A 50-year-old male presented with signs and symptoms of restrictive heart disease. A right ventricular endo-myocardial biopsy revealed deposition of extracellular eosinophilic hyaline material. On transmission electron microscopy, this material is most likely to reveal the presence of-

Restrictive cardiomyopathy along with deposition of extracellular eosinophilic hyaline material suggest the diagnosis of Amyloidosis Myocardial involvement with amyloid is a common cause of secondary restrictive cardiomyopathy. Amyloid is a pathological proteinaceous substance deposited between cells in various tissues and organs of the body. With the light microscopic and standard tissue stains amyloid appears as an amorphous, eosinophilic, hyaline extracellular substance, that with progressive accumulation encroaches on and produces pressure atrophy of adjacent cells.