Elena Levtchenko

Autosomal recessive inheritance of von Willebrand factor-cleaving protease deficiency

Abstractu2002A child with chronic relapsing thrombotic thrombocytopenic purpura (TTP/HUS) had recurrent thrombocytopenia, microangiopathic hemolytic anemia with fragmented erythrocytes, microthrombi in the lung vessels, and renal dysfunction. Assay of von Willebrand factor (vWF)-cleaving protease showed a complete protease deficiency in the patient and subnormal activities in the mother and in two asymptomatic siblings. No inhibitor of vWF-cleaving protease was detected in the patient’s plasma. Periodic transfusions of fresh-frozen plasma prevented further acute episodes of TTP/HUS. Specific diagnosis of the constitutional deficiency of vWF-cleaving protease helps to provide successful prophylactic therapy.

ACE inhibitorenalapril diminishes albuminuria in patients with cystinosis.

BACKGROUND/AIMSnCystinosis, a rare autosomal recessive disease, manifests with renal Fanconi syndrome during the first year of life. Interstitial damage is a major cause of renal failure in patients with cystinosis. We presume that albuminuria contributes to the development of renal failure in these patients. The aim of this study was to examine whether the administration of ACE inhibitor enalapril diminishes albuminuria in patients with cystinosis.nnnMETHODSnFive patients with cystinosis aged 4 - 9 years were studied. All patients had Fanconi syndrome and were treated with cysteamine. Median creatinine clearance was 48 ml/min/1.73 m2 (range 21 - 61). The excretion of albumin and alpha1 microglobulin as well as arterial blood pressure and serum creatinine were evaluated before and at 3 months on oral administration of enalapril (0.15 mg/kg once daily).nnnRESULTSnAt 3 months on enalapril, albuminuria decreased in all patients (1,042 vs 629 mg per 24 h, p < 0.05). The median reduction of albuminuria was 43% (range: 4 - 72%, p < 0.05). Urinary excretion of alpha1 microglobulin remained constant. Systolic blood pressure decreased from median 110 - 100 mmHg (p < 0.05), while diastolic blood pressure remained stable (median 60 mmHg). Creatinine clearance decreased from median 48 - 45 ml/min/1.73 m2 (p < 0.05) and returned to previous values after discontinuation of enalapril.nnnCONCLUSIONnACE inhibitor enalapril diminishes albuminuria in patients with cystinosis and might be used in these patients in order to slow the progression of renal insufficiency attributed to proteinuria.

Clinical utility of chitotriosidase enzyme activity in nephropathic cystinosis

BackgroundNephropathic cystinosis is an inherited autosomal recessive lysosomal storage disorder characterized by the pathological accumulation and crystallization of cystine inside different cell types. WBC cystine determination forms the basis for the diagnosis and therapeutic monitoring with the cystine depleting drug (cysteamine). The chitotriosidase enzyme is a human chitinase, produced by activated macrophages. Its elevation is documented in several lysosomal storage disorders. Although, about 6% of Caucasians have enzyme deficiency due to homozygosity of 24-bp duplication mutation in the chitotriosidase gene, it is currently established as a screening marker and therapeutic monitor for Gaucher’s disease.MethodsPlasma chitotriosidase activity was measured in 45 cystinotic patients, and compared with 87 healthy controls and 54 renal disease patients with different degrees of renal failure (CKD1-5). Chitotriosidase levels were also correlated with WBC cystine in 32 treated patients. Furthermore, we incubated control human macrophages in-vitro with different concentrations of cystine crystals and monitored the response of tumor necrosis factor-alpha (TNF-α) and chitotriosidase activity. We also compared plasma chitotriosidase activity in cystinotic knocked-out (nu2009=u200910) versus wild-type mice (nu2009=u200910).ResultsPlasma chitotriosidase activity in cystinotic patients (0–3880, median 163xa0nmol/ml/h) was significantly elevated compared to healthy controls (0–90, median 18xa0nmol/ml/h) and to CKD patients (0–321, median 52xa0nmol/ml/h), Pu2009<u20090.001 for both groups. Controls with decreased renal function had mild to moderate chitotriosidase elevations; however, their levels were significantly lower than in cystinotic patients with comparable degree of renal insufficiency. Chitotriosidase activity positively correlated with WBC cystine content for patients on cysteamine therapy (ru2009=u20090.8), Pu2009<u20090.001. In culture, human control macrophages engulfed cystine crystals and released TNF-α into culture supernatant in a crystal concentration dependent manner. Chitotriosidase activity was also significantly increased in macrophage supernatant and cell-lysate. Furthermore, chitotriosidase activity was significantly higher in cystinotic knocked-out than in the wild-type mice, Pu2009=u20090.003.ConclusionsThis study indicates that cystine crystals are potent activators of human macrophages and that chitotriosidase activity is a useful marker for this activation and a promising clinical biomarker and therapeutic monitor for nephropathic cystinosis.

WT-1 and NPHS2 mutation analysis in patients with non-familial steroid-resistant focal-segmental glomerulosclerosis.

BACKGROUNDnFamilial forms of steroid-resistant nephrotic syndrome with the histologic findings of focal-segmental glomerulosclerosis have frequently a genetic basis. For the non-familial forms this is still unresolved.nnnPATIENTS AND METHODSnTen children with non-familial steroid-resistant nephrotic syndrome along with focal-segmental glomerulosclerosis were tested for mutations in the WT-1 and NPHS2 genes.nnnRESULTSnIn 1 patient, a mutation in intron 9 of the WT-1 gene and in 1 patient a heterozygous NPHS2 mutation could be detected. Both abnormalities are important for the treatment modalities and prognosis.nnnCONCLUSIONnAdditional studies will have to provide a solid basis for the recommendation of mutation analysis in non-familial steroid-resistant focal-segmental glomerulosclerosis.

An Unusual Presentation of Denys-Drash Syndrome Due to Bigenic Disease

We report a case of Denys-Drash syndrome (DDS) in a 3-month-old girl presenting with bilateral renal cortical cysts mimicking polycystic kidney disease. Genetic analysis revealed a de novo heterozygous missense mutation c.1186G>A (p.Asp396Asn) in the WT1 gene, confirming the diagnosis of DDS. Because multiple renal cysts have never been reported in DDS, we explored several genes responsible for these renal manifestations, such as HNF-1β, PAX2, PKD1, and PKD2. Remarkably, we identified a heterozygous missense variant c.12439A>G (p.Lys4147Glu) in the PKD1 gene. The same variant was found in the patient’s mother, who had no renal cysts, and in the grandfather, who had several renal cysts. Mutation prediction programs classified the c.12439A>G variant as being “likely pathogenic.” We hypothesize that the severe cystic phenotype in the index patient could be due to the WT1 mutation, enhancing pathogenicity of the “hypomorph” PKD1 allele. A possible role for Wilms tumor suppressor 1 (WT1) in renal cyst development should be considered. From a conceptual point of view, this case shows that an unusual presentation of a known genetic syndrome might point to bigenic inheritance, with unexpected interference of mutated genes causing an uncommon clinical phenotype.