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Pruritus (itch) is the unpleasant sensation of the skin that results in a desire to scratch. It is a major symptom of many cutaneous and systemic diseases. Pruritus can range from mild to severe, and may be intermittent or chronic (lasting longer than 6 weeks). Pruritus can have a significant impact on health-related quality of life (HRQOL), and has been associated with depression, decreased sleep quality, and global distress.1 The authors of a recent case-control study of patients with chronic pruritus observed that the impact of chronic pruritus on HRQOL may be similar to that of chronic pain.2 Pruritus has multiple etiologies in patients with and without underlying skin disease. The International Forum for the Study of Itch published a clinical classification of pruritus3 in which they proposed 6 categories for pruritus based on the underlying origin:

  1. Dermatological: Pruritus associated with diseases of the skin, including diseases that feature prominent pruritus such as atopic dermatitis, allergic contact dermatitis, xerotic dermatitis, lichen simplex chronicus, lichen planus, scabies, and urticaria. These diseases typically have characteristic skin findings.

  2. Systemic: Pruritus associated with diseases in organs other than the skin, such as the liver, kidneys, hematopoietic system, etc.

  3. Neurological: Pruritus associated with diseases or disorders of the central or peripheral nervous system.

  4. Psychogenic/psychosomatic: Pruritus associated with psychiatric disorders.

  5. Mixed: Pruritus from combinations of categories 1 to 4.

  6. Other: Pruritus of undetermined origin.

Typically, the pruritus in categories 2 to 6 is associated with no primary skin lesions. However, secondary lesions from scratching or rubbing, such as excoriations (Figure 26-1), prurigo nodularis (Figure 26-2), or lichenification can be seen. It is important to determine the etiology of chronic pruritus, because it can be an early symptom of the diseases in categories 2 to 4. Table 26-1 contains information about selected diseases that are associated with chronic pruritus.

Figure 26-1.

Excoriations in a patient with no underlying skin disease. Excoriations with postinflammatory hyperpigmentation on back.

Table 26-1.Differential diagnosis of pruritus in patients with no underlying skin disease.

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