Etiological Spectrum and Histopathological Diagnosis of Rhabdomyolysis Associated Myoglobin Cast Nephropathy in South India

Background and Aims:

Rhabdomyolysis occurs due to injury to skeletal muscle fibers and the release of muscle constituents into the circulation. Myoglobin cast nephropathy leading to acute kidney injury is one of the most severe complications of rhabdomyolysis. This is a retrospective study which aims to analyse the clinicopathological features of myoglobin cast nephropathy.

Methods:

A total of 57 cases of myoglobin cast nephropathy were identified after performing immunohistochemical staining for myoglobin on all renal biopsies with pigment casts. The clinical, laboratory data, histopathological findings and clinical outcome of these cases were evaluated.

Results:

The mean patient age was 34.47 years (range 17-77) and the male to female ratio was 6.1:1. All patients presented with acute kidney injury with mean serum creatinine of 8.4 mg/dl (range: 1.7 to 20.8 mg/dl). Rhabdomyolysis was clinically suspected only in 31 patients. Along with myoglobin casts, acute tubular injury was present in all the biopsies. The most frequent conditions associated with myoglobin cast nephropathy in our study were snake envenomation and unaccustomed physical activities. A few activities that caused rhabdomyolysis in our patients were unique to India.

Conclusion:

Clinicians should be aware of the wide spectrum of causes for rhabdomyolysis. The classical clinical and laboratory findings of rhabdomyolysis may not be present in many of the patients. The pathologist must have a high index of suspicion, and immunohistochemical stain should be used to confirm the diagnosis.

Atheroembolic Renal Disease: A Case Series

Atheroembolic renal disease (AERD), a part of systemic cholesterol embolization syndrome, is caused by the occlusion of small arteries in the kidneys by cholesterol crystal emboli from ulcerated atherosclerotic plaques. Kidney is commonly involved because of its proximity to the abdominal aorta and its enormous blood supply. AERD is an under diagnosed condition. We report eight cases of AERD, highlighting the variability in its clinical presentation and the importance of a renal biopsy to arrive at a definitive diagnosis.

Dense deposit disease: a greatly increased biopsy incidence in India versus the USA

Background

We present the largest clinicopathologic case series to date of dense deposit disease (DDD) in an Indian population and compare the renal biopsy incidence rate to that seen in a large renal laboratory in USA.

Methods

Cases of DDD were identified and evaluated from native kidney biopsies reported at Renopath, India and at Arkana Laboratories, in the USA. Renopath receives biopsies from four states, located in the South and Eastern part of India. Arkana Laboratories’ biopsies came from 37 states across the USA.

Results

During the study period, there were a total of 25 patients diagnosed with DDD among the 7335 native kidney biopsies at Renopath. Thus, the biopsy incidence rate (cases of DDD/total renal biopsies/year) is 0.0034. By comparison, there were 10 cases of DDD diagnosed among 26 319 native kidney biopsies at Arkana Laboratories during the same time period, with a renal biopsy incidence rate of 0.00038.

Conclusions

DDD in this Indian subpopulation has similar clinical and pathologic characteristics when compared to previously reported studies. However, the biopsy incidence rate is about 890% or 8.9 times more common in this subset of the Indian population when compared with a broad cross-section of the US population. In addition to potential genetic factors, environmental conditions and chronic infections likely contribute to the markedly higher biopsy incidence rate. Given the much greater number of patients with DDD in this population, further retrospective and prospective studies would allow more rapid progress in understanding the pathogenesis of DDD and thus potential treatment of patients with DDD.

Cytomegalovirus Induced Collapsing Glomerulopathy and Necrotizing Glomerulonephritis in a Renal Allograft Recipient

In renal allograft recipients, cytomegalovirus (CMV) typically causes tubulointerstitial nephritis. Only rarely glomeruli are involved. We present a rare case of CMV with collapsing glomerulopathy, necrotizing glomerulonephritis, and crescent formation in a renal allograft recipient. Immunohistochemistry confirmed CMV infection. The patient was started on valganciclovir and his renal function remained stable. A repeat renal biopsy performed three months later showed morphologically normal glomeruli and CMV immunostaining was also negative. Nephropathologists have to carefully screen for CMV in cases with crescentic or collapsing glomerulopathy as the later lesions resolve after treating the underlying viral infection. This study will add on to the various glomerular changes associated with CMV infection.

Renal cell carcinoma with t(6,11): A case report and review of literature

Renal cell carcinomas (RCCs) with t(6,11) are very rare tumours. Only a few cases have been reported so far. t(6,11) results in fusion of alpha gene and transcription factor EB (TFEB) gene resulting in the overexpression of TFEB. The specific light and immunohistochemical features help in the diagnosis of this rare type of tumor. We report a case of t(6,11) RCC in a 38-year-old female who was incidentally found to have a right renal mass. We present this case to emphasize the typical light microscopic picture of this extremely rare tumor. Two population of cells are seen: larger cells with abundant cytoplasm and smaller cells with scant cytoplasm. Smaller cells are arranged around hyaline nodules resulting in the formation of characteristic pseudorosettes. Immunohistochemically, these tumors are diffusely positive for vimentin and focally positive for HMB 45 and CD 117. Knowledge about the typical biphasic light microscopic appearance and the characteristic immunohistochemical features help in the diagnosis of this rare type of translocation associated RCC.