Multiple Myeloma–Associated Ig Light Chain Crystalline Cast Nephropathy

Two kinds of rare light chain cast nephropathy caused by multiple myeloma: case reports and literature review

“…LCCCs are usually formed in the distal tubules, but occasionally can also form in the proximal tubules [ 26 , 37 , 39 ]. The staining properties of the crystalline casts are the same as those of ordinary light chain protein casts, appearing eosinophilic by HE staining, polychromatic (mixed red and blue) or fuschinophilic by Masson trichrome staining, pale by PAS staining and lack argyrophilic by PASM staining [ 38 , 39 , 42 , 46 , 47 ]. If toluidine blue is used to stain semi-thin sections, the crystals appear blue with the best recognition effect [ 31 ].…”

“…If the microcrystals embolize the glomerular capillaries and cause their destruction, the crystals in the circulation enter Bowman’s space and the tubular lumen and then form crystalline casts in the distal tubules. In the literatures, LCCCs can appear in three states: LCCCs existing alone [ 36 – 39 , 42 , 43 ], LCCCs coexisting with light chain crystal deposits of the proximal tubular epithelial cells [ 25 , 27 , 31 , 33 , 40 ], and in a few cases, LCCCs coexisting with light chain crystal deposits of the renal small vessels, glomerular capillaries, Bowman’s space and even extrarenal tissues [ 26 , 29 , 30 , 32 , 34 , 35 , 41 ]. These three states may provide some circumstantial evidence for the above three LCCC formation mechanisms.…”

“…However, it is said that LCCC was first reported by Löhlein in 1921 and published in a journal of pathology written in German [25]. In the published English literature, we retrieved 12 cases of LCCC confirmed by autopsy from 1949 to 1989 (one of the patients underwent renal biopsy before death) [25][26][27][28][29][30] and 27 cases of LCCC diagnosed by renal biopsy from 1987 to 2020 [31][32][33][34][35][36][37][38][39][40][41][42][43] (Table 2). Moreover, in two other papers, the authors mentioned that they also observed LCCC, but they did not provide detailed descriptions [44,45].…”

“…The crystals in LCCC vary in size and shape. These crystals can appear as needle-shaped, bar-shaped, spindle-shaped, diamond-shaped, triangle, rectangle, pentagon, hexagon and other geometric shapes [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43]. Some LCCCs are also surrounded by cellular reactions [25,26,28,31,32,37].…”

The Crystalline Nephropathies

“…However, the dysproteinemia may only be recognized after kidney biopsy. After work-up, ~80-90% of patients meet myeloma criteria (65). Other findings suggestive of myeloma such as hypercalcemia, bone pain, or anemia may also be present (65)(66)(67)(68)(69).…”