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Prurigo nodularis
Evidence Levels: A Double-blind study B Clinical trial ≥ 20 subjects C Clinical trial < 20 subjects D Series ≥ 5 subjects E Anecdotal case reports
Nodular prurigo (NP; also known as prurigo nodularis [ of Hyde] ) is a chronic condition characterized by the presence of highly pruritic, hyperkeratotic papules or nodules, ranging from a few to hundreds in numbers. Accompanying features include severe excoriation, crusting, lichenification, and the presence of postinflammatory hyperpigmentation or hypopigmentation. Lesions are often distributed symmetrically over extensor surfaces of the limbs; the sacral area, abdomen; the face, palms, and genitalia may be affected.
NP may arise at any age but more commonly develops in middle age with a slight female preponderance. It is often regarded as a secondary reaction to chronic pruritus and scratching rather than as a primary cutaneous disease. In over 80% of patients, an underlying cause can be found. This is most commonly atopy, which is present in just under 50% of cases. Cutaneous disorders associated with the development of NP include atopic eczema, venous eczema, allergic contact eczema, dermatitis herpetiformis, Grover disease, lichen planus, and cutaneous lymphoma.
Metabolic diseases have been identified in up to 40% of cases. Diabetes mellitus, thyroid diseases, food (sorbitol, lactose, and fructose) intolerance and malabsorption, iron deficiency, and renal and hepatic failure have all been described. Infections with Helicobacter pylori , hepatitis C and human immunodeficiency virus (HIV), underlying malignancies, and neurologic causes such as neuropathy and chronic pain syndrome have also been reported. Concomitant psychosocial disorders can be found; anxiety and depression may be primary associations or secondary to the chronic pruritus of NP.
Management Strategy
Management should be holistic and directed toward treating the symptoms of pruritus and identifying and correcting any underlying cause. A thorough medical history and physical examination, in combination with relevant investigations, are needed to determine any driver(s) of the itching, whether cutaneous, systemic, or psychological.
General measures such as clipping the fingernails and recommending the use of gloves and mittens can help reduce excoriation. Patients should be encouraged to apply emollients regularly, as xerosis can worsen pruritus. Preparations containing menthol , camphor , or phenol can be useful.
Oral antihistamines are effective for symptom control, and the use of sedating antihistamines such as promethazine 25–75 mg may be helpful at night. Potent topical or intralesional corticosteroid injections (triamcinolone acetonide 40 mg/mL injected in amounts of 0.1 mL/nodule and repeated every 6 weeks) can be used to treat individual lesions. Topical calcineurin inhibitors or topical vitamin D3 analogs may be used as adjuncts or substitutes for topical corticosteroids to ameliorate the risk of skin atrophy associated with prolonged use of the latter. The use of occlusive bandaging or dressings such as hydrocolloid pads, preferably in combination with a topical medication, can interrupt the itch–scratch cycle and facilitate the healing of lesions.
Other oral antipruritic agents include pregabalin 25 mg or gabapentin 300 mg three times a day, or tricyclic antidepressants , such as amitriptyline started at a low dose of 10–25 mg at night. Naltrexone , an opioid receptor antagonist, has been reported to have a potent antipruritic effect in patients with NP. These agents may be more useful for cases with underlying neurologic or psychological causes.
In cases with more widespread involvement, phototherapy with narrowband ultraviolet B (UVB), broadband UVB, psoralens and ultraviolet A (PUVA), or long-wavelength ultraviolet A (UVA1) may be helpful. In severe cases that have failed to respond to topical treatment or phototherapy, systemic immunosuppressive agents such as ciclosporin, azathioprine, and methotrexate can be considered. These may be particularly effective for NP associated with atopic eczema. Thalidomide, due to its side effect profile, should be reserved for patients with debilitating disease in whom all other conventional treatment options have failed.
Recent studies have identified novel therapeutic agents that may effectively treat NP but are still under investigation. These include interleukin (IL)-4 receptor-α inhibitor (dupilumab) , opioid receptor antagonist (nalbuphine ), the neurokinin 1 receptor (NK1r) antagonist (serlopitant), and the anti-IL-31 receptor A agent nemolizumab.
In cases of NP with an identifiable underlying cause, treatment should be directed toward correcting this; for example, prescribing iron supplements in iron-deficiency anemia.
Specific Investigations
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Diagnostic and treatment algorithm for chronic nodular prurigo
Ständer HF, Elmariah S, Zeidler C, et al. J Am Acad Dermatol 2020; 82: 460–8.
A review of the diagnostic assessment, workup, and treatment algorithm for patients with chronic NP.
