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Abstract
The diagnosis of amyloidosis (A) is confirmed by the deposit of amyloid with the Congo red stain in the biopsy of the organ that is suspected to be affected. The identification of the amyloid protein (PA) is necessary to guide the treatment. In Argentina we do not have techniques such as mass spectrometry (EM) or electron microscopy (EM) with immunohistochemistry, so we designed a systematic to arrive at the diagnosis.
Design: ambispective cohort of consecutive patients with diagnosis of A by biopsy of the Institutional Registry of Amyloidosis of the Hospital Italiano de Buenos Aires (RIA), 01/04 / 2012-7 / 2017. The evaluation consisted of: free light chains in serum and urine, the detection of clonality of plasma cells in bone marrow, measurement of SAA, and sequencing of the TTR gene.
Results: A total of 181 patients with A were included: 37% (67) AL, 16% (29) A Senile, 10% (19) AA, 4.4% (8) TTR mutated, 22.6% (41) A localized and in 9% (17) the responsible protein could not be identified. The 37% (67) met criteria for AL, 42% had a detectable monoclonal band corresponding to the isotypes L-lambda 44%, IgG-lambda 28 %, IgG-kappa 10%, L-kappa 6% and other isotypes 12%. Renal involvement was detected in 73% (49) and cardiac involvement in 66% (44). The differential diagnosis with A senil at the cardiac level was made with a PYP scintigraphy (negative in AL). In the A senil, 16% (29) presented TTR wild type. The cardiac commitment was 100% (29) and included biomarkers: ProBNP or BNP 100% (29/29) and compatible images in the echocardiogram 85% (23/27) and magnetic resonance 88% (24/27) . Cardiac scan with positive PYP.
The mutations detected in the hereditary TTR A were: 4 Val30Met (familial hereditary polyneuropathy, classic and late onset), 2 Thr60Ala (cardiac amyloidosis), 1 Ala36Pro (polyneuropathy), 1 Tyr114Cys (vitreous amyloidosis).
Of the cases of AA, 10% (19) yielded positive results in immunohistochemistry, of which 80% (15) had renal compromise, 26% (5) digestive, 21% (4) cardiac, and the dose of SAA was useful for follow up.
Conclusion: the characterization of the protein involved in the disease is important because it determines treatment and prognosis. The lack of the tools that allow this detection in the clinical laboratory led us to elaborate a detection system that allowed us to determine the involved protein with the available tools.
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