A recently deceased 92-year-old woman with a history of arrhythmia was discovered to have amyloid deposition in her atria upon autopsy. Upon further examination, there was no amyloid found in any other organs. The peptide at fault was identified and characterized by the pathologist performing the autopsy. Before its eventual deposition in the cardiac atria, which of the following functions was associated with the peptide?
1. Reduction of blood calcium concentration
2. Antigen recognition
3. Vasodilation
4. Slowing of gastric emptying
5. Stimulation of lactation
2. Antigen recognition
3. Vasodilation
4. Slowing of gastric emptying
5. Stimulation of lactation
DISCUSSION: Upon autopsy, this patient was discovered to have amyloid deposits in the cardiac atria but interestingly in no other organs. By definition, this is isolated atrial amyloidosis (IAA) which is primarily caused by deposition of atrial natriuretic peptide (ANP) associated proteins. The function of ANP is vasodilation and reduction of total body sodium and water, through increased renal excretion.
Amyloid is a generic term that refers to a group of diverse extracellular protein deposits. Although amyloids vary in amino acid sequence, all amyloid proteins are folded such that they share common ultrastructural and physical properties. All amyloids to be stain with congo red dye, which aids in diagnosis. Under polarized light, these deposits exhibit a red-green birefringence. In general, amyloidoses can be divided into systemic or isolated. By definition isolated amyloidosis is restricted to a single organ, as seen in this case as it is found only in the cardiac atria (isolated atrial amyloidosis).
Torricelli et al. report that alpha atrial natriuretic peptide is the protein responsible for isolated atrial amyloidosis upon histological evaluation of the myocardial tissue. This is unique to amyloid deposited only in the heart.
According to Steiner at al., autopsies reveal an 86% incidence of isolated atrial amyloidosis in those aged 81-90 years. This high frequency supports the idea that amyloid deposition is part of the senescence process of the heart.
Illustration A shows a myocardial tissue biopsy with amyloid deposition.
Illustration B shows a renal biopsy with congo red staining showing apple-green birefringence.
Incorrect answers:
Answer 1: Calcitonin reduces blood calcium and is commonly found in localized amyloidoses of the thyroid gland.
Answer 2: Immune globulin light chain is involved in antigen recognition and causes multi-organ amyloid deposition that is not restricted to the cardiac atria.
Answer 4: Amylin slows gastric emptying and is found in localized amyloidoses in the pancreas.
Answer 5: Prolactin stimulates lactation and is found in localized amyloidoses of the pituitary gland.
Amyloid is a generic term that refers to a group of diverse extracellular protein deposits. Although amyloids vary in amino acid sequence, all amyloid proteins are folded such that they share common ultrastructural and physical properties. All amyloids to be stain with congo red dye, which aids in diagnosis. Under polarized light, these deposits exhibit a red-green birefringence. In general, amyloidoses can be divided into systemic or isolated. By definition isolated amyloidosis is restricted to a single organ, as seen in this case as it is found only in the cardiac atria (isolated atrial amyloidosis).
Torricelli et al. report that alpha atrial natriuretic peptide is the protein responsible for isolated atrial amyloidosis upon histological evaluation of the myocardial tissue. This is unique to amyloid deposited only in the heart.
According to Steiner at al., autopsies reveal an 86% incidence of isolated atrial amyloidosis in those aged 81-90 years. This high frequency supports the idea that amyloid deposition is part of the senescence process of the heart.
Illustration A shows a myocardial tissue biopsy with amyloid deposition.
Illustration B shows a renal biopsy with congo red staining showing apple-green birefringence.
Incorrect answers:
Answer 1: Calcitonin reduces blood calcium and is commonly found in localized amyloidoses of the thyroid gland.
Answer 2: Immune globulin light chain is involved in antigen recognition and causes multi-organ amyloid deposition that is not restricted to the cardiac atria.
Answer 4: Amylin slows gastric emptying and is found in localized amyloidoses in the pancreas.
Answer 5: Prolactin stimulates lactation and is found in localized amyloidoses of the pituitary gland.
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