Cutis laxa in hereditary gelsolin amyloidosis

Exploring clinical variability in gelsolin amyloidosis: Brazilian family case study with confocal microscopy

INTRODUCTION

Genetic mutations or inflammatory, degenerative, or neoplastic conditions can trigger amyloidosis. Hereditary gelsolin amyloidosis is a genetic disorder primarily marked by amyloid fibrils composed of misfolded gelsolin fragments.

CASE REPORT

We present three sisters with AGel amyloidosis, illustrating its clinical diversity. Patient 1, a 51-year-old, had bilateral ptosis, ocular discomfort, and dry eye syndrome due to cranial nerve involvement. Patient 2, a 53-year-old, experienced progressive bilateral visual impairment. Patient 3, a 50-year-old, exhibited right eye ectropion. Genetic analysis, with the identical mutation, heterozygous c.640G > A (p.Asp214Asn) mutation, confirmed AGel amyloidosis diagnoses, with common findings including lattice corneal amyloidosis, reduced corneal sensitivity, and recurrent corneal erosions. Neurological manifestations included ataxia and peripheral neuropathy, with skin abnormalities observed in patient 1. Ocular involvement severity and distribution varied among patients.

DISCUSSION

Common ocular and neurological manifestations validated AGel amyloidosis diagnoses, reinforcing its hereditary basis. Neurological symptoms highlighted the disorder's impact on various organ systems, while skin abnormalities contributed to ocular discomfort. Variable ocular involvement emphasized the disorder's heterogeneity. These patients emphasize hereditary gelsolin amyloidosis's clinical diversity and suggest potential environmental influences on disease expression. Genetic confirmation and confocal microscopy findings reaffirm the genetic basis while raising questions about assessing systemic disease severity, necessitating further investigation in larger cohorts. Ophthalmologists' specialized care is crucial for managing ocular symptoms, given the absence of a universal cure.

A novel hotspot of gelsolin instability triggers an alternative mechanism of amyloid aggregation

Gelsolin comprises six homologous domains, named G1 to G6. Single point substitutions in this protein are responsible for AGel amyloidosis, a hereditary disease causing progressive corneal lattice dystrophy, cutis laxa, and polyneuropathy. Although several different amyloidogenic variants of gelsolin have been identified, only the most common mutants present in the G2 domain have been thoroughly characterized, leading to clarification of the functional mechanism. The molecular events underlying the pathological aggregation of 3 recently identified mutations, namely A551P, E553K and M517R, all localized at the interface between G4 and G5, are here explored for the first time. Structural studies point to destabilization of the interface between G4 and G5 due to three structural determinants: β-strand breaking, steric hindrance and/or charge repulsion, all implying impairment of interdomain contacts. Such rearrangements decrease the temperature and pressure stability of gelsolin but do not alter its susceptibility to furin cleavage, the first event in the canonical aggregation pathway. These variants also have a greater tendency to aggregate in the unproteolysed forms and exhibit higher proteotoxicity in a C. elegans-based assay. Our data suggest that aggregation of G4G5 variants follows an alternative, likely proteolysis-independent, pathway.

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.

Acral localized acquired cutis laxa as presenting sign of underlying systemic amyloidosis

Acral localized acquired cutis laxa (ALACL) is a rare variant of acquired cutis laxa, and the clinical appearance is characterized by loose, redundant and wrinkled skin of the distal extremities. By definition, histopathology of affected tissue reveals sparse or fragmented elastic fibers. However, this can be difficult to assess on routine staining, and sometimes requires electron microscopy. The condition has been associated with plasma cell dyscrasias or recurrent inflammatory states. We present a case of a 65-year-old man who presented with enlarged and doughy finger pads. Skin biopsy showed diffuse dermal amyloid deposition displacing dermal stroma and reduction of elastic fibers, although these changes were subtle on routine hematoxylin and eosin staining. Mass spectrometry of laser capture microdissected tissue showed AL kappa-type amyloid and further workup revealed a diagnosis of primary systemic AL-kappa amyloidosis requiring bone marrow transplantation. This case represents an unusual presentation of acquired cutis laxa and highlights the need for a high index of suspicion when reviewing histopathology of this entity. In addition, the case highlights the importance of investigation into possible systemic associations, such as plasma cell dyscrasias.

