RESUMO
La amiloidosis se caracteriza por el depósito de proteínas de características ultraestructurales fibrilares, con plegamiento Beta en capas e insolubles, que se depositan mayoritariamente a nivel de los espacios extracelulares de órganos y tejidos. Se clasifica típicamente según la naturaleza bioquímica de la proteína fibrilar, y según su distribución en el organismo podrá ser sistémica o localizada. La amiloidosis sistémica más frecuente en la práctica clínica es la denominada AL (idiopática primaria o asociada a mieloma múltiple) cuyas fibrillas están formadas por cadenas ligeras. En cambio, la amiloidosis AA (secundaria, reactiva o adquirida) es aquella que se desarrolla típicamente como complicación de una enfermedad inflamatoria crónica, destacando entre las más habituales; enfermedades de origen reumatológico (artritis reumatoide, espondilitis anquilopoyética, artritis psoriásica), la fiebre mediterránea familiar, la enfermedad inflamatoria intestinal, así como infecciones cronificadas (tuberculosis, osteomielitis). No obstante, otras causas responsables de su desarrollo y en muchas ocasiones infravaloradas, son las tumoraciones benignas. Algunas de estas entidades, también tendrán capacidad de actuar como estímulo responsable de la formación de estas proteínas, que finalmente se depositarán en diferentes tejidos del organismo. Es importante resaltar, que el diagnóstico precoz así como el tratamiento eficaz de la enfermedad subyacente ha permitido disminuir su incidencia, así como en algunos casos incluso revertirla. Aquí, presentamos dos casos clínicos paradigmáticos de tumoraciones benignas, adenoma hepático y Enfermedad de Castlemann, que desarrollaron posteriormente amiloidosis AA con afectación renal principalmente en forma de síndrome Nefrótico (AU)
Amyolidosis is a systemic disorder characterized by the extracellular tissue deposition of insoluble, toxic aggregates in bundles of Beta-sheet fibrillar proteins. These deposits are typically identified on the bases of their apple-green birrefringence under a polarized light microscope after staining with Congo red, and by the presence of rigid, non branching fibrils 8 to 10 nm in diameter on electron microscopy. The type of amyloid fibril unit can be further defined by immunohistology or by immunoelectron microscopy. It has been described at least 25 different human protein precursors of amyloid fibrils, which will describe its corresponding amyloid disease. The most common types of amyloidosis are AL (primary) and AA (secondary) types; the former, is the most frequent and is due to deposition of proteins derived from immunoglobulin light chain fragments, occurring alone or in association with multiple myeloma. The later (AA), is caused by deposition of fibrils composed of fragments of the acute phase reactant serum amyloid A (SAA) and complicates chronic diseases with ongoing or recurring inflammation, namely; rheumatoid arthritis (RA), juvenile chronic polyarthritis, ankylosing spondylitis, familial periodic fever syndromes (Familial Mediterranean Fever), chronic infections and furthermore, some neoplasms (mainly renal cell carcinoma and Hodking¿s disease). Despite its less frequent association, some benign neoplasms can subsequently complicate to AA amyloidosis, therefore, an early diagnose and successful treatment may lead indeed, to regression of the amyloid disease. Herein, we present two cases of AA amyloidosis, both of them caused by 2 different benign neoplasms: 1. A 34 year-old woman, after chronic oral contraceptive use, developed an hepatic adenoma (fig. 1) which finally lead to AA amyloidosis with primary kidney presentation (pure nephrotic syndrome) (table 1). Post-surgical complications yield to acute renal failure from which unfortunately could not be recovered. After being on hemodialysis therapy during 10 months she received a first renal allograft without any complication. 2. A 20 yearold woman, was diagnosed of AA amyloidosis after a renal biopsy (fig. 2) because of nephrotic syndrome (table 1). Further investigation lead to the finding of a hialyne-vascular type Castleman¿s disease located in the retroperotoneum (fig. 2). Despite surgical resection and medical treatment (colchicine) she developed progressive renal failure requiring initialization of hemodialysis therapy. After 6 years being on hemodialysis, she received a first renal allograft which is currently functioning after one year of follow- up. Although other chronic inflamatory diseases complicate more frequently to AA amyloidosis, benign tumors have to be taken into account as a potential ethiological cause for secondary amyloidosis (AU)
