous skin "cutis laxa", and the carpal tunnel syndrome. We report a new Japanese FAF family presenting bilateral atrophies and fasciculations of the facial muscles and tongue. The patients in our family presented with skin changes as "lichen amyloidosus" and "cutis laxa". In this FAF family, lichen amyloidosus appeared under sunlight and high temperatures in the summer season every year. Two patients in our family presented with common clinical features of FAF, except for the above laboratory results. Including previous cases and our family, this clinical phenotype is similar to the gelsolin gene mutation (G654A) in FAF family members.

Sporadic and familial cerebral amyloid angiopathies

Cerebral amyloid angiopathy (CAA) is the term used to describe deposition of amyloid in the walls of arteries, arterioles and, less often, capillaries and veins of the central nervous system. CAAs are an important cause of cerebral hemorrhage and may also result in ischemic lesions and dementia. A number of amyloid proteins are known to cause CAA. The most common sporadic CAA, caused by A beta deposition, is associated with aging and is a common feature of Alzheimer disease (AD). CAA occurs in several familial conditions, including hereditary cerebral hemorrhage with amyloidosis of Icelandic type caused by deposition of mutant cystatin C, hereditary cerebral hemorrhage with amyloidosis Dutch type and familial AD with deposition of either A beta variants or wild-type A beta, the transthyretin-related meningo-vascular amyloidoses, gelsolin as well as familial prion disease-related CAAs and the recently described BRI2 gene-related CAAs in familial British dementia and familial Danish dementia. This review focuses on the morphological, biochemical, and genetic aspects as well as the clinical significance of CAAs with special emphasis on the BRI2 gene-related cerebrovascular amyloidoses. We also discuss data relevant to the pathomechanism of the different forms of CAA with an emphasis on the most common A beta-related types.

Autonomic peripheral neuropathy

The autonomic neuropathies are a group of disorders in which the small, lightly myelinated and unmyelinated autonomic nerve fibres are selectively targeted. Autonomic features, which involve the cardiovascular, gastrointestinal, urogenital, sudomotor, and pupillomotor systems, occur in varying combination in these disorders. Diabetes is the most common cause of autonomic neuropathy in more developed countries. Autonomic neuropathies can also occur as a result of amyloid deposition, after acute infection, as part of a paraneoplastic syndrome, and after exposure to neurotoxins including therapeutic drugs. Certain antibodies (eg, anti-Hu and those directed against neuronal nicotinic acetylcholine receptor) are associated with autonomic signs and symptoms. There are several familial autonomic neuropathies with autosomal dominant, autosomal recessive, or X-linked patterns of inheritance. Autonomic dysfunction can occur in association with specific infections. The availability of sensitive and reproducible measures of autonomic function has improved physicians' ability to diagnose these disorders.

Cardiac conduction alterations in a French family with amyloidosis of the finnish type with the p.Asp187Tyr mutation in theGSN gene

Familial amyloidosis of the Finnish type (FAF) is a rare autosomal-dominant disorder caused by the accumulation of a 71-amino acid amyloidogenic fragment of mutant gelsolin, an actin-modulating protein. The main symptoms include corneal lattice dystrophy, progressive cranial and peripheral neuropathy, and skin changes. To date, only two mutations in the GSN gene have been described: the p.Asp187Asn mutation in most patients and the p.Asp187Tyr mutation in a Danish and Czech family. We report on the third family with the p.Asp187Tyr mutation and the first French FAF family. Severe cardiac conduction alterations in three patients were mainly caused by cardiac sympathetic denervation. These findings demonstrate the cardiological involvement of the FAF phenotype and suggest that cardiological follow-up is required in FAF patients.

Gelsolin-related familial amyloidosis, Finnish type, in a Portuguese family: Clinical and neurophysiological studies

We report a Portuguese family with familial amyloid polyneuropathy related to gelsolin. There were no known Finnish ancestors, but the same mutation as described in Finnish patients (G654A) was carried. Clinical and neurophysiological investigations were performed in four patients. Corneal lattice dystrophy affected all four patients; an axonal lesion of the facial nerve occurred in three patients; visual tract involvement was documented in one case; and corticospinal and posterior column dysfunction was present in one patient. Polarizing microscopy of skin and muscle samples demonstrated amyloid deposits in two patients; anti-gelsolin immunohistochemistry was positive for amyloidogenic gelsolin. The Finnish mutation of gelsolin protein (G654A) was detected in five family members. The utility of neurophysiological testing in the evaluation and follow-up of this type of amyloidosis is discussed.