Review of proteomics approach to eye diseases affecting the anterior segment

Visual impairment and blindness is a major health burden worldwide, and major ocular diseases causing visual impairment pertain to the anterior segment of the eye. Anterior segment ocular diseases are common, yet complex entities. Although many treatment options and surgical techniques are available for these ailments, the underlying cause and pathogenesis is still unclear. Finding ways to fundamentally treat these patients and rectify the underlying dysregulations leading to the disease may help cure patients completely without major complications. Proteomics approaches are a novel way to distinguish dysregulated proteins in a variety of biological tissues in a hypothesis-free manner, thus helping to find the responsible pathways leading to a certain disease. The aim of the current study is to review the available knowledge in scientific literature regarding the proteomics studies done on anterior segment eye diseases and suggest potential clinical implications to exploit the results of these studies. SIGNIFICANCE: Anterior segment ocular diseases are responsible for a major proportion of visual impairment and blindness worldwide. Although ophthalmologists have several treatment options that can alleviate or control the progression of these diseases, no definite cure is available for most of them. Moreover, because these diseases are progressive, prompt diagnosis is of utmost important. Proteomics studies enable us to identify and quantify the dysregulated proteins in a biological specimen in a hypothesis-free manner. Understanding the dysregulated protein pathways shines a light on the pathogenesis of the disease. Moreover, these dysregulated proteins may act as biomarkers to help in diagnosis and treatment follow-up. Hence, in this article we sought out to review the available scientific literature regarding the proteomics studies of anterior segment ocular diseases and to identify potential applications of proteomic studies in clinic.

Severe elastolysis in hereditary gelsolin (AGel) amyloidosis

AGel amyloidosis is a dominantly inherited systemic amyloidosis caused by mutations p.D214N or p.D214Y resulting in gelsolin amyloid (AGel) formation. AGel accumulates extracellularly in many tissues and alongside elastic fibres. AGel deposition associates with elastic fibre degradation leading to severe clinical manifestations, such as cutis laxa and angiopathic complications. We analysed elastic fibre pathology in dermal and vascular tissue and plasma samples from 35 patients with AGel amyloidosis and 40 control subjects by transmission electron microscopy, immunohistochemistry and ELISA methods. To clarify the pathomechanism(s) of AGel-related elastolysis, we studied the roles of MMP-2, -7, -9, -12 and -14, TIMP-1 and TGFβ. We found massive accumulation of amyloid fibrils along elastic fibres as well as fragmentation and loss of elastic fibres in all dermal and vascular samples of AGel patients. Fibrils of distinct types formed fibrous matrix. The degradation pattern of elastic fibres in AGel patients was different from the age-related degradation in controls. The elastin of elastic fibres in AGel patients was strongly decreased compared to controls. MMP-9 was expressed at lower and TGFβ at higher levels in AGel patients than in controls. The accumulation of amyloid fibrils with severe elastolysis characterises both dermal and vascular derangement in AGel amyloidosis.

[Multifocal chalazodermic amyloidosis: The concept of immunoglobulinemic elastopathy]

INTRODUCTION

Impairment of dermal elastic tissue occurs in different entities associated with immunoglobulins or immunoglobulin-derived protein-secreting clonal plasma cell proliferations, such as amyloid elastosis, anetodermic nodular amyloidosis or monoclonal gammopathy-associated cutis laxa. We report a case of cutaneous immunoglobulinemic amyloidosis revealed by a unique chalazodermic presentation and we review elastic tissue impairment in patients with monoclonal gammopathies.

