Saturday, January 01, 2011
Prurigo nodularis is a morphologic lesion that
is a consequence of severe and repeated scratching of one area. In
most patients it is secondary to an underlying pruritic condition
such as photosensitive dermatitis, renal failure, or neuropathic
pruritus due to nerve impingement (brachioradial pruritus). Rarely,
bullous pemphigoid may present as prurigo nodularis (pemphigoid
nodularis). In some persons, no underlying condition is found.
Prurigo nodularis is often very difficult to manage.
Prescribe high-potency to superpotent
topical steroids to be applied 2-4 times daily with or without
If there are only a few lesions,
intralesional triamcinolone acetonide 5-10 mg/cc to the mid-dermis
of the lesion is often of great benefit.
Hydroxyzine or diphenhydramine 25-75 mg
before bed and as tolerated 3 times daily.
During the initial visit, an assessment of
the patient's mental status is essential. Depression may be
present, either as a cofactor in causing the condition, or as a
consequence of the chronic, intractable itching.
As a part of the initial evaluation, the
cause of the itching should be determined. Dermatitic and
neuropathic causes of itching should be sought with appropriate
evaluations: skin biopsy; laboratory testing for renal, liver, and
endocrine function and anemia; and neurological evaluation for
neuropathic pruritus. In some patients, no cause will be
If the lesions are localized to one area,
lidocaine impregnated patches 5% may be very effective.
If occlusion with superpotent steroids
and/or intralesional therapy fails, consider covering the affected
extremities with an occlusive dressing (eg, an Unna boot), changing
it weekly every week for 2-4 weeks. If the patient does not remove
the dressing or manipulate the lesions beneath it, lesions usually
will improve, and after 2-3 weeks the itching will begin to subside
in a subset of patients.
If standard antihistamines are of no
benefit, antianxiety agents (e.g., alprazolam) or tricyclics (e.g.,
doxepin) may help. Mirtazapine 25-75 mg nightly may also be an
Thalidomide is dramatically beneficial,
especially in patients in whom no underlying cause is identified.
Since patients are at high risk for the development of neuropathy,
begin thalidomide at 50 mg every other day, and increase to 50 mg
daily after 6-8 weeks if there has been no response. Most patients
respond to doses of 100 mg per day or less. While doses up to 400
mg per day can be used, these high doses dramatically increase the
risk of side effects.
Isotretinoin and acitretin in standard acne
or psoriasis doses, respectively, may be used as adjunctive
treatment in patients with prurigo nodularis.
Polymorphous light eruption, especially in
Native Americans, may appear identical to prurigo nodularis on the
extensor surfaces of the upper extremities. Hypertrophic lichen
planus, lichen amyloidosis, and discoid lupus erythematosus also
may be clinically similar.
Lesions similar to prurigo nodularis can
occur in occasional patients with bullous pemphigoid.
Thalidomide is a potent teratogen. It should
only be used in otherwise unmanageable patients, by those skilled
in its use, and never in women of child-bearing potential.
Thalidomide is associated with the
development of sensory neuropathy in up to 45% of patients with
prurigo nodularis. The daily dose should be kept at the minimum
required. If the maintenance dose is more than 50 mg per day,
regular neurological evaluations should be undertaken.
Thalidomide is associated with venous
thrombosis and stroke when used in doses above 100 mg per day.
Anticoagulation should be considered in these patients.