Autonomic dysfunction in peripheral nerve disease

Autonomic neuropathies are inherited or acquired neuropathies in which autonomic nerve fibers are selectively or disproportionately affected. Generally, sympathetic and parasympathetic fibers are both affected but there are exceptions. Acquired cases can be autoimmune; due to diabetes, amyloidosis, drugs, or toxins; or idiopathic. Autoimmune autonomic neuropathy is often subacute, sometimes associated with a neoplasm, and associated with high titers of antibody to ganglionic nicotinic acetylcholine receptor in about half of the severe cases. The molecular basis of inherited autonomic neuropathies is better known, including recent identification of the loci and genes of hereditary sensory and autonomic neuropathies types I, III, and IV. The inherited amyloid neuropathies are due to mutations of three proteins: transthyretin, apolipoprotein A1, and gelsolin. Non-invasive autonomic testing complements clinical and electrophysiological characterization of the autonomic neuropathies.

Neuromuscular pathology in hereditary gelsolin amyloidosis

Hereditary gelsolin amyloidosis (AGel amyloidosis) is a systemic disorder reported worldwide in kindreds with a G654A or G654T gelsolin gene mutation. The clinically characteristic peripheral nerve involvement has been poorly characterized morphologically, and its pathogenesis remains unknown. We studied peripheral nerve and skeletal muscle biopsy or autopsy specimens of 35 patients with a G654A gelsolin gene mutation. Histological, immunohistochemical, and electron microscopic studies showed consistent deposition of gelsolin amyloid (AGel), particularly in the vascular walls and perineurial sheaths. Nerve roots were more severely affected than distal nerves. The amyloid deposits also displayed variable immunoreactivity for apolipoprotein E, amyloid P component, cystatin C, and alpha-smooth muscle actin. Sural nerve morphometry showed preferential age-related large myelinated nerve fiber loss and reduction of myelin sheath cross-sectional area. There was evidence of denervation atrophy and fiber type grouping in skeletal muscle. Our study shows that marked proximal nerve involvement with AGel angiopathy is an essential feature of AGel amyloidosis. The preferential large fiber loss, not generally seen in amyloid neuropathy, may be caused by ischemia due to AGel angiopathy. Deficient actin modulation by variant gelsolin in neurons and Schwann cells, however, may alter axonal transport and myelination and contribute to AGel polyneuropathy.

Late onset lattice corneal dystrophy with systemic familial amyloidosis, amyloidosis V, in an English family

AIMS

To establish a clinical and molecular diagnosis in a family with late onset lattice corneal dystrophy.

METHODS

Linkage analysis, single strand conformation polymorphism (SSCP) analysis, and direct sequencing of genomic DNA were performed. A review of the patients' clinical symptoms and signs was undertaken.

RESULTS

Linkage to chromosome 9q34 was established and a mutation in the gelsolin gene was found in affected individuals. Numerous symptoms experienced by the patients were attributable to this mutation.

CONCLUSION

A diagnosis of amyloidosis type V (familial amyloidosis, Finnish type, FAF/Meretoja syndrome/gelsolin related amyloidosis) was made. This is the first case of amyloidosis type V described in the UK. This emphasises the importance of recognition of the extraocular manifestations of eye disease both in the diagnosis and management of the patient. In addition, these findings can help molecular geneticists in their search for disease-causing mutations.

Danish type gelsolin related amyloidosis: 654G-T mutation is associated with a disease pathogenetically and clinically similar to that caused by the 654G-A mutation (familial amyloidosis of the Finnish type)

BACKGROUND

Familial amyloidosis of the Finnish type (FAF, Finnish hereditary amyloidosis) is caused by a 654G-A mutation in the gelsolin gene on chromosome 9 resulting in the expression of mutant Asn-187 gelsolin which is abnormally proteolytically processed generating amyloidogenic fragments that polymerize into amyloid fibrils. We have recently shown that in a Danish and a Czech family with a clinical syndrome similar to FAF, including corneal lattice dystrophy, cranial neuropathy and skin changes, the disease is caused by another mutation at the same position, namely 654G-T predicting a Try-for-Asp substitution at 187 in secreted gelsolin.

AIM

To undertake a closer examination of the Danish subtype of FAF and report immunohistochemical and biochemical findings.

RESULTS

Immunostaining of plasma gelsolin isolated from heterozygous FAF of the Danish subtype revealed a pattern similar to that found in FAF-Asn 187. The > 60 kDa gelsolin species contain an epitope characteristic of the amyloid forming region as revealed by an amyloid specific antibody, whereas the approximately 50 kDa fragments are devoid of it. Compared with the wild-type gelsolin peptide (Asp-187), the corresponding mutant peptide (Tyr-187) showed dramatically increased fibrillogenicity as revealed by quantitative thioflavine-T based fluorimetry; ultrastructurally, amyloid-like fibrils were formed by the mutant peptide. Immunohistochemistry showed that antibodies directed against residues 231-242 of secreted gelsolin, representing the carboxy terminus of the sequence forming the amyloid protein (residues 173-243) laid down in the tissues in a fibrillar form in FAF, specifically labelled the amyloid deposited in rectum and skin in the Danish (654G-T) subtype.

