Protein AA and lattice corneal dystrophy

Ocular amyloidosis, with special reference to the hereditary forms with vitreous involvement

The complex of diseases referred to as amyloidosis is characterized by the deposition of amyloid substance in various tissues. The amyloid protein differs in the various forms of amyloidosis. This variation is the basis of the differences in affected tissues and subsequent clinical dissimilarities. Vitreous involvement in amyloidosis seems to be especially linked to some of the hereditary neuropathies associated with the amyloid protein transthyretin. Characterization of the amyloid proteins during recent decades has allowed a chemical and immunologic classification of amyloid fibrils. This paper presents the basis for classification of amyloidosis, reviews the literature on ocular amyloidosis, with special reference to vitreous involvement, and summarizes clinical findings and frequency of vitreous amyloid involvement in Swedish patients with familial amyloidotic polyneuropathy.

Immunohistochemical analysis of lattice corneal dystrophies types I and II

Corneal buttons from four patients with lattice corneal dystrophy (LD) type I, thought to be an isolated corneal amyloidosis, and from six patients with LD type II, part of systemic familial amyloidosis, Finnish type (FAF; Meretoja's syndrome), were studied by immunohistochemistry to determine the differential distribution in the amyloid deposits of amyloid P component (AP), mutated gelsolin specific for FAF, and native gelsolin. In both types of LD, antibodies to AP labelled lattice lines and a discontinuous layer of amyloid deposits under Bowman's layer. In LD type II, particularly, they also reacted with streak-like amyloid deposits between corneal almellae, especially in the limbal region. While the anti-FAF antiserum strongly labelled all amyloid deposits in LD type II, it failed to react unequivocally with them in LD type I. Both in LD type I and in two control specimens representing granular dystrophy, the monoclonal antibody (MAb) GS-2C4 to gelsolin faintly labelled some deposits, while in LD type II it reacted non-homogeneously with most amyloid deposits. In all specimens, MAb GS-2C4 labelled corneal epithelial cells and occasional stromal keratocytes and endothelial cells. The results suggest that Meretoja's syndrome, a systemic disease, can be diagnosed even retrospectively from corneal buttons subjected to histopathological study.

Secondary localized amyloidosis in interstitial keratitis. Clinicopathologic findings

Cases of secondary localized corneal amyloidosis have been described in various corneal and ocular inflammations but are believed to occur uncommonly. The authors examined histopathologic specimens from 33 consecutive patients with interstitial keratitis who underwent penetrating keratoplasty for visual rehabilitation. In 11 cases (33%), multiple fusiform deposits of amyloid were identified and confirmed in middle and deep corneal stroma using histochemical staining. Characteristic electron microscopic findings were present in two cases. These results indicate that secondary localized corneal amyloidosis occurs frequently in interstitial keratitis and displays a distinct pattern of deposition.

Primary localized amyloidosis of the lacrimal glands

Primary localized amyloidosis causing bilateral lacrimal enlargement is rare. The pathogenesis of amyloid deposition within the orbit and other body tissues has not been fully elucidated. The authors report the case of a 72-year-old woman who presented with bilateral lacrimal gland enlargement secondary to amyloid infiltration. The chemical nature of the deposit was characterized using light microscopy, immunohistochemistry, and immunoelectron microscopy. The primary (immunocytic) nature of the amyloid was confirmed by immunohistochemistry demonstrating the presence of monoclonal lambda light chains in the amyloid deposits and in the plasma cells. Using immunoelectron microscopy, amyloid deposits were seen containing lambda light chains in macrophages. It has been postulated that the macrophage has a role in amyloid deposition. The authors believe this to be the first published report of immunoelectron microscopy use in orbital amyloidosis, and that this technique has helped further their understanding of the nature and pathogenesis of this condition.

