Mistargeting of peroxisomal EHHADH and inherited renal Fanconi's syndrome.

BACKGROUND: In renal Fanconi's syndrome, dysfunction in proximal tubular cells leads to renal losses of water, electrolytes, and low-molecular-weight nutrients. For most types of isolated Fanconi's syndrome, the genetic cause and underlying defect remain unknown. METHODS: We clinically and genetically characterized members of a five-generation black family with isolated autosomal dominant Fanconi's syndrome. We performed genomewide linkage analysis, gene sequencing, biochemical and cell-biologic investigations of renal proximal tubular cells, studies in knockout mice, and functional evaluations of mitochondria. Urine was studied with the use of proton nuclear magnetic resonance ((1)H-NMR) spectroscopy. RESULTS: We linked the phenotype of this family's Fanconi's syndrome to a single locus on chromosome 3q27, where a heterozygous missense mutation in EHHADH segregated with the disease. The p.E3K mutation created a new mitochondrial targeting motif in the N-terminal portion of EHHADH, an enzyme that is involved in peroxisomal oxidation of fatty acids and is expressed in the proximal tubule. Immunocytofluorescence studies showed mistargeting of the mutant EHHADH to mitochondria. Studies of proximal tubular cells revealed impaired mitochondrial oxidative phosphorylation and defects in the transport of fluids and a glucose analogue across the epithelium. (1)H-NMR spectroscopy showed elevated levels of mitochondrial metabolites in urine from affected family members. Ehhadh knockout mice showed no abnormalities in renal tubular cells, a finding that indicates a dominant negative nature of the mutation rather than haploinsufficiency. CONCLUSIONS: Mistargeting of peroxisomal EHHADH disrupts mitochondrial metabolism and leads to renal Fanconi's syndrome; this indicates a central role of mitochondria in proximal tubular function. The dominant negative effect of the mistargeted protein adds to the spectrum of monogenic mechanisms of Fanconi's syndrome. (Funded by the European Commission Seventh Framework Programme and others.).

Childhood scleromyositis with a negative PM/Scl antibody.

Overlap syndromes, such as scleromyositis, antisynthetase syndrome and mixed connective tissue disease, consist of a blend of clinical features involved in two separate autoimmune disorders. Scleromyositis, the most common overlap syndrome, is usually observed in adults, and has rarely been documented in childhood. Here, the case of a 10-year-old African American female with scleromyositis is reported. This disease has features of both dermatomyositis and systemic scleroderma. Her disease process began with signs and symptoms of dermatomyositis and slowly changed clinically to features of systemic scleroderma. This patient had a positive ANA with a nucleolar pattern and a negative anti-PM/Scl antibody, an antibody which has been used as a prognostic and diagnostic marker of scleromyositis.

Changing epidemiology of acute post-streptococcal glomerulonephritis in Northeast Florida: a comparative study.

The objective of this study was to review the epidemiological patterns of acute post-streptococcal glomerulonephritis (APSGN) in a pediatric population. We compared incidence, pathogenesis, clinical presentation and outcomes in two APSGN pediatric patient cohorts in northeastern Florida. Retrospective medical records were reviewed of children who were admitted to our institution with a diagnosis of APSGN. Patients admitted between 1999 and 2006 (recent cohort) were compared with a previously reported cohort of patients admitted between 1957 and 1973 (earlier cohort). The recent cohort comprised 45 children with APSGN of whom 87% were male and 13% were female; the median age was 7 years, and there was an average incidence of 6.4 patients per year. The earlier cohort comprised 153 children with APSGN of whom 62% were male and 38% were female; the median age 4.25 years, and there was an average incidence of 10.9 patients per year. The recent cohort was predominantly White-American (62%) and the earlier cohort predominately African American (87%). In the recent cohort, 64% of patients had antecedent pharyngitis, and in the earlier cohort, 66% of patients had antecedent pyoderma. In the recent cohort, 11% of APSGN cases occurred between August to October, and in the earlier cohort, 50% occurred during these months. In the recent cohort, symptoms of APSGN at presentation were milder and all cases recovered, but in the earlier cohort two deaths (1.3% mortality) were reported. In conclusion, there has been a decline in the incidence and severity of APSGN at our institute in recent decades. Pharyngitis has replaced impetigo as the predominant cause of APSGN. The etiological agent for impetigo has changed over the last decade, which has impacted the incidence, racial distribution, seasonal variation and severity of APSGN.

Nephrotoxicity in a child with perinatal HIV on tenofovir, didanosine and lopinavir/ritonavir.

Tenofovir-related tubule damage characterized by Fanconi syndrome, renal insufficiency and nephrogenic diabetes insipidus has been reported in the adult HIV-infected population. To our knowledge there has been no reported case of such complications in the pediatric population. We report the case of a 12-year-old perinatally HIV-infected African-American girl who developed nephrogenic diabetes insipidus, renal insufficiency and Fanconi-like syndrome while taking tenofovir (Viread) in combination with lopinavir-ritonavir (Kaletra) and didanosine (Videx).

Hypertension and the vanishing kidney.

The diagnostic role of retrograde pyelography in children with secondary hypertension has never been discussed in the literature. We report a child with severe hypertension, who apparently has a normal renin level and a solitary kidney by renal sonography and renal scan. Retrograde pyelography was able to identify the scarred renal mass. To our knowledge this is the first report to discuss the role of retrograde pyelography in a child with a solitary kidney and severe hypertension.

Minimal change nephrotic syndrome with Guillain-Barré syndrome.

A 17-year-old white male with a diagnosis of Guillain-Barré syndrome (GBS) developed severe proteinuria and edema 5 days later. Renal biopsy confirmed minimal change nephrotic syndrome (MCNS). To our knowledge this is the first report of such an association between ex novo MCNS and GBS in a pediatric patient. The NS responded to steroid therapy. The pertinent literature is reviewed.