OBSERVATION

A 67-year-old woman consulted for non-infiltrated anetodermic lesions on the upper left quadrant of her abdomen present for ten years. She also had a chalazodermic plaque with abnormal skin wrinkling and laxity in her right axilla. Biopsies revealed deep dermal and subcutaneous amyloid deposits. Immunohistochemistry with lambda light chain was positive. Orcein staining and electron microscopy showed extensive elastolysis. The patient presented no signs of systemic involvement, but a very small amount of monoclonal IgGλ gammopathy was detected during follow-up.

DISCUSSION

This is a unique chalazodermic presentation of immunoglobulinemic amyloidosis that does not fit into a clearly-defined nosological setting. It highlights the complex interactions between immunoglobulin-derived proteins, including light and heavy chains, and elastic tissue components, leading to different types of impairment of the latter. We therefore suggest the unifying concept of immunoglobulinemic elastopathy, underscoring the need to screen for monoclonal gammopathy in patients presenting elastic tissue impairments.

Clinical, biopsy, and mass spectrometry findings of renal gelsolin amyloidosis

Gelsolin amyloidosis is a rare type of amyloidosis typically involving the cranial and peripheral nerves, but rarely the kidney. Here we report the clinical, kidney biopsy, and mass spectrometry findings in 12 cases of renal gelsolin amyloidosis. Of the 12 patients, five were men and seven were women with mean age at diagnosis of 63.8 years. Gelsolin amyloidosis was most common in Caucasians (six patients) and Asians (four patients), and included one each African-American and Hispanic patients. Nephrotic syndrome was the most common cause of biopsy, although most patients also had progressive loss of kidney function. Hematological and serological evaluation was negative in 11 patients, while one patient had a monoclonal gammopathy. The renal biopsy showed large amounts of pale eosinophilic Congo red-positive amyloid deposits typically restricted to the glomeruli. Immunofluorescence studies were negative for immunoglobulins in nine cases with three cases of smudgy glomerular staining for IgG. Electron microscopy showed mostly random arrangement of amyloid fibrils with focally parallel bundles/sheets of amyloid fibrils present. Laser microdissection of the amyloid deposits followed by mass spectrometry showed large spectra numbers for gelsolin, serum amyloid P component, and apolipoproteins E and AIV. Furthermore, the p. Asn211Lys gelsolin mutation on mass spectrometry studies was detected in three patients by mass spectrometry, which appears to represent a renal-limited form of gelsolin amyloidosis. Thus, renal gelsolin amyloidosis is seen in older patients, presents with nephrotic syndrome and progressive chronic kidney disease, and histologically exhibits glomerular involvement. The diagnosis can be confirmed by mass spectrometry studies.

Increasing amount of amyloid are associated with the severity of clinical features in hereditary gelsolin (AGel) amyloidosis

BACKGROUND

Patients with hereditary gelsolin (AGel) amyloidosis (HGA) present with hanging skin (cutis laxa) and bilateral cranial neuropathy, and require symptomatic plastic surgery. Our clinical observation of tissue fragility prompted us to design a prospective study.

METHODS

Twenty-nine patients with HGA undergoing surgery were interviewed and clinically examined. The height and thickness of skin folds in standard anatomical localizations were measured. The presence and distribution of amyloid in skin samples were analyzed using Congo red staining and immunohistochemistry using antibodies against gelsolin amyloid (AGel) subunit.

RESULTS

The measured skin folds stretched more in patients with HGA (e.g. skin over olecranon, p < 0.001). The skin folds were thinner in patients with HGA (e.g. forehead skin, p < 0.001). The skin and subcutaneous fat were abnormally fragile during surgery. The total amount of AGel amyloid, and its presence in the deep layers of the skin and subcutaneous fat correlated with the measurements of skin folds, age and extent of cranial neuropathy.

