Linkage analysis confirms heterogeneity of hereditary gingival fibromatosis.

OBJECTIVES: Hereditary Gingival Fibromatosis (HGF) is a rare benign fibrous lesion of the gingival tissues presumably caused by single gene defects. The aim of this study was to identify the genetic defect leading to HGF in an extended pedigree. MATERIALS AND METHODS: We report the clinical features and genetic analysis of a family affected by HGF. A total of 17 subjects were assessed clinically and had blood samples taken for DNA extraction. Multipoint parametric linkage analysis was performed to identify the possible chromosomal location responsible for HGF in this family. RESULTS: Presence of severe HGF associated with tooth impaction was confirmed for seven members of this three-generation family. Linkage analysis revealed that loci on chromosomes 7, 10, 13, 15, 16, 17, 19 and 20 were linked to this trait. Previously found mutations in the SOS1 and GINGF loci were therefore excluded by this analysis. CONCLUSIONS: This study brings further evidence for genetic heterogeneity of HGF and points towards the existence of different, not-yet-identified genes linked to this condition.

A common variant of the latrophilin 3 gene, LPHN3, confers susceptibility to ADHD and predicts effectiveness of stimulant medication.

Attention-Deficit/Hyperactivity Disorder (ADHD) has a very high heritability (0.8), suggesting that about 80% of phenotypic variance is due to genetic factors. We used the integration of statistical and functional approaches to discover a novel gene that contributes to ADHD. For our statistical approach, we started with a linkage study based on large multigenerational families in a population isolate, followed by fine mapping of targeted regions using a family-based design. Family- and population-based association studies in five samples from disparate regions of the world were used for replication. Brain imaging studies were performed to evaluate gene function. The linkage study discovered a genome region harbored in the Latrophilin 3 gene (LPHN3). In the world-wide samples (total n=6360, with 2627 ADHD cases and 2531 controls) statistical association of LPHN3 and ADHD was confirmed. Functional studies revealed that LPHN3 variants are expressed in key brain regions related to attention and activity, affect metabolism in neural circuits implicated in ADHD, and are associated with response to stimulant medication. Linkage and replicated association of ADHD with a novel non-candidate gene (LPHN3) provide new insights into the genetics, neurobiology, and treatment of ADHD.

Antenatal Bartter's syndrome: why is this not a lethal condition?

There are four themes in this teaching exercise for Professor McCance. The first challenge was to explain how a premature infant with Bartter's syndrome could survive despite having such a severe degree of renal salt wasting. Second, the medical team wanted to know why there was such a dramatic decrease in the natriuresis in response to therapy, despite the presence of a permanent molecular defect that affected the loop of Henle. Third, Professor McCance was asked why this patient seemed to have a second rare disease, AQP2 deficiency type of nephrogenic diabetes insipidus. The fourth challenge was to develop a diagnostic test to help the parents of this baby titrate the dose of indomethacin to ensure an effective dose while minimizing the likelihood of developing nephrotoxicity. The missing links in this interesting story emerge during a discussion between the medical team and its mentor.

Aminoacidurias: Clinical and molecular aspects.

Inherited aminoacidurias are caused by defective amino-acid transport through renal (reabsorption) and in many cases also small intestinal epithelia (absorption). Recently, many of the genes causing this abnormal transport have been molecularly identified. In this review, we summarize the latest findings in the clinical and molecular aspects concerning the principal aminoacidurias, cystinuria, lysinuric protein intolerance, Hartnup disorder, iminoglycinuria, and dicarboxylic aminoaciduria. Signs, symptoms, diagnosis, treatment, causative or candidate genes, functional characterization of the encoded transporters, and animal models are discussed.

Genotypic heterogeneity and clinical phenotype in triple A syndrome: a review of the NIH experience 2000-2005.

Triple A syndrome (AAAS, OMIM#231550) is an autosomal recessive condition characterized by adrenal insufficiency, achalasia, alacrima, neurodegeneration and autonomic dysfunction. Mutations in the AAAS gene on chromosome 12q13 have been reported in several subjects with AAAS. Over the last 5 years, we have evaluated six subjects with the clinical diagnosis of AAAS. Three subjects had mutations in the AAAS gene-- including one novel mutation (IVS8+1 G>A)-- and a broad spectrum of clinical presentations. However, three subjects with classic AAAS did not have mutations in the AAAS gene on both alleles. This finding supports the notion of genetic heterogeneity for this disorder, although other genetic mechanisms cannot be excluded.

