IntroductionChronic itch associated with systemic diseases continues to be one of the most bothersome dermatological symptoms accompanying end-stage renal disease (ESRD), chronic liver diseases, and lymphoma. The International Forum for the Study of Itch has recently issued a consensus paper on different types of chronic pruritus, including pruritus in systemic diseases that can present with or without secondary skin changes.1Various types of itch have been described based on the origin of the itch, which could be skin-related, neuropathic, systemic, or psychogenic.2 At any given time patients with these systemic diseases may have more than one origin, for example, patients with end-stage renal disease (ESRD) could have neuropathic itch due to nerve fibers damage, as well as itch associated with skin inflammation such as perforating folliculitis. Itch adversely affects quality of life of patients, leading to sleep deprivation and depression that further augment itch. Chronic itch associated with systemic diseases range from mild to intractable, which is defined as a chronic itch state in which the cause cannot be removed or treated, and no relief or cure has been found in the generally accepted course of medical practice.3 In the last decade, there are significant advances in our understanding of specific itch neuronal pathways, mediators and relevant receptors, opening the field for development of new antipruritic strategies. The purpose of this review is to highlight the new findings related to the pathophysiological mechanisms and the treatment of itch associated with the most common systemic diseases including ESRD, chronic liver disease and lymphoma.
EpidemiologyA recent study estimated that approximately one in five dermatology outpatients with generalized pruritus with no obvious dermatologic cause may have an underlying systemic cause.4 This result underscores the significance of ruling out potential underlying systemic diseases when seeing a patient with generalized itch.Chronic itch remains as one of the most common symptoms in patients with ESRD, particularly in hemodialysis (HD) patients. Although the prevalence of itch has decreased in the last 30 years, itch remains a major problem in ESRD. The overall prevalence of pruritus in a recent study in US was 57%.5 The largest study so far analyzed data from 18,801 HD (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004) and indicated that 42% of HD patients experienced moderate to extreme pruritus.6 Several smaller studies found that significant itch affects 15%-49% of patients with chronic renal failure and 50%-90% of the dialysis population.7 Most of these studies showed ESRDassociated itch being independent of gender, age, ethnicity and types of dialysis. The prevalence of chronic kidney disease has increased in the last decades and is predicted to continue to rise worldwide,8 suggesting that chronic itch associated with ESRD will remain as a major health problem in this population.Pruritus is common in chronic cholestatic liver disease. It is more ...