A Novel Method of DAPI Staining for Differential Diagnosis of Renal Amyloidosis
Motokazu Matsuura1,2, Hideharu Abe1, Tatsuya Tominaga1
1Division of Clinical Laboratory, Tokushima University Hospital.
Abstract:
Amyloidosis is often overlooked because its clinical manifestations can mimic those of more-common diseases. It is important to get a precise diagnosis as early as possible for the prevention of further organ damages. Amyloidosis is a disorder caused by deposition of insoluble abnormal amyloid. The kidney is a frequent site of amyloid deposition. The amyloid fibrils have a characteristic appearance and generate birefringence under polarized light when stained with the Congo red dye. Classification of amyloidosis is based on the precursor protein that forms the amyloid fibrils and the distribution of amyloid deposits as either systemic or localized. Involvement of amyloid fibrils in kidneys mainly occurs as amyloid light-chain (AL) or amyloid A (AA) amyloidosis. The potassium permanganate method with Congo red staining was once used widely to discriminate AL and AA amyloidoses, but this method has a problem of false positive results. We found that extracellular and cytoplasmic glomerular 4', 6-diamidino-2-phenylindole (DAPI)-positive areas were clearly consistent with amyloid deposition in AL amyloidosis. In contrast, the overlapping staining was not seen in AA amyloidosis. Therefore, we propose that DAPI staining readily distinguishes AL renal amyloidosis from AA renal amyloidosis as a simple and reproducible histochemical method. J. Med. Invest. 64: 217-221, August, 2017.
Insights
A new DAPI staining method accurately distinguishes amyloid light-chain (AL) amyloidosis from amyloid A (AA) amyloidosis in kidneys. This simple histochemical technique aids in early diagnosis to prevent organ damage.
Area of Science:
- Nephrology
- Histopathology
- Biochemistry
Background:
- Amyloidosis, caused by abnormal protein deposition, often presents with non-specific symptoms, delaying diagnosis and organ damage prevention.
- Kidney involvement is common in amyloidosis, primarily as amyloid light-chain (AL) or amyloid A (AA) types.
- Distinguishing between AL and AA renal amyloidosis is crucial for appropriate management, but traditional methods like potassium permanganate and Congo red staining can yield false positives.
Purpose of the Study:
- To develop and validate a simple, reproducible histochemical method for differentiating AL renal amyloidosis from AA renal amyloidosis.
- To assess the utility of 4', 6-diamidino-2-phenylindole (DAPI) staining in distinguishing these two types of renal amyloidosis.
Main Methods:
- Utilized 4', 6-diamidino-2-phenylindole (DAPI) staining on kidney tissue samples.
- Examined extracellular and cytoplasmic glomerular areas for DAPI-positive staining.
- Compared DAPI staining patterns with amyloid deposition in known cases of AL and AA amyloidosis.
Main Results:
- DAPI-positive areas in extracellular and cytoplasmic glomerular regions were consistently observed in AL renal amyloidosis.
- Overlapping DAPI staining was not observed in AA renal amyloidosis cases.
- The DAPI staining method demonstrated clear distinction between AL and AA renal amyloidosis.
Conclusions:
- 4', 6-diamidino-2-phenylindole (DAPI) staining is a reliable and simple histochemical method for distinguishing AL renal amyloidosis from AA renal amyloidosis.
- This technique offers a reproducible approach to improve diagnostic accuracy for renal amyloidosis.
- Early and precise diagnosis of renal amyloidosis subtypes can aid in preventing further organ damage.
