The genetics of enuresis: a review

PURPOSE

Formal studies of the genetics of enuresis have been performed since the 1930s and molecular genetics since 1995, both highlighting the importance of hereditary factors in the etiology of nocturnal enuresis. We summarize the current state of knowledge with respect to the genetics of nocturnal enuresis and its genotype-phenotype interactions.

MATERIALS AND METHODS

A comprehensive review of the published data available on the genetic basis of enuresis was performed.

RESULTS

Genetic factors are the most important in the etiology of nocturnal enuresis but somatic and psychosocial environmental factors have a major modulatory effect. Most commonly, nocturnal enuresis is inherited via an autosomal dominant mode of transmission with high penetrance (90%). However, a third of all cases are sporadic, and the difference between sporadic and familial forms is not known. Four gene loci associated with nocturnal enuresis have been identified but the existence of others is presumed (locus heterogeneity). All likely candidate genes have been excluded so far. There is no specific association among the different loci, type of wetting and other aspects of the phenotype. All subtypes of nocturnal enuresis (primary, secondary, combined day/night wetting) are susceptible to comparable genetic influences. Certain syndromes of day wetting follow their own genetic mechanisms but this association with the genetics of nocturnal enuresis is not known.

CONCLUSIONS

Nocturnal enuresis is a common, genetic and heterogeneous disorder. The associations between genotype and phenotype are complex and are susceptible to environmental influences. Therefore, exact assessment of the clinical phenotype and identification of intermediary phenotypes or traits are needed. Future research will focus on the identification of genes, gene products and their interaction with environmental factors.

Long-term home studies of water balance in patients with nocturnal enuresis

A 2-week, home-based study was conducted on 75 children with nocturnal enuresis to monitor the frequency of enuretic episodes and the volume of nocturnal urine production. The objectives of the study were to correlate nocturnal urine production to the occurrence of nocturnal enuresis and response to desmopressin (Minirin, DDAVP) treatment. Furthermore, patient compliance was evaluated. Enuresis episodes and nocturnal urine production was recorded every night during two base-line weeks without treatment and during 2 weeks with 20-40 micrograms desmopressin at bedtime. During both periods fluid intake and micturition volumes were recorded for 2 days. Desmopressin response was defined as > 50% reduction in wet nights during treatment. It was found that patient compliance was acceptable in most patients. Regarding urine output it was found that base-line nocturnal urine production was significantly higher during nights when enuresis occurred than during "dry" nights and significantly higher in desmopressin responders compared with desmopressin non-responders. During treatment with desmopressin, nocturnal urine production in desmopressin responders decreased to levels similar to those of non-responders. The results confirm inpatient circadian studies of urine output and emphasise the importance of nocturnal polyuria in patients with monosymptomatic enuresis. The response to desmopressin was found to correlate with the occurrence of nocturnal polyuria. Home studies were considered to be a useful tool in the characterisation of patients with nocturnal enuresis.

Peripheral neuropathy induced by 2',3'-dideoxycytidine. A rabbit model of 2',3'-dideoxycytidine neurotoxicity

The nucleoside analog 2',3'-dideoxycytidine (ddC) is a potent inhibitor of the reverse transcriptase of human immunodeficiency virus and a DNA chain terminator. In clinical trials in patients with acquired immunodeficiency syndrome, ddC treatment has been associated with a dose-limiting and dose-dependent, painful, sensorimotor peripheral neuropathy. In search of an animal model for ddC-induced neurotoxicity we studied 36 New Zealand White rabbits (3 males/3 females/group) given 0, 10, 50, 100, 150, or 250 mg/kg/day of ddC, by oral intubation, for 13 or 18 weeks. Rabbits in the 150 and 250 mg/kg/day groups were sacrificed at 13 weeks because of hematopoietic toxicity. After 16 weeks, rabbits in the 50 and 100 mg/kg/day groups showed hindlimb paresis and/or gait abnormalities. Nerve conduction velocities and amplitudes in the 100 mg/kg/day rabbits were reduced by 30 to 50%. The most prominent pathologic changes in peripheral nerve and ventral roots of ddC-treated rabbits were (a) myelin splitting and intramyelinic edema, (b) demyelination and remyelination of axons, and (c) axonal loss. Treatment-related histologic lesions were not observed in spinal cord, brain, or retina. The pathology in these ddC-treated rabbits is consistent with a peripheral myelinopathy and axonopathy. This represents the first clinical, electrophysiologic, and pathologic description of an animal model of a peripheral neuropathy induced by a nucleoside analog.

