PRURITUS

The differential diagnosis of pruritus is best developed by anatomy. Local conditions such as bites and parasitic infestations (e.g., scabies, hookworms, and schistosomiasis) usually reveal an obvious lesion. Generalized skin conditions such as dermatitis herpetiformis, atopic dermatitis, and exfoliative dermatitis are also more likely to show obvious skin manifestations and severe itching. These conditions are to be distinguished from cutaneous syphilis, where there is no itching at all, and psoriasis and pemphigus, where the itching is minimal. Numerous other skin conditions cause pruritus, but we are more concerned with the systemic causes because they are more difficult to diagnose.

PRURITUS

Jaundice, particularly obstructive jaundice, is associated with marked pruritus. Primary biliary cirrhosis may begin with pruritus without jaundice because the liver must turn more than 30 g of bile salts (the cause of the itching) a day to only 1 g of bilirubin. Thus, although there may be enough function left to turn over the bilirubin, there is not enough to turn over the bile salts.

Diabetes mellitus may cause pruritus, particularly vulvar, where it predisposes to moniliasis. Renal disease may also cause pruritus, presumably because of the retention of toxic waste products. Finally, leukemia and Hodgkin disease are systemic causes of pruritus. Of course, psychoneurosis and malingering must be considered.

In addition to systemic conditions mentioned above, one should search for local conditions in the anus and rectum (pruritus ani), especially hemorrhoids (internal ones may not be obvious), anal fissure, anal abscess or fistula, and anal moniliasis or pinworms. Condyloma acuminatum may contribute to pruritis.

Any vaginal discharge may cause pruritus vulvae. Thus, Trichomonas and Candidaorganisms should be looked for. One should also consider lack of estrogen leading to atrophic vaginitis and dermatitis.

Approach to the Diagnosis

It should be obvious that the clinical approach to pruritus without an obvious dermatologic manifestation is to order appropriate tests. See below to rule out the above systemic disorders.

Other Useful Tests

1. CBC (leukemia, polycythemia)
2. Chemistry panel (liver disease, uremia)
3. Thyroid profile (hyperthyroidism)
4. Glucose tolerance test (diabetes mellitus)
5. Protein electrophoresis (lymphoma, myeloma)
6. CT scan of abdomen (malignancy)
7. Skin biopsy
8. Dermatology consult

Book Source Details

• Book Title: Differential Diagnosis in Primary Care
• Author(s): R. Douglas Collins
• Year of Publication: 2007
• Copyright Details: Differential Diagnosis in Primary Care, Copyright © 2007 Lippincott Williams & Wilkins.

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More About This Book: Title: Differential Diagnosis in Primary Care Authors: R. Douglas Collins Publisher: Lippincott Williams & Wilkins Copyright: 2007 ISBN: 0-7817-6812-8