CONCLUSIONS

The AGel amyloid in the skin and subcutis, together with morphologic changes in the dermal stroma and skin adnexa contribute to the atrophied and fragile structure of HGA skin. This is the first study to demonstrate the correlation between AGel amyloid accumulation and clinical disease severity.

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.

Familial Amyloid Polyneuropathy Type IV (FINNISH) with Rapid Clinical Progression in an Iranian Woman: A Case Report

Familial amyloid polyneuropathy (FAP) type IV (FINNISH) is a rare clinical entity with challenging neuropathy and cosmetic deficits. Amyloidosis can affect peripheral sensory, motor, or autonomic nerves. Nerve lesions are induced by deposits of amyloid fibrils and treatment approaches for neuropathy are challenging. Involvement of cranial nerves and atrophy in facial muscles is a real concern in daily life of such patients. Currently, diagnosis of neuropathy can be made by electrodiagnostic studies and diagnosis of amyloidosis can be made by genetic testing or by detection of amyloid deposition in abdominal fat pad, rectal, or nerve biopsies. It is preferable to consider FAP as one of the differential diagnosis of a case presented with multiple cranial nerves symptoms. The authors present a case of familial amyloid polyneuropathy (FAP) type IV with severe involvement of multiple cranial nerves, peripheral limb neuropathy, and orthostatic hypotension.

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.

Gender differences in the clinical course of Finnish gelsolin amyloidosis

PURPOSE

To investigate gender differences in Finnish gelsolin amyloidosis (AGel amyloidosis).

PATIENTS AND METHODS

AGel amyloidosis patients, who were members of Finnish Amyloidosis Association (SAMY), filled in a questionnaire compiling known and suspected aspects of their disease. Telephone interviews and hospital medical records, when available, complemented the questionnaire. The data were entered to the database in order to create a national AGel amyloidosis patient registry (FIN-GAR).

RESULTS

A total of 227 patients, 156 women and 71 men, participated in the study. The women in our registry noticed their first symptoms at the median age of 39 years versus 43 years for men (p = 0.01). At the age in which the diagnosis was made there was a trend to be observed between men and women (women: 39 years versus men: 43 years, p = 0.053). Corneal lattice dystrophy was diagnosed in significantly younger women than men (median ages 41 versus 49 years, respectively, p = 0.01). Of other ophthalmological manifestations, corneal ulcer, impaired vision and glaucoma were all diagnosed at least 5 years earlier in women, although differences were not statistically significant. Ophthalmological manifestations, such as dry eyes and corneal ulcer; dermatological signs, such as blepharochalasis, and also neurological symptoms, such as myokymia and carpal tunnel syndrome, were more prevalent among women.

CONCLUSIONS

In the largest so far available study on AGel amyloidosis we show that women developed symptoms and signs of AGel amyloidosis at younger age. Especially eye-related problems occurred earlier and together with nerve and skin manifestations, the characteristic clinical triad in AGel amyloidosis, were more common in women. However, a clear limitation of our study was a selection bias caused by a significant underrepresentation of men in the study population.

Natural course of Finnish gelsolin amyloidosis

BACKGROUND

Finnish type of hereditary gelsolin amyloidosis (FGA) is one of the most common diseases of Finnish disease heritage. Existing FGA knowledge is based only on smaller patient series, so our aim was to elucidate the natural course of the disease in a comprehensive sample of patients and to build up a national FGA patient registry.

METHODS

An inquiry about the known and suspected signs of FGA, sent to the members of Finnish Amyloidosis Association, telephone contacts, and hospital records were utilized to create the registry.

RESULTS

A total of 227 patients were entered to the database. The first symptom was ophthalmological for 167 patients (73.6%) at the mean age of 39 years. Corneal lattice dystrophy (CLD) was reported at the mean age of 43 years. Impaired vision, polyneuropathy, facial nerve paresis, and cutis laxa appeared on average between 52 and 57 years. Carpal tunnel syndrome (CTS) was reported by 86 patients (37.9%). Nine patients (4.0%) had a pacemaker, and 12 (6.1%) had cardiomyopathy.

