Pruritis with Rash

Pruritus, or itching, is the most common dermatologic complaint. When pruritus occurs with cutaneous findings, the clinician must carefully analyze the dermatologic findings to identify the underlying cause. Severe pruritus may lead to lifestyle disturbances by causing anxiety, depression, and loss of sleep. Pruritus without a rash should result in a search for systemic causes, such as liver disease.

Differential Diagnosis

• Infectious causes
  –Fungal infections: Dermatophyte infections (tinea), candidiasis (beefy red color with satellite papules), seborrheic dermatitis (from Pityrosporum, common in hair-bearing areas, with scale)
  –Bacterial infections: Erythrasma (from Corynebacterium), frequently in axilla
  –Viral infections: Chicken pox (Varicella)
  –Insect vectors: Scabies, pediculosis or lice (also present on spouse and other family members), flea bites (typically on legs), mosquito bites (central punctum)
  –Mixed infections: Intertrigo (present at skin folds or area of friction)
• Noninfectious causes
  –Contact dermatitis (e.g. rhus dermatitis): May be revealed in contact history, linear vesicular lesions with sharp margins
  –Atopic dermatitis: Erythematous rash in flexural areas, patient with seasonal allergies and/or asthma
  –Eczematous dermatitis: Stasis dermatitis (hyperpigmented legs of patients with vascular disease), lichen simplex chronicus (anxious patient who chronically scratches), dyshidrotic eczema (on hands and feet with scaling, erythema, and minute vesicles and painful fissures), nummular eczema (round scaly lesions on dry skin, common in the winter)
  –Pityriasis rosea: Mostly on trunk in “Christmas tree” pattern, begins as single, larger “herald” patch
  –Lichen planus: Koebner reaction (lesions occur with trauma, such as linear lesions from scratching), purple, polygonal, pruritic papules
  –Psoriasis: Koebner reaction, pink, silvery scaling plaques, extensor surfaces, nail pits
• Less common etiologies (“zebras”) include mycoses fungoides (referred to as Sézary syndrome if erythroderma, lymphadenopathy, and atypical circulating white blood cells are present), dermatitis herpetiformis, miliaria (heat rash)

Workup and Diagnosis

• History and physical examination
  –Past medical and family history (e.g., asthma, psoriasis) and exposure history (e.g., poison ivy, oak, or sumac) are important, including whether the lesions are occurring for the first time or are recurrent
  –Perform a total body skin exam to evaluate distribution of rash; evaluate especially for rashes on the extensor or flexor surfaces of skin folds, and interdigital spaces
  –Note the morphology of the lesion (e.g., macule, papule, pustule, plaque, crust, vesicle, bulla, wheal)
  –Note the configuration of the lesion [e.g., linear (Koebner reaction or contact), grouped, annular, geographic]
• Scrape lesions and perform KOH test if fungal infection is suspected (hyphae visible in dermatophyte infections, and pseudohyphae visible in Candida infections)
• Wood's lamp test: Erythrasma turns coral red
• Scrape possible burrow site to identify a mite in scabies
• Patch testing may be done if allergic contact dermatitis is suspected
• Punch biopsy may be done to establish a histologic diagnosis (e.g., mycosis fungoides)
• Anti-gliadin antibodies and/or anti-endomysial antibodies may be found in the serum of patients with dermatitis herpetiformis
• Consider referral to a dermatologist if diagnosis remains unclear

Treatment

• Symptomatic treatment is often sufficient
  –Take cool or lukewarm rather than hot baths and showers; wash with a mild soap and apply soap only to malodorous areas
  –Apply an emollient immediately after bathing; emollients with menthol provide a cooling sensation; emollients with phenol or camphor provide an anesthetic effect
  –Oral antihistamines such as hydroxyzine or diphenhydramine may be used but are sedating
  –Nonsedating antihistamines are not effective in reducing pruritus
• Fungal infections: Topical or oral antifungal agent
• Scabies: Permethrin cream or Lindane_^R lotion
• Contact dermatitis: Remove offending agent
• Eczematous dermatitis, lichen planus: Topical steroids
• Psoriasis: Steroids, tars, retinoids, UVB light, immune modulator drugs

Book Source Details

• Book Title: In a Page: Signs and Symptoms
• Author(s): Scott Kahan, Ellen G. Smith
• Year of Publication: 2004
• Copyright Details: In a Page: Signs and Symptoms, Copyright © 2004 Lippincott Williams & Wilkins.

Other Book Chapters Related to Rash

Read excerpts from these other book chapters related to Rash:

Copyright Details: In a Page: Signs and Symptoms, Copyright © 2008 Williams & Wilkins.

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• Back to symptom: Rash: Introduction (review 1085 causes)
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More About This Book: Title: In a Page: Signs and Symptoms Authors: Scott Kahan, Ellen G. Smith Publisher: Lippincott Williams & Wilkins Copyright: 2004 ISBN: 1-4051-0368-X