Distal axonopathy associated with chronic gluten enteropathy: a treatable disorder

Our experience with one patient and literature review reveals that patients with chronic gluten enteropathy and severe steatorrhea may develop a generalized peripheral neuropathy of the distal axonopathy type. Vitamin levels are usually normal, and the neuropathy appears to respond to gluten restriction.

A comparative study of 'Op-site' and 'Nobecutan gauze' dressings for central venous line care

A comparative study of 'Op-site' and 'Nobecutan-gauze' dressings for central venous lines was performed. Seventy-seven long antebrachial and 68 infraclavicular subclavian catheters were studied. A statistically significant reduction in the incidence of positive cultures from the catheter tip and from the skin puncture site was found with the 'Nobecutan-gauze' dressing. No difference in the incidence of catheter-related septicaemia was found. The theoretical advantage of being able to observe signs of inflammation when 'Op-site' was used did not reduce the incidence of local infection at the skin puncture site. In conclusion we found that a 'Nobecutan-gauze' dressing was a satisfactory alternative to an 'Op-site' dressing.

Sensory neuropathy from pyridoxine abuse. A new megavitamin syndrome

We describe seven adults who had ataxia and severe sensory-nervous-system dysfunction after daily high-level pyridoxine (vitamin B6) consumption. Four were severely disabled; all improved after withdrawal. Weakness was not a feature of this condition, and the central nervous system was clinically spared. Although consumption of large doses of pyridoxine has gained wide public acceptance, this report indicates that it can cause sensory neuropathy or neuronopathy syndromes and that safe guidelines should be established for the use of this widely abused vitamin.

Adrenoleukodystrophy: elevated C26 fatty acid in cultured skin fibroblasts

Because postmortem brain and adrenal tissue from patients with adrenoleukodystrophy (ALD) or adrenomyeloneuropathy (AMN) have been shown to contain abnormally large amounts of very long chain fatty acids (C24 through C30), we searched for such an abnormality in cultured skin fibroblasts. Total lipid extracts of cultured fibroblasts were hydrolyzed, their fatty acid composition was determined by gas-liquid chromatography, and the ratio of C26 to C22 fatty acids was calculated. In 29 control cell lines this ratio was 0.064 +/- 0.019. In 5 patients with autopsy-proved ALD the ratio was 0.778 +/- 0.139; in 6 patients with clinical features typical of ALD it was 0.764 +/- 0.092; in 2 patients with autopsy-proved AMN, 0.890 +/- 0.02; and in 2 patients with clinical features typical of AMN, 0.560 +/- 0.079. Abnormal ratios were observed in 4 of 5 ALD heterozygotes. In 3 patients in whom the diagnosis of ALD was suspected, an abnormal ratio (0.860) was observed in 1 and normal ratios (0.06 and 0.074) in the 2 others.

Adrenomyeloneuropathy: a probable variant of adrenoleukodystrophy. I. Clinical and endocrinologic aspects

We have studied four unrelated males with a heritable disorder that we term adrenomyeloneuropathy; limited clinical information is available on a fifth case. All had adrenal insufficiency beginning in childhood and developed progressive spastic paraparesis in the third decade. Hypogonadism of variable severity was present in all four cases appropriately examined. Neurologic features included peripheral neuropathy, impotence, and sphincter disturbances. Late manifestations were cerebellar dysfunction in one case and dementia and hemiparesis in another. A family history of adrenal disease or spastic paraparesis was present in two cases and absent in one; in the other two, no family history was available. Although males are predominantly affected, the mode of inheritance is uncertain. Adrenomyeloneuropathy probably represents a clinically and genetically distinct variant of childhood adrenoleukodystrophy.