CONCLUSIONS

The first symptom was ophthalmological in most cases. Except for CLD no prominent difference in the age of appearance was found between the major symptoms. CTS, cardiac pacemakers, and cardiomyopathy were remarkably more common compared to the general population.

Xerostomia in hereditary gelsolin amyloidosis

Hereditary gelsolin amyloidosis (AGel amyloidosis) is a rare, dominantly inherited systemic disease with worldwide distribution, caused by c.654G > A or c.654G > T gelsolin gene mutation. The disease mainly manifests with late-onset dystrophy of the cornea, laxity of the skin and dysfunction of the cranial nerves whereas the oral manifestations have remained less-studied. To examine if AGel amyloidosis also affects salivary gland function, we studied 27 patients. In a questionnaire, 89% of them reported oral dryness, and 74% oral and ocular dryness. Unstimulated (UWS) and stimulated whole salivary flow (SWS) rates were measured, and salivary proteins were analyzed in the patients and controls. Hyposalivation according to UWS was detected in 67% of the patients, while decreased SWS occurred in 63% of the patients and 19% of the controls (p = 0.001). The secretion rates of salivary total protein and IgA were significantly lower in patients than controls. Histopathological analyses of labial salivary gland biopsies showed deposition of gelsolin amyloid, atrophy and inflammation. This study showed that AGel amyloidosis belongs to the differential diagnostic choices to be kept in mind in the patients presenting with xerostomia, low secretion rates of salivary total protein and IgA and/or deposition of amyloid in the minor salivary glands. AGel amyloidosis patients should be advised for efficient dental care.

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.

Cutaneous amyloidosis: a concept review

Concepts and semantics are crucial for good communication between clinicians and pathologists. Amyloidosis was described more than 150 years ago. Therefore, the terminology related to it is abundant, varied, and sometimes complex. In this report, we intend to discuss several terms related to the disease, with special emphasis on cutaneous amyloidosis. We present a review, from Virchow to present, of the concepts related to amyloidosis: its nature, the classification of cutaneous forms of the disease, and the techniques used in its diagnosis.

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.

Familial amyloid polyneuropathy

Familial amyloid polyneuropathies (FAPs) are a group of life-threatening multisystem disorders transmitted as an autosomal dominant trait. Nerve lesions are induced by deposits of amyloid fibrils, most commonly due to mutated transthyretin (TTR). Less often the precursor of amyloidosis is mutant apolipoprotein A-1 or gelsolin. The first identified cause of FAP-the TTR Val30Met mutation-is still the most common of more than 100 amyloidogenic point mutations identified worldwide. The penetrance and age at onset of FAP among people carrying the same mutation vary between countries. The symptomatology and clinical course of FAP can be highly variable. TTR FAP typically causes a nerve length-dependent polyneuropathy that starts in the feet with loss of temperature and pain sensations, along with life-threatening autonomic dysfunction leading to cachexia and death within 10 years on average. TTR is synthesised mainly in the liver, and liver transplantation seems to have a favourable effect on the course of neuropathy, but not on cardiac or eye lesions. Oral administration of tafamidis meglumine, which prevents misfolding and deposition of mutated TTR, is under evaluation in patients with TTR FAP. In future, patients with FAP might benefit from gene therapy; however, genetic counselling is recommended for the prevention of all types of FAP.

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.

[Cutaneous amyloidosis]

Amyloids are common protein aggregates in nature. Some amyloids fulfill important biological tasks while others are known to cause diseases. Despite the fact that the ultrastructure of amyloid is highly conserved, the mechanism of amyloidogenesis remains a challenging research topic. In humans, amyloidoses may develop in the skin or lead to skin signs due to secondary cutaneous involvement. An accurate diagnostic procedure is crucial for planning the therapy of this heterogeneous group of diseases. Therefore, the aim of this paper is to give an overview on the different kinds of amyloidoses as well as on diagnostic and therapeutic approaches. Furthermore, the discrimination between functional and disease-causing amyloid is briefly presented.

