Membranous nephropathy: Treatment outline and risk stratification

An Unusual Progression of Membranous Nephropathy

Membranous glomerulopathy is one of the commonest causes of nephrotic syndrome and chronic renal insufficiency in adults. There has been documented evidence of a poorer prognosis with factors such as male gender, advanced age, increased blood pressure and persistent loss of proteins in the urine, but the overall prognosis of this condition is excellent. Herein, we present the case of a 20-year-old female patient who was diagnosed with primary membranous nephropathy. Normally, cases of primary membranous nephropathy have good outcomes with conservative management and immunosuppressants but our case had a worsening course and a delayed response even with immunosuppressive treatment. This case has been recorded due to its unusual presentation, unnatural course, and outcomes contrary to what is seen in routine clinical practice.

Clinical Management of Glomerular Diseases

Progressive glomerular damage can occur as a result of various etiologic factors including infections, medications, diseases, and autoimmune disorders. This article discusses the clinical management of the leading conditions associated with glomerular disease, including glomerulosclerosis, diabetic nephropathy, focal segmental glomerulosclerosis, and membranous nephropathy. Glomerular damage and disease progression may lead to end stage renal disease. Clinical management is individualized, as based on causative factors and clinical manifestations, with the overall goal of limiting glomerular damage. Collaborative and comprehensive care is imperative to improving patient outcomes.

Management of Membranous Nephropathy in Asia

BACKGROUND

Membranous nephropathy (MN) is the most common cause of nephrotic syndrome (NS) in adults, accounting for about 20.0% of all NS cases. With an increasing prevalence, especially in the elderly, it has received great attention in Asia.

SUMMARY

Recently, the prevalence of idiopathic MN (IMN) has significantly increased among the elderly people in Asia and other places in the world. Although the exact mechanism of IMN remains unveiled, the identification of new antigens such as PLA2R and THSD7A has greatly enhanced our understanding of its pathogenesis. However, consensus has not yet been reached for the treatment of IMN in Asia. For example, there are many choices of immunosuppressive agents, including corticosteroid monotherapy, corticosteroids combined with cytotoxic agents [such as alkylating agents, calcineurin inhibitors or mycophenolate mofetil (MMF)] or traditional Chinese medicine (triptolide, Shenqi and other Chinese herbal soups). Patients with IMN in Asia often have a favorable prognosis, and progression to end-stage renal disease is relatively uncommon compared to other populations.

KEY MESSAGES

The prevalence of MN has significantly increased in the last years. The treatment strategies for IMN have not reached consensus in Asia. Traditional Chinese medicine is generally preferred by the Chinese, and compelling results have been reported recently.

FACTS FROM EAST AND WEST

(1) The prevalence of IMN is increasing worldwide, particularly in elderly patients, and has been reported in 20.0-36.8% of adult-onset NS cases. The presence of anti-PLA2R antibodies in serum or PLA2R on renal biopsy is the most predictive feature for the diagnosis of IMN and is used in both the East and West; however, appropriate screening to rule out secondary causes should still be performed. (2) Several observational (nonrandomized) Asian studies indicate a good response to corticosteroids alone in IMN patients, although no randomized controlled trials have been done in Asian membranous patients at high risk of progression. Corticosteroid monotherapy has failed in randomized controlled trial studies in Western countries and is therefore not recommended. (3) Cyclophosphamide is the most commonly prescribed alkylating agent in Europe and China. Also, chlorambucil is still used in some Western countries, particularly in Europe. In North America, calcineurin inhibitors are the more common first-line treatment. (4) Cyclosporine is predominantly used as monotherapy in North America, although KDIGO (Kidney Disease: Improving Global Outcomes) and Japanese guidelines still recommend a combination with low-dose corticosteroids. Clinical studies both in Asia and Europe showed no or little effects of monotherapy with MMF compared to standard therapies. (5) There are encouraging data from nonrandomized Western studies for the use of rituximab and a few small studies using adrenocorticotropic hormone. Clinical trials are ongoing in North America to confirm these observations. These drugs are rarely used in Asia. (6) A Chinese study reported that 36% of IMN patients suffered from venous thromboembolism versus 7.3% in a North American study. Prophylactic anticoagulation therapy is usually added to IMN patients with a low risk of bleeding in both Eastern and Western countries. (7) The Chinese traditional medicine herb triptolide, which might have podocyte-protective properties, is used in China to treat IMN. An open-label, multicenter, randomized controlled trial showed that Shenqi, a mixture of 13 herbs, was superior to corticosteroids plus cyclophosphamide therapy to restore epidermal growth factor receptor in IMN patients, although proteinuria improvement was equal in the two groups. Importantly, Shenqi treatment induced no severe adverse events while standard therapy did.

IQGAP1 regulates actin cytoskeleton organization in podocytes through interaction with nephrin

Increasing data has shown that the cytoskeletal reorganization of podocytes is involved in the onset of proteinuria and the progression of glomerular disease. Nephrin behaves as a signal sensor of the slit diaphragm to transmit cytoskeletal signals to maintain the unique structure of podocytes. However, the nephrin signaling cascade deserves further study. IQGAP1 is a scaffolding protein with the ability to regulate cytoskeletal organization. It is hypothesized that IQGAP1 contributes to actin reorganization in podocytes through interaction with nephrin. IQGAP1 expression and IQGAP1-nephrin colocalization in glomeruli were progressively decreased and then gradually recovered in line with the development of foot process fusion and proteinuria in puromycin aminonucleoside-injected rats. In cultured human podocytes, puromycin aminonucleoside-induced disruption of F-actin and disorders of migration and spreading were aggravated by IQGAP1 siRNA, and these effects were partially restored by a wild-type IQGAP1 plasmid. Furthermore, the cytoskeletal disorganization stimulated by cytochalasin D in COS7 cells was recovered by cotransfection with wild-type IQGAP1 and nephrin plasmids but was not recovered either by single transfection of the wild-type IQGAP1 plasmid or by cotransfection of mutant IQGAP1 [△1443(S→A)] and wild-type nephrin plasmids. Co-immunoprecipitation analysis using lysates of COS7 cells overexpressing nephrin and each derivative-domain molecule of IQGAP1 demonstrated that the poly-proline binding domain and RasGAP domain in the carboxyl terminus of IQGAP1 are the target modules that interact with nephrin. Collectively, these findings showed that activated IQGAP1, as an intracellular partner of nephrin, is involved in actin cytoskeleton organization and functional regulation of podocytes.