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Approaching the Pruritic Patient

»	What is the most common symptom of dermatologic disease?
»	What is an “itch”?
»	Is an itch a separate modality of pain or a submodality of pain?
»	What causes an itch?
»	Describe the difference between localized and generalized pruritus.
»	What is the best approach to evaluation of a patient with localized pruritus?
»	What are the common causes of localized pruritus?
»	What is notalgia paresthetica?
»	What is the physician’s best approach when seeing a patient with generalized pruritus?
»	After obtaining a complete history and physical examination, what clinically oriented classification scheme should be followed?
»	What are common causes of generalized pruritus?
»	How prevalent is an underlying systemic disease in a patient who seeks medical attention for pruritus?
»	What is “winter itch”? In which patient population is it common?
»	The patient complains that “wool makes me itch” or “I am allergic to wool.” What disease does this patient probably have?
»	What treatment should the physician consider if a patient presents with pruritus and “hives”?
»	What disease should the physician consider if the patient volunteers that his spouse also suffers from itching?
»	Is pruritus in HIV-infected patients common? What are the common causes of pruritus in these patients?
»	Which psychiatric disorder often presents with intractable pruritus?
»	Which patients with renal failure experience “renal itch”?
»	Which patients with liver disease are most likely to experience pruritus? What is the best screening laboratory test?
»	What are the common causes of cholestic pruritus?
»	Which hematologic disorders are known to present with pruritus?
»	Is generalized pruritus a common symptom of endocrine disorders?
»	Can itching cause skin disease?
»	What is the best symptomatic treatment for a patient with pruritus?

Is an itch a separate modality of pain or a submodality of pain?

Cutaneous nerve fibers arranged in an arborizing plexus immediately below the epidermis receive itch impulses. Unmyelinated C fibers conduct itch impulses from the skin to the ipsilateral dorsal root ganglia, ascend in the opposite anterolateral spinothalamic tract (closely associated with pain fibers), continue to the thalamus, and proceed through the internal capsule to the sensory cortex.

Although controversial, the general consensus views an itch as a separate modality of pain. Though distinguishing between the sensations of pain and pruritus is easy, distinguishing between the neurophysiology of pruritus and pain is not. Pruritus and pain share many neurophysiologic features and pathways. The following factors support that pain and itch are separate and distinct sensations: Itch leads to the reflex or urge to scratch; pain leads to withdrawal. Itch occurs only in the skin; pain arises from deeper structures as well. Heat may stop itch; heat usually increases pain. Removal of the epidermis eliminates itch; removal of the epidermis causes pain.