Clinical and histopathologic studies of two families with lattice corneal dystrophy and familial systemic amyloidosis (Meretoja syndrome)

Lattice corneal dystrophy associated with familial systemic amyloidosis (Meretoja syndrome) has rarely been described other than in patients of Finnish origin. The authors report two North American patients with this disease who manifest blepharochalasis, lattice corneal dystrophy, open-angle glaucoma, and cranial neuropathy. In one patient, a corneal intraepithelial and subepithelial pseudodendrite was managed by superficial keratectomy, and this same patient benefited from surgical brow suspension for facial muscular weakness. In the second patient, penetrating keratoplasty was complicated by a neurotrophic persistent epithelial defect. Corneal tissue from both superficial keratectomy and penetrating keratoplasty exhibited ultrastructurally characteristic amyloid filaments and associated elastoid material. Transmission electron microscopy of conjunctiva and skin biopsies similarly revealed amyloid deposits associated with most basement membranes, the perineurium and endoneurium of most peripheral nerves, and the intima and media of arteries. By immunoperoxidase staining, the corneal amyloid deposits were positive for the amyloid P-component protein but negative for the nonimmunoglobulin amyloid A protein and prealbumin. Serum prealbumin and amyloid A related protein were normal.

Amyloidosis of corneal stroma in patients with trachoma. A clinicopathologic study of 62 cases

Sixty-two cases of corneal amyloidosis were studied. The median age of the 48 men and 14 women was 66 years. The patients had bilateral, diffuse corneal opacity extending to the limbus and severe visual impairment. The corneal condition was not familial. Advanced stages of trachoma were present in all individuals. Climatic droplet keratopathy (CDK) was also observed clinically in 19 patients. Histopathologically, the Congo red-positive, birefringent and dichroic amyloid deposits in the stroma were similar to that of lattice corneal dystrophy. Bowman's membrane was mostly absent, and peculiar microcystoid degeneration of the stroma was noted. Electron microscopic studies not only confirmed the diagnosis of amyloid but also showed a more diffuse amyloid pattern than did light microscopy. Trachoma is probably the cause of this corneal degeneration with secondary amyloidosis. The environmental conditions associated with CDK may be contributing factors in some cases.

Corneal elastosis within lattice dystrophy lesions

Corneal buttons of two patients with lattice corneal dystrophy were studied by light and electron microscopy. They showed elastotic degeneration within the amyloid deposits. The amyloid deposits displayed characteristic staining; the elastotic material (elastin) within the deposits stained positive with Verhoeff-van Gieson and Movat pentachrome stains and showed autofluorescence. The characteristic ultrastructural findings of amyloid and elastotic material were also demonstrated. The possibility of the associations of these two materials in the cornea is discussed.

Corneal amyloidosis associated with keratoconus

Nodular, gray-white, central corneal opacities which extended from the subepithelial zone through the anterior four fifths of the stroma developed in a 50-year-old man with a longstanding history of hard contact lens wear for keratoconus. Results of histopathologic analysis of the corneal button obtained at the time of penetrating keratoplasty disclosed that the opacities were composed of amyloid. Corneal amyloidosis is rarely found in association with keratoconus. Although there were some similarities in the pattern of amyloid deposition to that seen in primary familial amyloidosis of the cornea, the authors believe that their patient is more likely to have had a secondary amyloidosis. Corneal amyloidosis should be considered in keratoconus patients with development of unusual forms of central corneal opacification.

Scleromyxedema with corneal deposits

Scleromyxedema (Arndt-Gottron syndrome) is a rare cutaneous disease in which hyaluronic acid is deposited in the dermis. The authors describe a patient with scleromyxedema and corneal deposits. A corneal biopsy demonstrated hyaluronic acid deposition in the corneal stroma and amyloid P component in Bowman's membrane. This is the first report of scleromyxedema involving the cornea. It is also the first report of amyloid P component deposition in the cornea occurring independent of corneal amyloid deposits.

