Accumulating studies reveal normal complement levels in cases of pediatric IgA nephropathy with MPGN-like patterns [3, 4]. For example, Andeen et al. found that among 15 IgA-dominant MPGN patients without liver disease, 11 (73%) had nephrotic-level proteinuria, and the complement level was normal [5]. Here, we report a rare case of IgA-dominant MPGN with hypocomplementemia.

In IgA nephropathy, the alternative pathway is activated along the capillary wall and in the mesangium because of C3 deposits [6]; IgA1 deposits in the mesangium activates the alternative pathway, and IgA2 deposits activates the lectin pathway [7]. In our case, IgA2 staining was stronger than IgA1 staining, suggesting predominant IgA2 deposits. No symptoms and test results suggested infectious diseases before the onset of MPGN in this case, but a pathological condition might be related to the lectin pathway, in addition to the alternative pathway. Karashima et al. observed predominant IgA deposition on the glomerular capillary wall and IgA2 deposition in two cases of secondary MPGN caused by a congenital portosystemic shunt [8]. In those two cases, hyperammonemia, elevated bile acids, and symptoms associated with hyperammonemia were observed from one to several years after the occurrence of urinary protein. In our case, a congenital portosystemic shunt was not detected by abdominal ultrasonography, computed tomography, and blood tests.

Growth hormone (GH) treatment was initiated when the patient was 4 years and 5 months of age due to her short stature. Four cases of IgA nephropathy during GH treatment have been reported in Japan. All of these cases were undergoing current GH treatment. One of these patients had stopped GH treatment because a renal biopsy had shown diffuse mesangial proliferation with cellular crescents in more than 30% of the glomeruli [9,10,11,12]. In our case, GH therapy was completed 1 year and 2 months before the onset of MPGN, so the effect of GH therapy is considered to be low.

MPGN is a progressive primary glomerulonephritis that occurs primarily in children and young adults [13]. Many studies have demonstrated that pediatric MPGN patients with alternate-day prednisolone treatment have a good prognosis [14,15,16,17]. In addition, treatment options, including angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, immunosuppressive agents, plasma exchange, and anti-inflammatory agents, could be administered depending on the amount of urinary protein, renal impairment, and steroid response [18]. However, to date, a consensus has not yet been reached regarding the administration method and the therapeutic effect of steroids in MPGN patients, and few studies have examined CsA use in MPGN cases [19, 20]. In our case, after three courses of steroid pulse therapy and oral administration of prednisolone, the urinary protein levels did not decrease, and lisinopril and MZR were thus added. However, her urinary protein tests did not become negative, and hematuria persisted. Hence, we added two courses of steroid pulse therapy, and the immunosuppressive drug was changed from MZR to CsA. Finally, the patient was in remission. These findings suggest that CsA may be useful as an immunosuppressive agent in patients with refractory MPGN.

In conclusion, we report a case of MPGN with IgA deposits along the glomerular capillary wall and in the mesangial region. The treatment for this case was difficult and complicated, and the CsA treatment resulted in remission. Our findings suggest that CsA may be useful as an immunosuppressant against refractory MPGN.