CTNS mutations in African American patients with cystinosis.

Cystinosis, an autosomal recessive lysosomal storage disorder, is rarely diagnosed in African Americans. The disease results from mutations in the gene CTNS; at least 55 such mutations have been reported. By far the most common is a 57,257-bp deletion of Northern European origin encompassing most of the CTNS gene. We performed mutation analysis on DNA from four African American patients with cystinosis. In one individual with classical, nephropathic cystinosis, we identified a new molecular defect, i.e., a homozygous GT-->CC substitution at the +5 position of IVS 5 of CTNS (IVS 5+5 GT-->CC). The out-of-frame splicing of exon 5 creates a null allele consistent with the patient's severe phenotype. Two patients were heterozygous and one homozygous for the common 57-kb deletion allele, reflecting the admixture of African and Northern European gene pools in North America. The two African Americans heterozygous for the 57-kb deletion were also hemizygous for a 928G-->A change, associated with ocular or nonnephropathic cystinosis. These two individuals are the only known African Americans with ocular cystinosis. We conclude that the diagnosis of cystinosis should be entertained in African Americans with symptoms of the disease, and that mutation analysis for the 57-kb deletion should be considered in this group of patients.

Type III 3-methylglutaconic aciduria (optic atrophy plus syndrome, or Costeff optic atrophy syndrome): identification of the OPA3 gene and its founder mutation in Iraqi Jews.

Type III 3-methylglutaconic aciduria (MGA) (MIM 258501) is a neuro-ophthalmologic syndrome that consists of early-onset bilateral optic atrophy and later-onset spasticity, extrapyramidal dysfunction, and cognitive deficit. Urinary excretion of 3-methylglutaconic acid and of 3-methylglutaric acid is increased. The disorder has been reported in approximately 40 patients of Iraqi Jewish origin, allowing the mapping of the disease to chromosome 19q13.2-q13.3, by linkage analysis. To isolate the causative gene, OPA3, we sequenced four genes within the critical interval and identified, in the intronic sequence of a gene corresponding to cDNA clone FLJ22187, a point mutation that segregated with the type III MGA phenotype. The FLJ22187-cDNA clone, which we identified as the OPA3 gene, consists of two exons and encodes a peptide of 179 amino acid residues. Northern blot analysis revealed a primary transcript of approximately 5.0 kb that was ubiquitously expressed, most prominently in skeletal muscle and kidney. Within the brain, the cerebral cortex, the medulla, the cerebellum, and the frontal lobe, compared to other parts of the brain, had slightly increased expression. The intronic G-->C mutation abolished mRNA expression in fibroblasts from affected patients and was detected in 8 of 85 anonymous Israeli individuals of Iraqi Jewish origin. Milder mutations in OPA3 should be sought in patients with optic atrophy with later onset, even in the absence of additional neurological abnormalities.

Familial hypomagnesemia-hypercalciuria in 2 siblings.

Familial hypomagnesemia-hypercalciuria with nephrocalcinosis and renal insufficiency in childhood is a rarely described disease. Two siblings of consanguineous Tunesian parents (first cousins), a 2-year-old boy and a 4-year-old girl presented with renal insufficiency and severe bilateral nephrocalcinosis. Both were found to have decreased serum and intracellular magnesium concentrations, increased urinary excretion of magnesium and calcium, mild glomerular and severe tubular proteinuria and low citrate excretion in urine. Pathological biochemical findings and the severity of nephrocalcinosis of the boy compared to findings of the sister were strongly marked, Histology of the boy's kidney showed severe medullary nephrocalcinosis, tubular atrophy, focal lymphoplasmacellulary infiltration, focal cortical fibrosis, immature glomerula, segmental and global glomerulosclerosis. Subsequent mutation analysis revealed a homozygous frameshift mutation in the gene paracellin-1 in both affected individuals. Therapy consisted of sodium bicarbonate, cholecalciferol, calcitriol, hydrochlorothiazide, citrate salts and oral magnesium administration. Hypercalciuria decreased in both children by therapy with thiazide diuretics, but hypomagnesemia was unresponsive to magnesium administration. After a 32-month follow-up the boy commenced hemodialysis at the age of 5 years, whereas his sister showed no decline in renal function.

