Discordant renal histopathologic findings and complement profiles in membranoproliferative glomerulonephritis type III

Role of properdin in complement-mediated kidney diseases

As part of the innate immune system, the complement system is an important mechanism in our first line of defence, but it can also contribute to the onset of various diseases. In renal diseases, the dysregulation of the complement system is often caused by mutations in-and autoantibodies directed against-members of the complement system, and contributes to disease onset and severity. As the only known positive regulator of the complement system, the role of properdin in complement-mediated diseases is largely unknown. In this review, we provide an overview of the detection of properdin in kidney biopsies and urine, serum or plasma samples from patients with complement-mediated renal diseases, such as immune complex-mediated glomerulonephritis and C3 glomerulopathy. Advances towards a better understanding of the role of properdin in (local) complement activation will provide insight into its potential role and offer opportunities to improve diagnosis and therapeutic interventions.

Atypical glomerulopathy associated with the cblE inborn error of vitamin B₁₂ metabolism

BACKGROUND

The cblE disorder is an inherited disorder of vitamin B12 metabolism that results in elevated levels of homocysteine and decreased methionine in body fluids. Renal complications have been reported in patients with cblC disease, but not in those with cblE disease. The renal complications of cblC disease include thrombotic microangiopathy (TMA), neonatal hemolytic uremic syndrome, chronic renal failure, tubulointerstitial nephritis and proximal renal tubular acidosis. Previously, we reported a patient with cblC disease who had an atypical glomerulopathy that manifested with proteinuria and progressive renal insufficiency.

CASE-DIAGNOSIS/TREATMENT

Studies were done on cultured fibroblasts. Renal biopsy tissue was examined by light and electron microscopy. There was decreased incorporation of labeled methyltetrahydrofolate and decreased synthesis of methylcobalamin. Complementation analysis placed the patient into the cblE complementation group. The findings from the histological and ultrastructural studies of renal biopsy were similar, but not identical, to those of idiopathic membranoproliferative glomerulonephritis (MPGN) and overlapped with those of TMA.

CONCLUSIONS

We describe a patient with cblE disease who had an atypical glomerulopathy similar to MPGN. Additional findings included migraine headaches, hypothyroidism and livedo reticularis.