Histopathologic and immunochemical features of lattice corneal dystrophy type III

We examined seven corneas from five patients with a new form of lattice corneal dystrophy (designated lattice corneal dystrophy type III) by light and electron microscopy. Numerous amyloid deposits were scattered throughout the corneal stroma, some of which were much larger than those usually observed in either lattice corneal dystrophy type I or II; these were located predominantly midway between the epithelium and the endothelium. Image analysis disclosed that the cross-sectional size of the large stromal amyloid deposits was significantly greater than those in age-matched patients with lattice corneal dystrophy type I. All patients had a discontinuous band of amyloid (15 to 25 micron wide) in the superficial stroma beneath Bowman's layer, which usually had only one or two small disruptions. Descemet's membrane and the endothelium were normal. The stromal deposits, which were composed of 10-nm diameter fibrils typical of amyloid, stained positively with Congo red after the histologic sections were pretreated with dilute potassium permanganate. Immunohistochemical studies on formalin-fixed, paraffin-embedded tissue indicated that only some deposits reacted weakly with antibodies to amyloid protein AA. The deposits stained positively with antibodies to protein AP and negatively with antibodies to kappa and lambda immunoglobulin light chains.

Localized conjunctival amyloidosis associated with extranodal lymphoma

A 62-year-old man was found to have a large asymptomatic amyloid nodule of the conjunctiva. Within the next year, a diffuse mixed small and large cell lymphoma of his scapula developed with amyloid in its stroma. No abnormal serum or urine protein was found. Subsequently, rib and paraspinal masses appeared. After irradiation and chemotherapy, the patient died of bronchopneumonia, 3 years after onset. By immunostaining, the amyloid of both conjunctiva and scapular tumor was of polyclonal immunoglobulin (AL) type, most prominently IgG and lambda chains, with lesser staining for IgA and kappa chains. The tumor cells showed a similar pattern. To our knowledge, this is the first report of systemic lymphoma and localized conjunctival amyloidosis without a serum paraprotein, and the first such association with a lymphoma of this cell type. Immunotyping of conjunctival amyloidosis should be performed to guide the workup for possible systemic disease.

Immunoglobulin deposition in localized conjunctival amyloidosis

Immunofluorescent studies were performed on tarsus and tarsal conjunctiva from a 30-year-old woman with blepharoptosis secondary to localized nonfamilial amyloidosis. Both kappa and lambda light chains were identified in abundance in the resected tissue. There was no evidence of any systemic disease or of amyloid deposition elsewhere. Six months after the patient underwent surgery, there was no sign of recurrence. The antigenic determinants of the amyloid suggested that the pathogenesis of localized nonfamilial ocular amyloidosis involves the accumulation of proteins similar to immunoglobulin.

Lack of evidence for protein AA reactivity in amyloid deposits of lattice corneal dystrophy and amyloid corneal degeneration

Amyloid fibrils occurring in primary and myeloma-associated (AL), secondary (AA), and certain neuropathic hereditary forms of systemic amyloidosis can be distinguished biochemically or immunohistologically as being composed of immunoglobulin light chain, protein AA, or prealbumin respectively. All types of systemic and several localized forms of amyloidosis contain amyloid P component (protein AP). We studied formalin-fixed tissue from eight cases of lattice corneal dystrophy by the immunoperoxidase method using antisera to proteins AA and AP, to normal serum prealbumin and prealbumin isolated from a case of hereditary amyloidosis, and to light-chain determinants; additional cases were examined by indirect immunofluorescence of fresh-frozen material. We found weak (1:10 dilution) staining with anti-AP, but no reactivity with other antisera. Congo red staining was resistant to pretreatment of sections with potassium permanganate, a characteristic of non-AA amyloid. Two-dimensional gels of solubilized proteins from frozen tissue from two cases of lattice corneal dystrophy resembled those obtained from normal human cornea. Western blots of two cases of polymorphous amyloid degeneration and solubilized protein from normal cornea did not react with radioactive iodine-labeled anti-AA or anti-AP with purified protein AP and unfixed protein AA amyloid tissue as controls. We were unable to corroborate the presence of protein AA in the amyloid deposits of lattice corneal dystrophy. Although staining with antiserum to protein AP was demonstrable, the molecular configuration of this protein in stromal deposits remains to be defined.