[Arthrogryposis, renal tubular dysfunction, cholestasis (ARC) syndrome: case report and review of the literature]. / Arthrogryposis, renale tubuläre Dysfunktion, Cholestase (ARC)-Syndrom: Fallbeschreibung und Literaturübersicht.

The ARC-syndrome is a rare disease with the obligatory symptoms arthrogryposis, renal tubular dysfunction and cholestasis. Optional further symptoms like ichthyosis, diarrhea, central nervous system defects and recurrent infections have been reported. The ARC-syndrome was first reported by Lutz-Richner and Landolt in 1973. The pathophysiology is still unknown, an autosomal recessive inheritance is postulated. Patients rarely exceed an age of six month. We report a boy of consanguineous Turkish parents who suffered from congenital deformities of the lower extremities, a metabolic acidosis and failure to thrive. In the sequel he developed a renal Fanconi syndrome and cholestasis. Histology of liver and muscle biopsy specimen showed the typical findings of the disease with giant cell hepatitis and neurogenous muscle atrophy. His condition could be stabilized and he increased in weight by substituting fluid, electrolytes, buffer and parenteral nutrition. Total enteral nutrition of the 280 ml/kg/d he required failed even by nasogastric tube and percutaneous endoscopic gastrostomy. Additional fluid substitution by central venous catheter remained necessary. At the age of 7 month he died.

Small-cell carcinoma of the ovary of the hypercalcemic type in an 8-year-old girl.

Tumors of the ovary in girls represent about 80% of pediatric genital tumors; approximately 30% of these tumors are malignant. The risk of malignancy increases with decreasing age. The most frequent finding is a teratoma; other tumors are rare. Small-cell carcinoma (SCCO) of the ovary is extremely rare, occurring mostly in young women. We present an 8-year-old girl with a SCCO of the hypercalcemic type. The findings and treatment are discussed with emphasis on the poor prognosis in these patients, even in stage 1 disease. The current literature is reviewed.

Renal involvement in children with malignancies.

Renal complications in children with malignancies primarily arise from renal parenchymal tumors, "tumor lysis syndrome," and malignant infiltration or obstruction of the urinary tract. Therapy-associated renal side effects may develop following surgical and cytostatic treatment or be induced by radiotherapy. Clinically, both acute renal failure, for example following cisplatin, or chronic dysfunction, following ifosfamide and resulting in growth failure, are observed. Frequencies of renal impairment in these patients are, however, not well established, but terminal renal failure is a rare event: pediatric malignancies account for only 0.9% of patients on renal replacement therapy; the majority of these patients had been treated for a bilateral nephroblastoma. Since potentially serious long-term renal sequelae may evolve following both single measures and additive nephrotoxic effects, long-term monitoring of growth, blood pressure, and renal function is mandatory for a great proportion of former pediatric oncology patients. Future research should prospectively address frequencies of long-term renal impairment in these patients and should establish the prognosis of renal dysfunction. Only these data will ultimately allow risk-adopted use of potentially nephrotoxic treatment modalities and adequate counselling of patients.

Development of ifosfamide-induced nephrotoxicity: prospective follow-up in 75 patients.

PURPOSE: This study was performed to describe prospectively the development and prognosis of severe ifosfamide-induced nephrotoxicity and to define the period of recommended renal follow-up after ifosfamide chemotherapy. PATIENTS AND METHODS: Renal function was followed in 75 patients after cessation of chemotherapy starting within the first year off therapy; median follow-up time was 31 months. The glomerular filtration rate was estimated by using the Schwartz formula. Proximal tubular transport capacities were evaluated for amino acids, phosphate, sodium, and glucose. In addition, serum bicarbonate level and alkaline phosphatase were measured. RESULTS: Five patients developed renal Fanconi syndrome during follow-up, and another seven patients developed a generalized subclinical tubulopathy. The latter condition always preceded Fanconi syndrome. Severe impairment of amino acid and phosphate reabsorption was seen in 28% and 17.3% of patients, respectively. Reductions in amino acid reabsorption preceded impairment of phosphate reabsorption. In patients with early impairment of phosphate reabsorption, renal prognosis was poor, whereas normal or only mildly impaired amino acid handling virtually excluded progressive tubular damage. CONCLUSIONS: Ifosfamide-induced renal tubular damage is a potentially progressive disease. Along with measurement of phosphate reabsorption, additional assessment of tubular amino acid handling is suggested, because it allows early discrimination of poor from favorable renal outcomes.