PRURITUS
PRURITUS: Excerpt from Differential Diagnosis in Primary Care
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.
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 lymphoma 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 pruritus.
Any vaginal discharge may cause pruritus vulvae. Thus, Trichomonas and Candida organisms 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
-
CBC (leukemia, polycythemia)
-
Chemistry panel (liver disease, uremia)
-
Thyroid profile (hyperthyroidism)
-
Glucose tolerance test (diabetes mellitus)
-
Protein electrophoresis (lymphoma, myeloma)
-
CT scan of abdomen (malignancy)
-
Skin biopsy
-
Dermatology consult
Pictures
Book Source Details
- Book Title: Differential Diagnosis in Primary Care
- Author(s): R. Douglas Collins MD, FACP
- Year of Publication: 2007
- Copyright Details: Differential Diagnosis in Primary Care, Copyright © 2007 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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