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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?

After obtaining a complete history and physical examination, what clinically oriented classification scheme should be followed?

New diagnostic tools are evolving to better evaluate patients with pruritus. The International Forum for the Study of Itch has published a clinical classification utilizing the physician exam to provide physicians with a framework for improving the care of the pruritic patient.

Patient can be classified as group I, patient with pruritus on diseased inflamed skin; group II, patients with pruritus on normal noninflamed skin; and group III, patients with pruritus on chronic secondary reactive lesions such as scratching/rubbing (Table 67-2).

Diagnostic tests for group I include a skin biopsy and laboratory investigation, such as IgE or indirect immunofluorescence. Diagnostic tests for group II include a laboratory and radiologic investigation based on the patient’s history. Diagnostic tests for group III include a skin biopsy and laboratory and radiologic investigation based on patient’s history.

Initial tests include

Skin biopsy
Complete blood count and differential
Liver function tests, including alkaline phosphatase for obstructive liver disease
Renal function testing, including blood urea nitrogen, creatinine, and urinalysis
Optional tests including thyroid function tests and chest x-ray

Other tests based on patient’s history and preexisitng diseases include a fasting glucose, stool exams for occult blood, Papanicolaou smear, serum iron, serum protein electrophoresis, urine for 5-hydroxyindoleacetic acid (5-HIAA), urine for mast cell metabolites, skin biopsy with direct immunofluorescence (to exclude dermatitis herpetiformis and bullous pemphigoid), and biopsy with special stains (to exclude mastocytosis).

Stander S, Weisshaar E, Mettang T, et al: Clinical classification of itch: a position paper of the International Forum for the Study of Itch, Acta Derm Venereol 87:291–294, 2007.

Table 67-2. Classification of Generalized Pruritus
	CATEGORY	DISEASES
	I. Dermatologic (arising from diseases of the skin)	Xerosis (dry skin), atopic dermatitis, contact dermatitis, urticaria, bullous pemphigoid, dermatitis herpetiformis, lichen planus, mastocytosis, polymorphic eruption of pregnancy, prurigo gestationis, cutaneous T-cell lymphoma, other leukemic infiltrates
	II. Systemic (arising from diseases of organs other than the skin, such as liver, kidney, blood, and drugs)	Uremia, cholestasis, primary biliary cirrhosis, chronic renal failure, HIV infection, dermatophysis, drugs, polycythemia rubra vera, Hodgkin’s lymphoma, iron-deficiency anemia, carcinoid syndrome, druginduced pruritus, solid tumor (such as colon, prostate), perimenopausal pruritus
	III. Neurologic (arising from disease of the central nervous system or peripheral nervous system	Multiple sclerosis, neoplasms, cerebral or spinal infarcts, brachioradial pruritus, notalgia paresthetica, postherpetic neuralgia, vulvodynia
	IV. Psychogenic/psychosomatic (somatoform pruritus)	Depression, anxiety disorders, obsessive-compulsive disorders, schizophrenia
	V. Mixed (overlapping and coexistence of several diseases)
	VI. Other