Immunohistochemical demonstration of amyloid P component in cerebro-vascular amyloidosis

The presence of amyloid P component (AP) in cerebral amyloid deposits was sought using a direct immunoperoxidase technique. AP was detected in the amyloid deposits in the vessel walls but was absent from the intracerebral plaques in tissue from patients with senile cerebral amyloidosis. AP was also present in the amyloid deposits in the vessel walls of patients with the Icelandic form of hereditary cerebral haemorrhage associated with amyloidosis.

Immunohistochemical identification of the AA protein in lattice dystrophy

We examined the amyloid deposits of lattice dystrophy type I for common components of primary and secondary amyloid using the sensitive unlabelled antibody peroxidase-antiperoxidase technique. Tissue sections of formalin-fixed, paraffin-embedded specimens from three patients with lattice dystrophy were reacted with antisera specific for free immunoglobulin light chains, prealbumin, amyloid A (AA) protein, and amyloid P (AP) protein. The lattice amyloid was positive for the AA protein associated with secondary amyloid. The deposits were also stained with the protein AP antiserum in each case. We were unable to detect the presence of immunoglobulin light chains associated with primary amyloid or prealbumin associated with another heredofamilial form of amyloid. Sera from two patients with lattice dystrophy were tested for the presence of the serum amyloid A related protein, the apparent precursor of AA amyloid, by immunoelectrophoresis and immunodiffusion. The sera showed no reaction with the AA antiserum with these techniques. Lattice amyloid differed from secondary systemic amyloid in the reaction with potassium permanganate. Congo red staining of lattice deposits was not abolished by treatment with potassium permanganate. Our findings suggest that the amyloid proteins in lattice dystrophy are antigenically similar to those of secondary amyloid and the hereditary form associated with familial Mediterranean fever.

C-reactive protein in human lattice corneal dystrophy

Lattice corneal dystrophy (LCD), an autosomal dominantly inherited disease, is characterized by a branching network of subepithelial and stromal amyloid deposits (1). Due to their small size and close association with stromal components and epithelial cells, their chemical composition is as yet undetermined. Amyloid deposits in other types of diseases have been found to contain amyloid P protein (AP). Serum amyloid P component (SAP) and C-reactive protein (CRP) resemble each other in molecular structure and amino acid sequence, but appear to be antigenically distinct (2-6). A humoral mediator most likely stimulates CRP release by hepatocytes and could be related to Interleukin-I synthesis from macrophages (4-6). Rabbit corneal epithelial cells also produced an Interleukin-I-like activity and contain a thymocyte activating cytokine (7). In this study, corneas from normal controls, primary LCD and recurrent LCD were fixed in formalin with lmM CaCl2 and tested with antibodies to CRP, AP and AA (non-immunoamyloid), using the immunoperoxidase technique. The stroma of LCD and normal corneas did not stain with antibodies to AP, AA or CRP. However, we now report that antibodies to CRP show immunospecific binding to the corneal epithelium in primary and recurrent LCD.

The association of amyloid P-component (AP) with the amyloid fibril: an updated method for amyloid fibril protein isolation

An amyloid fibril isolation procedure is proposed which uses citrate as well as saline washes to dissociate the calcium dependent linkage of amyloid P-component (AP) from the amyloid fibril. In two amyloid rich tissues, the amount of AP was quantitated in each saline and citrate wash and totalled 13.8% and 20.8% of the amyloid fibrils isolated. The amount of AP removed from these and 22 additional amyloid rich tissues was greater than had previously been recognized. AP protein was present in tissue only when amyloid fibrils were present. It could not be found in normal non-amyloidotic tissue, nor could it be found in tissue sediment after the fibrils were removed.