Evaluation of the antipruritic effects of topical pimecrolimus in nonatopic prurigo nodularis: results of a randomized, hydrocortisone-controlled, doubled-blind phase II trial
Siepmann D, Lotts T, Blome C, et al. Dermatology 2013; 227: 353–60.
The antipruritic effects of 1% hydrocortisone and 1% pimecrolimus creams are compared in this within-participant, right–left, controlled trial involving 30 patients. A significant reduction in pruritus intensity was achieved on both pimecrolimus- and hydrocortisone-treated sites. No therapeutic difference between pimecrolimus and hydrocortisone was found. Dermatology Life Quality Index scores among subjects improved significantly after treatment.
This is one of very few comparative trials of topical therapies for NP. Although this study looked at the relative efficacy of hydrocortisone, other studies had employed the use of at least potent-strength topical corticosteroids. The highly pruritic nature of NP is such that the use of potent or superpotent topical corticosteroids is often necessary and should be used as first-line treatment.
Treatment of pruritic diseases with topical calcineurin inhibitors
Ständer S, Schurmeyer-Horst F, Luger TA, et al. Ther Clin Risk Manag 2006; 2: 213–8.
Eleven patients were treated with twice-daily application of topical pimecrolimus or tacrolimus. Five patients achieved 70% or greater reduction of itch with healing or major improvement of lesions.
Topical calcineurin inhibitors are known to have antipruritic and immunosuppressive effects in atopic eczema and, as demonstrated in this study, in non-atopic NP. They represent an effective and non-atrophogenic alternative to topical steroids and may potentially be a safer option for long-term use.
An occlusive dressing containing betamethasone valerate 0.1% for the treatment of prurigo nodularis
Saraceno R, Chiricozzi A, Nistico SP, et al. J Dermatolog Treat 2010; 21: 363–6.
A bilateral-paired comparison study involving 12 patients comparing 0.1% betamethasone valerate tape against a moisturizing itch-relief cream containing feverfew. Occlusion enhanced the efficacy of treatment, preventing scratching, and the side treated with betamethasone valproate 0.1% tape demonstrated a higher clinical response.
Use of occlusive membrane in prurigo nodularis
Meyers LN. Int J Dermatol 1989; 28: 275–6.
Four patients with NP responded to weekly application of an occlusive hydrocolloid pad, which also served as a negative reinforcer of scratching.
The use of adhesive occlusive pads, dressings, or bandaging can serve as a deterrent to repetitive scratching of the skin that perpetuates the disease and can disrupt the itch–scratch cycle.
Double-blind, right/left comparison of calcipotriol ointment and betamethasone ointment in the treatment of prurigo nodularis
Wong SS, Goh CL. Arch Dermatol 2000; 136: 807–8.
A randomized, double-blind, right/left comparative study evaluating the efficacy of calcipotriol ointment vs. 0.1% betamethasone valerate ointment in 30 patients. Calcipotriol was found to be more effective than betamethasone valerate after 8 weeks of treatment, with a greater reduction in number and size of nodules from baseline.
Topical vitamin D3 (tacalcitol) for steroid-resistant prurigo
Katayama I, Miyazaki Y, Nishioka K. Br J Dermatol 1996; 135: 237–40.
Nine of 11 patients treated with twice-daily application of topical tacalcitol showed a significant clinical response within 4 weeks.
Phototherapy in nodular prurigo
Divekar PM, Palmer RA, Keefe M. Clin Exp Dermatol 2003; 28: 99–100.
The responses of 14 patients treated with a total of 19 courses of phototherapy (8 courses of broadband UVB, 4 courses of bath PUVA, and 7 courses of oral PUVA) are reported. Partial resolution was achieved in 68% of treatment courses. Complete resolution occurred in three patients, but two relapsed within 1 year.
Narrow-band ultraviolet B phototherapy in patients with recalcitrant nodular prurigo
Tamagawa-Mineoka R, Katoh N, Ueda E, et al. J Dermatol 2007; 34: 691–5.
Ten patients with recalcitrant NP received once-weekly narrowband UVB therapy. Complete or marked clearance was achieved in all patients after a mean cumulative dose of 23.88 J/cm 2 over a mean of 24 sessions. At 1-year follow-up, only one patient had relapsed.
Phototherapy of generalized prurigo nodularis
Bruni E, Caccialanza M, Piccinno R. Clin Exp Dermatol 2010; 35: 549–50.
Nineteen patients with generalized NP who had failed a range of previous therapies, including topical corticosteroids, coal tar, oral antihistamines, and ciclosporin, were treated with phototherapy mainly in the UVA range with a spike at 390 nm. A median number of 23 sessions, with a mean total dose of 6.07 J/cm 2 , was required. Out of 15 patients who improved with treatment, two patients achieved complete remission, and eight patients achieved marked improvement.
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