Study of the True Clinical Progression of Autosomal Dominant Alport Syndrome in a European Population.

BACKGROUND/AIMS: Autosomal dominant Alport syndrome represents 5% of all Alport syndrome cases. This entity presents a different clinical expression from the recessive inheritance pattern and the X chromosome-linked pattern, because it is mild and it shows a late onset, which in many cases even goes unnoticed. METHODS: We carried out a descriptive observational and retrospective clinical study on 19 patients from 5 families with a clinical diagnosis of autosomal dominant Alport Syndrome, and we analyzed the expression of the symptoms in the different families, comparing the results with what has been described in the literature. RESULTS: Renal involvement appeared at a young age, with a progression towards end-stage chronic kidney disease at a median age of 31 years (20.5-36.5). Hearing involvement also appeared in early stages, at a median age of 28.5 years (7.5-62.5). Also, we observed ocular lenticonus-like injuries, which until now have only been described in other inheritance patterns. CONCLUSIONS: Our results suggest that dominant patterns are accompanied by a severe clinical expression that can be superimposed to the recessive and X chromosome-linked patterns, contrary to what has been classically stated. The high phenotypic variability observed in the families lead to the fact that many cases go unnoticed and the severest cases are erroneously diagnosed as recessive, which means that the real prevalence of dominant forms is probably higher than the current 5%.

A new mutation in the COL4A3 gene responsible for autosomal dominant Alport syndrome, which only generates hearing loss in some carriers.

Bilateral sensorineural hearing loss is a characteristic feature of Alport syndrome, which is always linked to renal manifestations so they have a parallel evolution and prognosis, and deafness helps to identify the renal disease. We report a family that suffers an autosomal dominant Alport syndrome caused by a previously undescribed mutation in the COL4A3 gene, in which several members have hearing impairment as the only clinical manifestation, suggesting that in this family deafness can occur independent of renal disease. This mutation is also present in a patient with anterior lenticonus, an observation only found in families with recessive and sex-linked Alport disease.

COL4A4 gene study of a European population: description of new mutations causing autosomal dominant Alport syndrome.

BACKGROUND: Autosomal forms of Alport syndrome represent 20% of all patients (15% recessive and 5% dominant). They are caused by mutations in the COL4A3 and COL4A4 genes, which encode a-3 and a-4 collagen IV chains of the glomerular basement membrane, cochlea and eye. Thin basement membrane nephropathy may affect up to 1% of the population. The pattern of inheritance in the 40% of cases is the same as autosomal dominant Alport syndrome: heterozygous mutations in these genes. The aim of this study is to detect new pathogenic mutations in the COL4A4 gene in the patients previously diagnosed with autosomal Alport syndrome and thin basement membrane nephropathy in our hospital. METHODS: We conducted a clinical and genetic study in eleven patients belonging to six unrelated families with aforementioned clinical symptoms and a negative study of COL4A3 gene. The molecular study was made by conformation of sensitive gel electrophoresis (CSGE) and direct sequencing of the fragments that show an altered electrophoretic migration pattern. RESULTS: We found two pathogenic mutations, not yet described: IVS3 + 1G > C is a replacement of Guanine to Cytosine in position +1 of intron 3, in the splicing region, which leads to a pathogenic mutation. c.4267C > T; p.P1423S is a missense mutation, also considered pathogenic. We also found seven new polymorphisms. CONCLUSIONS: We describe two new pathogenic mutations, responsible for autosomal dominant Alport syndrome. The other families of the study were undiagnosed owing to problems in the method employed and the possibility of mutations in other genes, giving rise to other diseases with similar symptoms.

Encephalopathy caused by lanthanum carbonate.

Lanthanum carbonate is a nonaluminum, noncalcium phosphate-binding agent, which is widely used in patients with end-stage chronic kidney disease. Until now, no significant side-effects have been described for the clinical use of lanthanum carbonate, and there are no available clinical data regarding its tissue stores. Here we report the case of a 59-year-old patient who was admitted with confusional syndrome. The patient received 3750 mg of lanthanum carbonate daily. Examinations were carried out, and the etiology of the encephalopathy of the patient could not be singled out. The lanthanum carbonate levels in serum and cerebrospinal fluid were high, and the syndrome eased after the drug was removed. The results of our study confirm that, in our case, the lanthanum carbonate did cross the blood-brain barrier (BBB). Although lanthanum carbonate seems a safe drug with minimal absorption, this work reveals the problem derived from the increase of serum levels of lanthanum carbonate, and the possibility that it may cross the BBB. Further research is required on the possible pathologies that increase serum levels of lanthanum carbonate, as well as the risks and side-effects derived from its absorption.