Cellular events associated with the initial phase of AA amyloidogenesis: insights from a human monocyte model.

Reactive amyloidosis is a systemic protein deposition disease that develops in association with chronic inflammation. The deposits are composed of extracellular, fibrillar masses of amyloid A (AA) protein, an N-terminal fragment of the acute-phase serum protein serum amyloid A (SAA). The pathogenic conversion of SAA into amyloid has been studied in two human cell culture models, peritoneal cells and peripheral blood monocytes. Human monocyte cultures proved more robust than either mouse or human peritoneal cells at initiating amyloid formation in the absence of a preformed nidus such as amyloid-enhancing factor and particularly well suited for examination of individual cells undergoing amyloid formation. Amyloid-producing monocyte cultures were stained with Congo red and Alcian blue for detection of amyloid and glycosaminglycans, respectively; immunocytochemistry was performed to identify SAA/AA, CD68, CD14, lysosomal protein Lamp-1, and early endosomal protein EEA1. SAA interaction with monocytes was also visualized directly via fluorescence confocal microscopy. Amyloid was initially detected only in intracellular vesicles, but with time was seen extracellularly. Morphologic changes in lysosomes were noted during the early phase of amyloid formation, suggesting that exocytosis of fibrils may occur via lysosome-derived vesicles. Cultures engaged in amyloid formation remained metabolically active; no cytotoxic effects were observed. Mimicking in vivo phenomena, amyloid formation was accompanied by increased glycosaminoglycan content and C-terminal processing of SAA. The ability of human monocytes to endocytose and intracellularly transform SAA into amyloid via a mechanism that requires and maintains, rather than compromises, metabolic activity distinguishes them as a useful model for probing earliest events in the disease process.

Neurological manifestations and neuroradiological presentation of Erdheim-Chester disease: report of 6 cases and systematic review of the literature.

Erdheim-Chester disease (ECD) is a rare, non-Langerhans form of histiocytosis of unknown etiology that affects multiple organs. We report 6 cases of ECD with neurological involvement and neuroradiological abnormalities on brain MRI. A literature review revealed 60 other cases of ECD with neurological involvement. We therefore analyzed 66 ECD patients with neurological involvement. Cerebellar and pyramidal syndromes were the most frequent clinical manifestations (41% and 45% of cases), but seizures, headaches, neuropsychiatric or cognitive troubles, sensory disturbances, cranial nerve paralysis or asymptomatic lesions were also reported. Neurological manifestations were always associated with other organ involvement, especially of bones (at least 86%) and diabetes insipidus (47%). Neurological involvement was responsible for severe functional handicaps in almost all patients and was responsible for the death of 6 of the 66 patients (9%). Neuroradiological findings could be separated into three patterns: the infiltrative pattern (44%), with widespread lesions, nodules or intracerebral masses, the meningeal pattern (37%), with either thickening of the dura mater or meningioma-like tumors, and the composite pattern (19%), with both infiltrative and meningeal lesions.

Detection of a mesenchymal tumor responsible for hypophosphatemic osteomalacia using FDG-PET.

We report a case of oncogenic osteomalacia (OO) in a 71-year-old man. The tumor, which was localized in the left lower mandible, was not found by CT, MRI, or 111-indium octreotide scintigraphy but was easily detected by FDG-PET. The use of this technique in OO has never been reported.

Amyloid-enhancing factor mediates amyloid formation on fibroblasts via a nidus/template mechanism.

OBJECTIVE: To determine the mechanism by which amyloid-enhancing factor (AEF) promotes amyloid deposition, and to test whether AEF seeds deposition of serum amyloid A (SAA) and facilitates conversion to beta-sheet structure. METHODS: Fibroblasts were cultured with mouse recombinant SAA1.1 and AEF, SAA1.1, or AEF. AEF was prepared as a glycerol extract of spleen from amyloidotic mice. Amyloid was identified by staining with Congo red and examining for green birefringence under polarized light. SAA was localized immunohistochemically. Texas Red-labeled SAA was visualized in living cultures by fluorescence confocal microscopy. AEF was characterized by Western blot analysis using anti-SAA antiserum and N-terminal sequence analysis. Subunits comprising amyloid in fibroblast cultures were characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. RESULTS: Amyloid was produced in fibroblast cultures by an AEF-dependent mechanism. AEF, added to culture medium as insoluble protein precipitates, adhered to fibroblast monolayers. SAA bound preferentially to the adherent precipitates. Coincident with SAA binding, precipitates developed an affinity for Congo red. Over time, as more SAA was added, networks of Congo red-positive material producing bright green birefringence also developed outward from AEF precipitates. Amyloid built upon AEF in this manner was composed of full-length SAA. No amyloid was produced in cultures treated with either SAA or AEF alone. SAA and SAA peptides processed in the C-terminal region were the most prominent proteins in the glycerol-extracted AEF preparation. CONCLUSION: AEF binds to fibroblast monolayers and acts as a sink for SAA. SAA that collects on AEF assembles into an amyloid structure. Thus, it is concluded that AEF serves as both a nidus and a template for amyloid formation.

