Immunohistochemical identification of the AA protein in lattice 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.

An immunohistochemical study of gelsolin immunoreactivity in corneal amyloidosis

A variant of the actin-modulating protein gelsolin has recently been identified as a component of the amyloid deposits in familial amyloidosis, Finnish type (Meretoja's syndrome), and has been demonstrated immunohistochemically in amyloid deposits in the cornea, and in the skin, kidney, heart, thyroid gland, salivary gland, and rectum of patients with this disease. With the use of immunohistochemistry involving an antibody against gelsolin, we examined a corneal specimen from a patient with Meretoja's syndrome and 14 corneal specimens with lattice dystrophy type I, atypical lattice dystrophy, polymorphic amyloid degeneration, primary familial amyloidosis, or secondary corneal amyloidosis. Our results showed the presence of a gelsolin-related protein either within or around corneal amyloid deposits in nine of the 15 specimens and markedly increased anti-gelsolin immunoreactivity of the corneal keratocytes in 13 of the 15 diseased corneas. These data indicated that the accumulation of gelsolin may be seen in various forms of amyloidosis and may not be confined to Meretoja's syndrome.

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 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.

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.

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.

Lattice corneal dystrophy associated with familial systemic amyloidosis (Meretoja's syndrome)

A 79-year-old white man of Irish descent presented with lattice corneal dystrophy, blepharochalasis, and peripheral seventh cranial nerve palsies. Family studies revealed that his 23-year-old daughter had early lattice cornea dystrophy. The corneal button removed by penetrating keratoplasty exhibited characteristic amyloid accumulation by light and electron microscopy. Biopsy of the patient's normal appearing conjunctiva and skin of the lower lid revealed amyloid. Biopsy of the daughter's conjunctiva was negative for amyloid, but her lid skin had characteristic amyloid deposits by light and electron microscopy. Immunoperoxidase strains were negative for AA and AP and serum prealbumin and SAA proteins were normal. Meretoja's syndrome has rarely been described outside a small geographic region in Finland. The clinical and histopathologic findings of this entity are discussed and contrasted to isolated "lattice corneal dystrophy."

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.