(Of note, Autosomal Dominant RP Type 11 (PRPF-31) can be inherited as a genotype only, because of incomplete penetrance, thus coded for in the DNA but, does not manifest the disease as a phenotype.) In 1989, a mutation of the gene for rhodopsin, a pigment that plays an essential part in the visual transduction cascade enabling vision in low-light conditions, was identified. The rhodopsin gene encodes a principal protein of photoreceptor outer segments. Mutations in this gene most commonly presents as missense mutations or misfolding of the rhodopsin protein, and most frequently follow autosomal dominant inheritance patterns. Since the discovery of the rhodopsin gene, more than 100 RHO mutations have been identified, accounting for 15% of all types of retinal degeneration, and approximately 25% of autosomal dominant forms of RP.Over 100 mutations have been reported to date in the opsin gene associated with the RP since the Pro23His mutation in the intradiscal domain of the protein was first reported in 1990. These mutations are found throughout the opsin gene and are distributed along the three domains of the protein (the intradiscal, transmembrane, and cytoplasmic domains). One of the main biochemical causes of RP in the case of rhodopsin mutations is protein misfolding, and the disruption of molecular chaperones. It was found that the mutation of codon 23 in the rhodopsin gene, in which proline is changed to histidine, accounts for the largest fraction of rhodopsin mutations in the United States.
Neurogenic diabetes insipidus can be a failure of production at the hypothalamus, or a failure of release at the pituitary. Genetic
The most rare form of central DI is familial neurogenic diabetes insipidus. This form of DI is due to an inherited mutation of the arginine vasopressin-neurophysin II (AVP-NPII) gene, inherited in an autosomal dominant manner. At one point, only 45 families worldwide were known to possess this genetic trait. It is now more widely recognized, although the precise number of people affected with this form of DI is unknown at the present time.There is also an X-linked familial form.Wolfram Syndrome (also called DIDMOAD) is characterised by DI, diabetes mellitus, sensorineural deafness, and optic atrophy. Diagnosis
In many respects, the diagnosis of central diabetes insipidus begins as a diagnosis of exclusion. Specifically, other more common causes of polyuria and polydipsia are ruled out. Common rule outs include: diabetes mellitus, chronic kidney disease, hypokalemia, hypercalcemia, and psychogenic polydipsia. Once these conditions have been ruled out a water deprivation test is employed to confirm the diagnosis of CDI. Treatment
The disorder is treated with vasopressin analogs such as desmopressin. Nonetheless, many times desmopressin alone is not enough to bring under control all the symptoms, and another intervention must be implemented. See also
Fluid deprivation test

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