Background Different types of amyloid deposits may exist simultaneously in patients with rheumatoid arthritis (RA).
Objectives The aim of this study was to determine the types of amyloid deposits, i.e. the spectrum of amyloidosis, in RA.
Methods A randomized autopsy population of 161 in-patients with RA was studied. The patients died at the National Institute of Rheumatology between 1969 and 1992.
RA was confirmed clinically according to the criteria of ACR. Amyloid deposits in 25 organs [gastrointestinal tract, heart, urogenital organs (kidney, prostate, seminal vesicles, testis and epididymis, uterus and adnexa), spleen, adrenal glands, liver, pancreas, lungs, thyroid gland, aorta, skeletal muscles, synovial membranes, lymph nodes, peripheral nerves, bone (head of femur), skin and brain] were determined histologically.
Results Different types of amyloid deposits existed simultaneously in the same patient. Systemic secondary AA amyloidosis (AAa) was present in 34 (21.12%), systemic primary myeloma-associated immunoglobulin AL k-chain amyloidosis in 1 (0.62%) of 161, cerebral b protein-related amyloidosis (cerebral amyloid angiopathy – CAA) in 2 (3.77%) of 53*, dystrophic (aging related) linear or globular amyloid deposits localized to the superficial zone of articular cartilage in 9 (16.98%) of 53*, endocrine related prohormone fragments localized to islets of Langerhans (Islet amyloid polypeptide – AIAPP) in 13 (11.71%) of 111*, b2 microglobulin amyloid (Ab2M) localized to the kidney in 1 (0.63%) of 159*, and prostatic in 6 (54.55%) of 11*, or pulmonary corpora amylacea (b2-microglobulin – Ab2M) in 8 (5.75%) of 139* patients were present.
(*Some organs of 161 RA patients were not available for evaluation.)
Conclusions Only AA amyloidosis may be considered as a true complication of RA, any other types of amyloidosis may be present in RA as an associated phenomenon or complication of associated diseases .
The low prevalence of systemic primary AL k-chain amyloidosis has been deceptive in our autopsy population. One recognized reason has been that patients with lymphoproliferative disorders were transferred to an institution specialized in hematology.
It is difficult to estimate the true prevalence of AAa in RA. The prevalence of amyloidosis depends on the specificity and sensitivity of the applied method. Using a less sensitive staining method some positive cases remain undetected. A more specific method potentially detects more cases, and reveals earlier stages. Older methods are less specific in comparison with Congo red staining applied by Puchtler et al. . Congo red staining according to Romhányi is a more specific and sensitive method for detection of amyloid deposits in comparison with Puchtler's Congo red methods .
Less extensive postmortem examination (of fewer organs with a different prevalence of AAa) may explain differences of prevalence and incidence as well.
Bély M, Apáthy Ά: Clinical pathology of rheumatoid arthritis: Cause of death, lethal complications and associated diseases in rheumatoid arthritis. 1-440 pp. Akadémiai Kiadό, Budapest 2012 http://www.akkrt.hu
Puchtler H, Sweat F, Levine M: On the binding of Congo red by amyloid. J Histochem Cytochem, 1962; 10:355-364
Bély M, Makovitzky J: Sensitivity and Specificity of Congo red Staining According to Romhányi - Comparison with Puchtler's or Bennhold's Methods. Acta Histochemica, 2006; 108:175-180
Disclosure of Interest None declared