A transthyretin mutation (Tyr78Phe) associated with peripheral neuropathy, carpal tunnel syndrome and skin amyloidosis.

BACKGROUND: More than 80 transthyretin (TTR) mutations have been described, most associated with amyloidosis. Peripheral neuropathy is the most common clinical presentation in TTR amyloidosis although the carpal tunnel syndrome (CTS) may be the first symptom and skin can be involved, as transthyretin amyloidosis is a systemic disease. CASE REPORT: The 78 year-old proband, belonging to a French family of Italian origin, presented with a 5 year history of peripheral neuropathy in the lower extremities. However, 15 years earlier he had had surgery for bilateral CTS. Amyloidosis was diagnosed on salivary gland and skin biopsies. Immunohistochemistry on skin biopsy was positive using anti-TTR. The proband has 10 siblings, 5 have CTS. METHODS: SSCP and direct sequencing of exons 2, 3, and 4 of the TTR gene were done on DNA from the proband and his brother who had had CTS. To confirm the mutation a PCR-IMRA was done. RESULTS: SSCP analysis of TTR exons 2, 3, and 4 did not suggest a mutation. Sequence analysis of TTR exon 3 revealed heterozygosity in both subjects for a single basepair transversion from A to T in codon 78 (TAC-->TTC) indicating a tyrosine to phenylalanine change. The mutation was confirmed by PCR-IMRA. CONCLUSION: This TTR mutation (Tyr78Phe) is associated with peripheral neuropathy, carpal tunnel syndrome and skin amyloidosis. It is also associated with late onset of the disease.

Renal transplantation for apolipoprotein AII amyloidosis.

Apolipoprotein AII (ApoAII) amyloidosis, first reported in 2001 in a family with renal amyloidosis, is associated with mutations in the stop codon of the apolipoprotein AII gene resulting in a carboxyl terminal peptide extension of 21 amino acid residues in the protein. Since death from this form of amyloidosis is due to renal failure, kidney dialysis and renal transplantation are presently the only two therapeutic options. We report the case of a Caucasian man who developed proteinuria in his late 20's, had renal biopsy at the age of 33 which gave the diagnosis of renal amyloidosis, and required continuous ambulatory peritoneal dialysis by age 45. He received a cadaver renal transplant at age 47 and has maintained stable renal function for nine years without other evidence for organ system dysfunction from amyloidosis. Laboratory studies confirmed persistence of the ApoAII variant in the patient's plasma in addition to the normal ApoAII protein. This is in agreement with the DNA analysis which showed the patient to be heterozygous for the ApoAII stop78Gly mutation. These results indicate that renal transplantation is an effective therapy for apolipoprotein AII amyloidosis since recurrence of amyloid in the graft and progression of other organ involvement may be very slow.

Transthyretin mutation (TTRGly47Ala) associated with familial amyloid polyneuropathy in a French family.

A French family in which three individuals had familial amyloid polyneuropathy (FAP) was investigated. The proband presented cardiomyopathy with atrial arrhythmia and then developed axonal polyneuropathy, carpal tunnel syndrome, and sclerodactyly. Nucleotide sequencing of exons 2, 3 and 4 of the transthyretin (TTR) gene revealed heterozygosity for a single base change in the second position of codon 47. This G to C transversion predicts replacement of a glycine by an alanine at position 47 in the mature protein. This mutation (G47A) was previously identified in two different families of Italian origin both of which had FAP and cardiomyopathy. Here we report the first identification of this mutation in a non-Italian family.

Laboratory assessment of transthyretin amyloidosis.

Mutations in transthyretin (TTR) are the most common cause of autosomal dominant systemic amyloidosis. To date, more than 80 TTR mutations have been associated with amyloidosis in humans. A high prevalence of some mutations like Val122Ile which is identified in 3% of African Americans indicates the necessity of thorough investigation of patients suspected of having, or to be at risk of developing, TTR amyloidosis. Laboratory tests available for evaluation of TTR amyloidosis include both DNA and protein assays. In the case of a known mutation DNA analysis is realized by restriction fragment length polymorphism (RFLP), polymerase chain reaction-induced mutation restriction analysis (PCR-IMRA), single strand confirmation polymorpism (SSCP) or nucleotide sequencing. SSCP, PCR-non-isotopic RNAse cleavage assay (NIRCA) or nucleotide sequencing are used to identify an unknown mutation. At the protein level, two techniques are used, isoelectric focusing and mass spectrometry, in both cases (known or unknown mutation). The identification of a previously unknown mutation requires a combination of clinical, pathological and molecular studies.