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 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.

Lattice corneal dystrophy, gelsolin type (Meretoja's syndrome)

PURPOSE

This paper reviews current knowledge about the pathogenesis, clinical manifestations and treatment of lattice corneal dystrophy, gelsolin type (LCD2, Meretoja's syndrome).

METHODS

Material is derived from literature searches, a case study of a Finnish patient living in Sweden, and interviews in Helsinki with Professor Ahti Tarkkanen and Dr Sari Kiuru-Enari, both of whom have extensive first-hand experience in treating patients with the disease.

RESULTS

The disease is now reported from several countries in Europe, as well as Japan, the USA and Iran. Treatment is symptomatic and is based on eye lubrication combined with rigorous monitoring of intraocular pressure to reduce corneal haze and postpone the need for keratoplasty. When systemic symptoms occur, the ophthalmologist should consult other specialists.

CONCLUSIONS

The disease is probably under-reported and is almost certainly to be found in more countries, including Sweden. Every ophthalmologist should be vigilant and consider this diagnosis when discovering a corneal lattice dystrophy, especially because the disease is an inherited, lifelong chronic condition with systemic symptoms.

[Hereditary and non-hereditary cutaneous amyloidoses]

Amyloid and amyloidosis describes a heterogeneous group of diseases which are characterized by the pathological extracellular deposition of autologous proteins. Basically, amyloidoses can be divided into systemic or organ-limited (e.g. cutaneous) forms and can be acquired or hereditary in nature. The subclassification discriminates between primary amyloidosis (in the absence of an obvious predisposing disease) and secondary amyloidosis (if caused by a certain underlying disease). The subclassification of amyloidoses is based on the main protein constituent and therefore on the chemical composition of the amyloid fibrils. However, the exact etiopathogenesis of amyloid formation remains unclear. In addition to the clinical presentation, histology, electron microscopy and biochemical-immunological differentiation are also decisive for a proper diagnosis. In cutaneous amyloidosis the deposition of amyloid either occurs along reticulin fibers and the basal membrane (perireticulary amyloidoses) or along collagen fibers (pericollagenous amyloidosis). The purpose of this article is to provide an up-to-date overview on the different kinds of cutaneous amyloidoses.

Generalized cutis laxa and fibrillar glomerulopathy resulting from IgG Deposition in IgG-lambda Monoclonal Gammopathy: pulmonary hemorrhage during stem cell mobilization and complete hematological response with bortezomib and dexamethasone therapy

The case of a 52-years-old man with generalized acquired cutis laxa associated with IgG-lambda monoclonal gammopathy and nephrotic syndrome with renal failure (due to fibrillar glomerulopathy resulting from IgG deposition) is reported. A peripheral blood autologous stem cell transplant was planned, but the procedure was complicated by severe pulmonary hemorrhage during stem cells mobilization with granulocyte colony-stimulating factor (G-CSF). Treatment with bortezomib and dexamethasome was subsequently started and a complete hematological response was achieved. Finally, the complete hematological response with the disappearance of the toxic M-protein allows the possibility of a long-term benefit with a kidney transplant followed by an autologous bone marrow transplant.

Amyloidogenesis of natively unfolded proteins

Aggregation and subsequent development of protein deposition diseases originate from conformational changes in corresponding amyloidogenic proteins. The accumulated data support the model where protein fibrillogenesis proceeds via the formation of a relatively unfolded amyloidogenic conformation, which shares many structural properties with the pre-molten globule state, a partially folded intermediate first found during the equilibrium and kinetic (un)folding studies of several globular proteins and later described as one of the structural forms of natively unfolded proteins. The flexibility of this structural form is essential for the conformational rearrangements driving the formation of the core cross-beta structure of the amyloid fibril. Obviously, molecular mechanisms describing amyloidogenesis of ordered and natively unfolded proteins are different. For ordered protein to fibrillate, its unique and rigid structure has to be destabilized and partially unfolded. On the other hand, fibrillogenesis of a natively unfolded protein involves the formation of partially folded conformation; i.e., partial folding rather than unfolding. In this review recent findings are surveyed to illustrate some unique features of the natively unfolded proteins amyloidogenesis.

