Thursday, March 5, 2009

Uremic Pruritis

Recent review in the latest issue of Nature Clinical Practice Nephrology entitled "Skin problems in chronic kidney disease." They tackle the usual suspects (calciphylaxis, nephrogenic systemic fibrosis) as well as some lesser-known dermatologic conditions which appear with a higher prevalence in dialysis populations, such as porphyria cutanea tarda and acquired perforating dermatosis.

Uremic pruritis is less common today than it once was--presumably because underdialysis is less common. However, it is still present in varying degrees to up to 52% of adult dialysis patients according to the DOPPS study. Itching tends to be worse at night but also can occur with dialysis. The pathophysiology is poorly understood and a number of potential mechanisms have been proposed to acccount for uremic pruritis. One theory posits that pruritis is part of an immune-mediate systemic inflammatory illness. In support of this idea, several therapies known effective in treating uremic pruritis--such as UV therapy, thalidomide, or topical tacrolimus--are all known to target the immune system. Furthermore, individuals with uremic pruritis are more likely to have elevated levels of non-specific markers of inflammation such as CRP. Another hypothesis suggests that alterations in the ratios of endogenous opioids that tend to occur in dialysis patients mediates an abnormal activaton of dermal opioid receptors; this provides the rationale for using drugs such as naltrexone for treatment of uremic pruritis. Other factors suggested to play a role in uremic pruritis include secondary hyperparathyroidism, abnormal histamine release, and dry skin.

Therapy for uremic pruritis should include ensuring that patients are receiving adequate dialysis, potentially using high-flux dialyzers, topical treatments such as capsaicin, tacrolimus, or simple emollients, UV therapy, gabapentin, or medications which target the opioid receptor.

1 comment:

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