Causes
The vast majority of cases are thought to be due to spontaneous genetic mutations. It can be associated with mutations affecting the cohesin complex.As of 2018, it was confirmed that 500 genetic mutations have been associated with the condition; occurring on 7 different genes. In around 30% of cases of CdLS the genetic cause remains undiscovered. The wide variation in phenotype is attributed to a high degree of somatic mosaicism in CdLS as well as the different genes and type of mutations. For this reason people with CdLS can have very different appearance,  abilities,  and associated health issues. The latter two genes seem to correlate with a milder form of the syndrome.In 2004, researchers at the Childrens Hospital of Philadelphia (United States) and the University of Newcastle upon Tyne (England) identified a gene (NIPBL) on chromosome 5 that causes CdLS when it is mutated. Since then, additional genes have been found (SMC1A, SMC3 and HDAC8, RAD21) that cause CdLS when changed. In July 2012, the fourth "CdLS gene"—HDAC8—was announced. HDAC8 is an X-linked gene, meaning it is located on the X chromosome. Individuals with CdLS who have the gene change in HDAC8 make up just a small portion of all people with CdLS. Evidence of a linkage at chromosome 3q26.3 is mixed.Genetic alterations associated with CdLS have been identified in genes NIPBL, SMC1A and SMC3 as well as the more recently identified genes RAD21 and HDAC8. All of these genetic alterations occurring in CdLS patients affect proteins that function in the cohesin pathway.
However, when plasma blood volume is low and ADH is released the aquaporins that are opened are also permeable to urea. This allows urea to leave the collecting duct into the medulla, creating a hyperosmotic solution that "attracts" water. Urea can then re-enter the nephron and be excreted or recycled again depending on whether ADH is still present or not. The single effect describes the fact that the ascending thick limb of the loop of Henle is not permeable to water but is permeable to sodium chloride. This allows for a countercurrent exchange system whereby the medulla becomes increasingly concentrated, but at the same time setting up an osmotic gradient for water to follow should the aquaporins of the collecting duct be opened by ADH. Blood pressure
Although the kidney cannot directly sense blood, long-term regulation of blood pressure predominantly depends upon the kidney. This primarily occurs through maintenance of the extracellular fluid compartment, the size of which depends on the plasma sodium concentration. Renin is the first in a series of important chemical messengers that make up the renin–angiotensin system. Changes in renin ultimately alter the output of this system, principally the hormones angiotensin II and aldosterone. Each hormone acts via multiple mechanisms, but both increase the kidneys absorption of sodium chloride, thereby expanding the extracellular fluid compartment and raising blood pressure. When renin levels are elevated, the concentrations of angiotensin II and aldosterone increase, leading to increased sodium chloride reabsorption, expansion of the extracellular fluid compartment, and an increase in blood pressure.