New subcategories of class IV lupus nephritis: are there clinical, histologic, and outcome differences?

BACKGROUND: The International Society of Nephrologists and Renal Pathology Society (ISN/RPS) classification of lupus nephritis proposes a controversial subclassification of class IV lupus nephritis into IV-segmental (IV-S) and IV-global (IV-G).

METHODS: A retrospective analysis of a biopsy-proven cohort of patients with lupus nephritis using the ISN/RPS classification was performed.

RESULTS: The prevalence of class IV was 47% in the cohort of 70 patients with lupus nephritis. Of 33 patients with class IV lupus nephritis, 11 patients had class IV-S and 22 patients had class IV-G. There were no significant differences in age, sex, and ethnicity in the 2 groups. Greater serological activity (lower C4 level) was observed in the IV-S group, whereas serum creatinine levels and diastolic blood pressures were significantly greater in the IV-G group. Hematocrit levels, significant proteinuria (urine protein > or =3 + ), duration of systemic lupus erythematosus, and the Systemic Lupus Erythematosus Disease Activity Index were similar in the 2 groups. Histologically, combined lesions with segmental endocapillary proliferation and fibrinoid necrosis were significantly more frequent in the IV-S group. The percentage of glomeruli with cellular crescents also was greater in the IV-S group, but the difference was not significant. Wire loops were more common in the IV-G group. Transformation to IV-G was observed in 2 of 3 specimens from repeated biopsies available in the IV-S group; greater than 50% of the IV-G group had both segmental and global glomerular involvement. No significant difference was detected in outcomes in the 2 groups after average follow-ups of 38 and 55 months in the IV-S and IV-G groups, respectively.

CONCLUSION: A clinical and prognostic distinction between IV-S and IV-G remains to be proven.