PRURIGO NODULARIS

Prurigo nodularis (PN) is a nodular form of lichen simplex chronicus. Both adult men and women are affected. The patient complains of intense itching and/or the inability not to scratch. It is very common for the patient to say, "My skin does not heal". The truth is that their skin would heal normally if they stopped scratching.

• It is not unreasonable to screen for chronic kidney disease, diabetes and liver disease as these are common comorbidities.
  
• Associations include African-American race, chronic kidney disease, hepatitis C, chronic obstructive pulmonary disease, congestive heart failure, depression and atopic dermatitis.
  
• About half of patients have atopic dermatitis.
  
• Sleeplessness is common.
• In Europe they call it chronic prurigo and have various subtypes including ulcerative prurigo, prurigo nodularis etc. In the US, we just call it PN, even if there aren't discrete nodules.

The patient develops hyperkeratotic, lichenified papules and nodules at sites of repeated scratching. The extensor surfaces of the extremities are typically affected. Excoriations and erosions are common. Secondary bacterial infection may occur. One key diagnostic feature is that the skin changes do not occur on the areas where the patient cannot scratch, e.g. the middle of the back--the butterfly effect.

Patients complain of itch, but also quite common are burning, pain and a stinging sensation.

Differential Diagnosis

Rarely some cases of bullous pemphigoid (pemphigoid nodularis) are similar, so one can do DIF (which should be negative in PN).

Workup

Usual--CBC, LFT, creatinine, thyroid, HbA1c As Indicated--HIV, hepatitis, skin biopsy/DIF, Imaging (e.g CXR), spep, IgE, TB testing.

RegionalDerm

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