A 50-year-old male presented with signs and symptoms of restrictive hea disease. A right ventricular endomyocardial biopsy revealed deposition of extracellular eosinophilic hyaline material. On transmission electron microscopy, this material is most likely to reveal the presence of
**Core Concept**
Restrictive cardiomyopathy is a condition characterized by the stiffening of the heart muscle, leading to impaired diastolic function. In this case, the presence of extracellular eosinophilic hyaline material suggests a specific type of restrictive cardiomyopathy associated with the deposition of abnormal protein material.
**Why the Correct Answer is Right**
The extracellular eosinophilic hyaline material seen in this case is likely to be composed of amyloid fibrils. Amyloidosis is a condition where abnormal protein fibrils accumulate in various tissues, including the heart. The presence of amyloid fibrils can lead to the stiffening of the heart muscle, resulting in restrictive cardiomyopathy. On transmission electron microscopy, amyloid fibrils appear as non-branching, straight fibrils with a diameter of 7-10 nanometers.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the material in question is not composed of collagen, which is a type of protein found in connective tissue. While collagen deposition can also lead to restrictive cardiomyopathy, the specific histological features described in this case are more consistent with amyloidosis.
**Option B:** This option is incorrect because the material is not composed of lipids, which are fat-soluble molecules. While lipid deposition can occur in various cardiac conditions, the extracellular eosinophilic hyaline material seen in this case is more likely to be composed of amyloid fibrils.
**Option C:** This option is incorrect because the material is not composed of glycogen, which is a type of carbohydrate storage molecule. While glycogen accumulation can occur in certain cardiac conditions, the specific histological features described in this case are more consistent with amyloidosis.
**Clinical Pearl / High-Yield Fact**
Amyloidosis can be classified into various subtypes based on the type of protein fibril deposited, including light-chain amyloidosis, transthyretin amyloidosis, and wild-type transthyretin amyloidosis. Each subtype has distinct clinical features and prognostic implications.
**Correct Answer:** D.