Immunoglobulin A nephropathy (IgAN) is a glomerulopathy characterized by the presence of mesangial deposits of IgA, either alone or showing predominance over other immunoglobulins.1 The pathological study enables the diagnosis and evaluation of the disease activity. Its association with rheumatic diseases has been reported2,3; however, the pathophysiological relationship is still not clear.1,4 For the purpose of establishing the prevalence, clinical features, analytical findings, treatment and outcome of IgAN in a cohort of patients with rheumatic disease, we conducted a retrospective study (1984–2014) in a university hospital serving a population of 850000. We reviewed the pathological diagnoses of 27,215 patients being treated in the rheumatology department and selected those with a histological diagnosis of IgAN. We excluded the patients in whom the only rheumatic disease diagnosed was gout, osteoporosis or noninflammatory disease. We identified 6 patients (0.025%), all men. Of 1110 patients with rheumatoid arthritis, 2 (0.009%) had been diagnosed with IgAN. Of 287 patients with ankylosing spondylitis, 2 (0.69%) had IgAN. Only 1 (0.17%) of the 558 patients with psoriatic arthritis had received a diagnosis of IgAN, as was the case of 1 of the 13 patients (0.7%) with undifferentiated connective tissue disease. The mean age at the diagnosis of IgAN and of the rheumatic disease was 46.7 and 37 years, respectively (range: 34–54 and 18–67 years). The mean duration of the rheumatic disease prior to the diagnosis of IgAN was 15.4 years. Hematuria (100%), renal failure (100%) and nephrotic syndrome (8.6%) were the signs that led to the suspicion of the presence of IgAN. All 6 patients had hypertension and 8.6% had nephrotic-range proteinuria. The mean values of serum creatinine and 24-h proteinuria at the time of the diagnosis of IgAN were 1.85mg/dL (range: 1.5–2.5) and 1.94g (range: 0.8–4.12), respectively. Over the course of the disease, 3 patients (50%) required hemodialysis after a mean period of 5.6 years since the diagnosis (range: 2–11); all 3 underwent renal transplantation within an interval of 9–25 months after starting hemodialysis. One patient (16.6%) died at the age of 60 years (7 years after the diagnosis of IgAN) due to sepsis of pulmonary origin. During follow-up, the mean creatinine levels of the patients who did not receive dialysis was 1.4mg/dL (range: 1.1–1.6); they were treated medically (angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers).

The prevalence of IgAN in the general population is 25–50 cases per 100000 population5 and, although in the majority of the patients with chronic inflammatory arthropathy, renal involvement is secondary to amyloidosis or an adverse drug reaction,2,3 there are reports that indicate the possible relationship between rheumatic diseases and IgAN.6,7 Given the prevalence of IgAN in the general population, in some cases, its coexistence with a rheumatic disease may be coincidental. In patients with spondyloarthropathies, the relationship would be explained by the reported change in the catabolism of glycoprotein receptors and IgA-specific receptors (FcαR or CD89) found in tissue and peripheral blood.6,7

The results of the present study do not differ from previous findings reported in the literature.5 The prevalence is higher in men and the clinical presentation is characterized by proteinuria, hypertension and hematuria. The cohort of patients of Azevedo et al.5 showed a higher frequency of calcaneal enthesitis and anterior uveitis. In accordance with our observations, in clinical practice, the diagnosis of IgAN should be considered in patients with a rheumatic disease who develop hematuria, proteinuria, renal failure and hypertension during the course of their disease.