Morphological characteristics of the renal lesion in TAFRO syndrome and POEMS syndrome: a retrospective and multicenter study.

BACKGROUND

TAFRO syndrome (TAFRO) and POEMS syndrome (POEMS) are rare systemic inflammatory diseases with significant clinical, histological, and immunological overlaps with idiopathic multicentric Castleman disease (iMCD). While a high incidence of renal symptoms is observed in TAFRO and POEMS, the specific histopathological differences in their renal manifestations are not fully understood.

METHODS

This retrospective, multicenter study was conducted by the Japanese Renal Pathology Society (JRPS). Eighteen patients with TAFRO (n = 7), POEMS (n = 6), and iMCD (n = 5) were registered by members of the JRPS, and their clinicopathological findings were analyzed. Morphological examinations were performed using light, fluorescence, and electron microscopy. Immunohistochemical studies and semi-quantitative scoring systems have been used for detailed assessment of glomerular lesions.

RESULTS

Clinical data indicated that the time from disease onset to biopsy was significantly shorter in TAFRO patients than POEMS patients. Although immunosuppressive therapy induced improvement in all TAFRO patients, some POEMS patients exhibited a poor renal prognosis. Glomerular endothelial injury was observed in both the TAFRO and POEMS; however, the characteristics differed: the former displayed endotheliosis, whereas the latter exhibited membranoproliferative glomerulonephritis (MPGN)-pattern injury. Laminated short-linear structures of the subendothelial space were observed in both the TAFRO and POEMS using electron microscopy.

CONCLUSIONS

Morphological characteristics of the process of renal glomerular damage and repair in TAFRO and POEMS were revealed. The differences in endotheliosis and MPGN-pattern injury in these diseases may reflect differences in the timing of renal biopsy and the clinical course.