Yes, it is possible for a bone marrow biopsy to show Congo red-positive amyloid deposits without clonal plasma cells being detected on flow cytometry. This is actually one of the tricky aspects of diagnosing AL amyloidosis.
Here's why this can happen:
- Low-level clonal cells — The abnormal plasma cells may be present in Show Full Answer
Yes, it is possible for a bone marrow biopsy to show Congo red-positive amyloid deposits without clonal plasma cells being detected on flow cytometry. This is actually one of the tricky aspects of diagnosing AL amyloidosis.
Here's why this can happen:
- Low-level clonal cells — The abnormal plasma cells may be present in very small numbers, below the detection threshold of flow cytometry
- Uneven distribution — Plasma cells can be unevenly spread through the bone marrow, meaning the sample taken may not capture them
- Test sensitivity limits — Flow cytometry doesn't catch every case, and a negative result doesn't completely rule out a clonal plasma cell disorder When Congo red staining is positive (the sample appears green under a special microscope), that confirms amyloid deposits are present. Additional testing is usually recommended in this situation, such as:
- Serum free light-chain assay to detect abnormal light-chain proteins in the blood
- Immunofixation electrophoresis (IFE) on blood and urine
- Repeat or deeper bone marrow sampling
It's really important to work closely with a specialist experienced in amyloidosis, as piecing together multiple test results together gives the clearest picture. No single test tells the whole story.
July 24
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