Lower urinary tract obstruction by posterior urethral valves (PUV) is an important cause of congenital renal failure in male infants. Though population-based studies point to a role of genetic factors in the etiology of PUV, no clear evidence for a specific gene defect for PUV has been observed so far. Here we present a consanguineous family with four male descendants affected by PUV and a healthy girl, suggestive of autosomal recessive inheritance. One boy presented with prune-belly syndrome (PBS) in addition to PUV. Using a DNA chip-based genome-wide linkage analysis, we identified a region of homozygosity for the affected boys in an interval of 35 cM on chromosome 1q41-44 with a maximum multipoint LOD score of Z(max) = 3.134 at theta = 0 for single nucleotide polymorphisms (SNPs) rs158724-rs720163. By applying a second genetic model based on the assumption of a male-limited phenotype and the girl being carrier of the genetic defect without expressing the phenotype, a second alternative locus of 9 cM on chromosome 11p11 was identified with a LOD score of Z(max) = 3.61 at theta = 0. Equal significance for both loci with a LOD score of Z(max) = 3.01 at theta = 0 was obtained after the affection status of the female descendant was set "unknown". We suppose that most probably, only one of the two identified loci harbours the disease-causing gene. As the interpretation of the girl's status remains uncertain, we are not able to exclude one of the two loci. Analyses of additional informative families will be important to exclude one of the two loci and to restrict the critical interval.

Reduced bone mass is a common complication of renal transplantation in adults but only few data are present for pediatric transplant patients. Bone mineral status of pediatric renal transplant patients ages ranging from 7.5 to 17.6 years (mean age 14.9 +/- 2.3) who were at least 6 months postrenal transplantation was examined. Bone mineral density (BMD) of lumbar vertebrea and femoral neck was determined by dual energy X-ray absorptiometry (DEXA) and z-scores according to age, puberty, height and bone age were compared to sex and ethnic specific reference data. z-scores were calculated for both areal and volumetric bone density. BMD L1-4 z-scores were more than 2 SD below the mean according to chronological age in 12 patients (63%), pubertal status in six patients (31.5%), bone age in five patients (26.3%) and height in five patients (26.3%). The BMD femoral neck z-scores were more than 2 SD below the mean according to age in 10 patients (55.5%), puberty in five patients (27.7%), bone age in three (16.6%) patients and height in five (26.3%) patients. Correction of the vertebrae and femoral neck for bone size yielded osteoporotic values for seven patients (36.8%) for lumbar BMD and for four patients (22%) for femoral neck BMD. The use of aBMD in growth-retarded children has some restrictions in determining z-scores. Deficits in spinal bone density still persisted after correcting for height, puberty, bone age and volume. In renal transplant patients who have short stature it is reasonable to give values corrected for height, puberty, bone age and bone size and interpret each of these values for each patient.