MesoAmerican Nephropathy: A New Entity

Recently, endemic rates of chronic kidney disease (CKD) have been identified in plantation workers and young farmers in Central America. The clinical profile of these patients has not been well characterized and studies on the pathology of the underlying kidney disease have been lacking. In a recent article published in AJKD, collaborators from the Karolinska Institute in Sweden and the Hospital Nacional Rosales in El Salvador describe kidney biopsy findings from 8 patients with MesoAmerican Nephropathy (MeN) recruited from a nephrology unit in El Salvador. Dr. Annika Wernerson (AW), the article’s corresponding author, discusses these findings with eAJKD Contributor Dr. Navdeep Tangri (eAJKD).

eAJKD: What interested you in this disease, and how did this international collaboration come about?

AW: We became interested in the high burden of kidney disease in Central America after reviewing several reports from Nicaragua, Costa Rica, and El Salvador. While these studies described the patient population, biopsy findings were not well reported. At a recent annual meeting of the American Society of Nephrology (ASN), we met with Dr. Ricardo Leiva from San Salvador, and the collaboration between Karolinska and the Hospital Nacional Rosales began.

eAJKD: What is your opinion about the global health burden of MeN?

AW: There are indeed several published studies that highlight the high burden of this disease entity across Central America. We believe that this disease may be occurring in different countries with similar occupational hazards. At the recently conducted workshop on MeN in Costa Rica, we learned about populations in countries such as Sri Lanka which have similar clinical characteristics, and may have similar biopsy findings. As such, we believe that the newly defined disease entity may be underreported.

eAJKD: Can you describe some of the key clinical features of this patient population?

AW: The study population consisted of young and middle-aged men who worked in farms in El Salvador. These patients worked long days in the fields in high temperatures, and performed physical labor that may be quite exhausting. They often had high daily water intake, and took NSAIDS and herbal medications for musculoskeletal pain related to their occupation. Despite their decreased kidney function, the majority of the patients were not hypertensive. In addition, they did not have any significant proteinuria. Hypokalemia was common, and severe in 3/8 patients, possibly related to dehydration or salt deficiency.

eAJKD: Can you describe some of the key features of the kidney biopsies?

AW: All of the kidney biopsies in our series exhibited an extensive degree of global glomerulosclerosis. This was an unexpected finding and difficult to explain since there was no evidence for chronic glomerulonephritis and only mild vascular changes. Two of the patients also had segmental glomerular sclerosis in their kidney biopsies, but these patients did not have significant proteinuria or other features suggestive of idiopathic focal and segmental glomerulosclerosis (FSGS) as the underlying cause. Tubular atrophy and interstitial fibrosis were also common among all the patients, but were mild or moderate. In six of the eight patients, a varying number of vacuoles and fat droplets were found in the podocyte cytoplasm.

eAJKD: How do you reconcile the clinical and pathologic features of MeN?

AW: We believe that the clinical picture combined with the biopsy findings suggests MeN is a mixed disorder with chronic tubulointerstitial changes as well as primary glomerular damage. Several of the clinical features such as repeated dehydration, salt depletion, and NSAID use may lead to tubular and glomerular ischemia, and could potentially cause this pattern of injury. Importantly, these findings are not consistent with a chronic glomerulonephritis as an underlying cause, and do not support the use of corticosteroids, as active inflammation is not a prominent feature. Taken together, we believe that MeN is a new pathologic entity that deserves further study.

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