Elastic fibers and amyloid deposition in vascular tissue

Amyloid fibrils are associated with a large number of diseases, such as Alzheimer’s dementia and others. Evidence links Alzheimer’s dementia with vascular diseases and only few data connect amyloids and atherosclerosis and aging via deposits in the aortic intima. Recent results demonstrate that some elastin polypeptide sequences are also able to produce amyloid fibers. This finding could have useful implications in the study of amyloids in cardiovascular tissue whose main constituent is elastin. In this review, we have also outlined the main characterizing features regarding the structure of amyloid fibrils. Finally, we describe, as a future perspective, the design of proper inhibitors of amyloid deposition in vascular walls as potential therapeutic drugs.

Severe ataxia with neuropathy in hereditary gelsolin amyloidosis: a case report

Hereditary gelsolin amyloidosis (AGel amyloidosis) is a systemic disorder caused by a G654A or G654T gelsolin mutation, reported from Europe, North America, and Japan. Principal clinical signs are corneal lattice dystrophy, cutis laxa and cranial neuropathy, often deleterious at advanced age. Peripheral neuropathy, if present, is usually mild. We report a 78-year-old male Finnish patient who presented with ataxia and mainly sensory peripheral polyneuropathy (PNP) signs, causing severe disability and ambulation loss. Electrophysiological studies showed severe generalized chronic mainly axonal sensorimotor PNP with facial paralysis. In magnetic resonance imaging proximal lower limb and axial muscle atrophy with fatty degeneration as well as moderate spinal cord atrophy were seen. A G654A gelsolin mutation was demonstrated but no other possible causes of his disability were found. At age 79 years he became bedridden and died of pulmonary embolism. Neuropathological examination revealed marked gelsolin amyloid deposition at vascular and connective tissue sites along the entire length of the peripheral nerves extending to the spinal nerve roots, associated with severe degeneration of nerve fibers and posterior columns. Our report shows that advanced AGel amyloidosis due to degeneration of central and distal sensory nerve projections results in deleterious ataxia with fatal outcome. Severe posterior column atrophy may reflect radicular AGel deposition, although even altered gelsolin-actin interactions in neural cells possibly contribute to neurodegeneration with successive ataxia in carriers of a G654A gelsolin mutation.

Heparin accelerates gelsolin amyloidogenesis

The chemical environment of the extracellular matrix may influence the tissue-selective deposition observed there in gelsolin amyloid disease. Previously, we have identified the proteases that generate the amyloidogenic fragments from the full-length gelsolin variants and demonstrated that heparin is capable of accelerating gelsolin amyloidogenesis. Herein, we identify the structural features of heparin that promote the 8 kDa disease-associated gelsolin fragments (residues 173-243) generated at the cell surface to form amyloid. In conjunction with electron microscopy analyses, our kinetic studies demonstrate that heparin efficiently accelerates the formation of gelsolin amyloid by enabling intermolecular beta-sheet formation. The use of heparin analogues reveals that sulfation is important in accelerating amyloidogenesis and that the extent of acceleration is proportional to the molecular weight of heparin. In addition, heparin accelerated aggregation at both early and late stages of amyloidogenesis. Dynamic light scattering coupled to size exclusion chromatography showed that heparin promotes the formation of soluble aggregates. Collectively, these data reveal that heparin templates fibril formation and affords solubility to the aggregating peptides through its sulfated structure. By extension, the biochemical results herein suggest that tissue-selective deposition characteristic of the gelsolin amyloidoses is likely influenced by the extracellular localization of distinct glycosaminoglycans.