Chronic kidney disease, severe arterial and arteriolar sclerosis and kidney neoplasia: on the spectrum of kidney involvement in MELAS syndrome.

BACKGROUND: MELAS syndrome (MIM ID#540000), an acronym for Mitochondrial Encephalopathy, Lactic Acidosis and Stroke-like episodes, is a genetically heterogeneous mitochondrial disorder with protean manifestations and occasional kidney involvement. Interest in the latter is rising due to the identification of cases with predominant kidney involvement and to the hypothesis of a link between mitochondrial DNA and kidney neoplasia. CASE PRESENTATION: We report the case of a 41-year-old male with full blown MELAS syndrome, with lactic acidosis and neurological impairment, affected by the "classic" 3243A > G mutation of mitochondrial DNA, with kidney cancer. After unilateral nephrectomy, he rapidly developed severe kidney functional impairment, with nephrotic proteinuria. Analysis of the kidney tissue at a distance from the two tumor lesions, sampled at the time of nephrectomy was performed in the context of normal blood pressure, recent onset of diabetes and before the appearance of proteinuria. The morphological examination revealed a widespread interstitial fibrosis with dense inflammatory infiltrate and tubular atrophy, mostly with thyroidization pattern. Vascular lesions were prominent: large vessels displayed marked intimal fibrosis and arterioles had hyaline deposits typical of hyaline arteriolosclerosis. These severe vascular lesions explained the different glomerular alterations including ischemic and obsolescent glomeruli, as is commonly observed in the so-called "benign" arteriolonephrosclerosis. Some rare glomeruli showed focal segmental glomerulosclerosis; as the patient subsequently developed nephrotic syndrome, these lesions suggest that silent ischemic changes may result in the development of focal segmental glomerulosclerosis secondary to nephron loss. CONCLUSIONS: Nephron loss may trigger glomerular sclerosis, at least in some cases of MELAS-related nephropathy. Thus the incidence of kidney disease in the "survivors" of MELAS syndrome may increase as the support therapy of these patients improves.

Intrasinusoidal bone marrow infiltration and splenic marginal zone lymphoma: a quantitative study.

Intrasinusoidal infiltration (ISI) is a pattern of invasion that is rarely found on bone marrow (BM) biopsies, and is considered as a hallmark of splenic marginal zone cell lymphoma (SMZL). We analysed BM biopsies showing intrasinusoidal infiltration from 54 consecutive patients with different types of lymphoma to verify if ISI quantity was a diagnostic criterion for SMZL. There were 35 primary splenic lymphoma (PSL) and 19 non-PSL; 28 SMZL, three non-splenic MZL, six mantle cell, six small lymphocytic, four follicular, four diffuse large B cell, one peripheral T cell, one lymphoplasmacytic and one anaplastic large-cell lymphoma. The quantity of BM infiltrate was assessed on CD45, CD20 and CD3 stained sections. The mean percentage of total (TI) and intrasinusoidal (ISI) lymphocytes was calculated in 10 areas for each case. TI quantity was 21.57 in PSL and 35.05 in non-PSL (P = 0.04). ISI quantity was 5.23 in PSL and 7.62 in non-PSL (P = 0.08), 5.83 in SMZL and 2.83 in other types of PSL (P = 0.12), 4.46 in non-splenic MZL and 8.21 in other types of non-PSL (P = 0.28). No difference in ISI quantity was found among the lymphoma subtypes, either in PSL (P = 0.74) or non-PSL (P = 0.3). The data demonstrate that ISI quantity in BM biopsies is not a reliable diagnostic parameter for SMZL.