CONCLUSIONS

The 654G-T mutation in the gelsolin gene gives rise to an amyloid disease clinically and pathogenetically similar to that caused by the 654G-A mutation.

Differing haemodynamic and catecholamine responses to exercise in three groups with peripheralautonomic dysfunction: insulin-dependent diabetes mellitus, familial amyloid polyneuropathy and pure autonomic failure

The haemodynamic and catecholamine responses to supine exercise, and the effect on standing blood pressure (BP), were studied in three groups with peripheral autonomic dysfunction; insulin-dependent diabetes mellitus (IDDM), familial amyloid polyneuropathy (FAP) and pure autonomic failure (PAF). Healthy normal subjects were studied as controls. With exercise, BP increased in controls, was unchanged in IDDM and FAP, and fell in PAF. Heart rate (HR) increased more in controls than IDDM, FAP or PAF. Cardiac index (CI) increased less in IDDM than controls, FAP or PAF. Systemic vascular resistance (SVR) fell similarly in controls and IDDM, with a greater fall in FAP and PAF. Plasma noradrenaline increased in controls and IDDM only; plasma adrenaline did not change and plasma dopamine was undetectable in all groups. On standing, BP was unchanged in controls; BP fell pre- and post-exercise in IDDM, FAP and PAF, with a significantly greater fall post-exercise in FAP and PAF. In conclusion, the haemodynamic responses to supine exercise and to standing after exercise differed in the three groups with peripheral autonomic dysfunction. These differences, and also the similarities, between different forms of peripheral autonomic dysfunction, may be of relevance to the clinical assessment and therapy of these patients.

Gelsolin-related familial amyloidosis, Finnish type (FAF), and its variants found worldwide

Gelsolin-related familial amyloidosis, Finnish type, occurs worldwide, most likely as a result of sporadic low-frequency mutations. Two mutations at nucleotide 654 in the gelsolin gene have been demonstrated, which result in a characteristic triad of ophthalmologic, neurologic and dermatologic manifestations distinct from other amyloidoses. Some phenotypic variation, particularly in the age of onset and severity of manifestations, occurs but in general the disease is clinically rather homogeneous. Systemic deposition of amyloid is found in most tissues, predominantly in blood vessel walls and associated with basement membranes. The mutations result in amino acid substitutions with a charge change in the gelsolin molecule, postulated to alter the susceptibility for proteases thereby rendering the molecule amyloidogenic. Gelsolin fragments constitute the amyloid fibrils, but abnormal fragments also occur in patients' plasma and CSF providing evidence for the role of aberrant proteolysis in the disease pathomechanism. This is further strengthened by in vitro expression analyses showing both disease-related mutations to result in secretion of an abnormal gelsolin fragment, the likely precursor protein of gelsolin amyloid. Of the two forms of gelsolin, secretory and cytoplasmic, the secretory plasma form is the likely source of amyloid. The origin of the systemic amyloid deposits is not known but, beside a circulatory origin, local synthesis and deposition is an attractive pathomechanical alternative. The final goal of preventing or curing this disease has come closer, but still awaits further comprehensive pathological, functional and experimental studies in order to dissect all pathogenetically important events.

Peripheral nerve amyloidosis

Peripheral nerve amyloidosis is the cardinal feature of familial amyloid polyneuropathy (FAP) but can also be seen in primary light chain (AL) amyloidosis and dialysis (beta 2-microglobulin) related amyloidosis. The generalized neuropathy seen in all forms of peripheral nerve amyloidosis is similar, characterized by a severe progressive mixed neuropathy with autonomic dysfunction. Pathologically, amyloid is found in the peripheral nervous system as amorphous, eosinophilic, extracellular deposits. FAP is most commonly associated with variant plasma transthyretin (TTR), although it has also been described in association with mutant apolipoprotein A-1 and gelsolin. There are now at least 36 point mutations in the TTR gene associated with FAP and these continue to be described. Recent studies on the possible role individual point mutations in the TTR gene may play in amyloidosis have helped give us an insight into the mechanisms behind peripheral nerve amyloidosis. This article reviews the clinical and pathological features of the peripheral nerve amyloidosis and discusses theories of amyloidogenesis based on studies of FAP.