Objective: Systemic reactive AA amyloidosis is an intractable complication in patients with a long history of rheumatoid arthritis (RA). To help to more easily and reliably detect the presence of this form of amyloidosis in patients with RA and start intensive treatment as early as possible, we examined the sensitivity and usefulness of abdominal fat aspiration biopsy with phenol Congo red staining in the diagnosis of AA amyloidosis.
Patients and methods: Ten patients were diagnosed with systemic reactive AA amyloidosis secondary to RA (all women; mean age, 70.2 +/- 6.4 years; mean disease duration of RA, 20.3 +/- 11.2 years) based on histopathological examinations of biopsied specimens mainly from the gastroduodenal mucosa. Abdominal fat aspiration biopsy was performed in these patients, and the specimens were treated with both classical alkaline and phenol Congo red staining.
Results: Phenol Congo red staining revealed amyloid deposits in all 10 patients, while conventional alkaline Congo red staining showed a positive result in 7 patients. In the patients with a positive result with alkaline Congo red staining, reactivity of one grade or two higher was demonstrated by the phenol Congo red method.
Conclusion: Phenol Congo red staining is superior to the classical alkaline Congo red staining with respect to the detection of AA-amyloid deposits in biopsied abdominal fat tissue specimens. In addition to easy access and procedural safety, abdominal fat aspiration biopsy might contribute reliably to the diagnosis of systemic reactive AA amyloidosis secondary to RA when phenol Congo red staining is employed.