Tuesday, December 25, 2012

Psoriasis vs. PRP: Your Thoughts

Presented by Dr. Henry Foong, Ipoh, Malaysia
Abstract: A 65 year old man presented with a history of erythroderma for 3 weeks.

History: A 65 year old man presented with pruritic scaly erythematous patches on the chest about 3 weeks ago.  Then he noticed the rashes spreading to the abdomen and back.  Now it has spread to the face and both upper and lower extremities. He had no fever or other constituional symptoms.  He denied taking any previous medication or health supplements.There was no past history of psoriasis or eczema.

Examination showed extensive multiple scaly erythematous patches on the abdominal wall, entire back and thighs.  His scalp was scaly too.  Over the lower back and abdominal wall, the erythema was confluent and generalised with multiple erythematous patches with islands of white in between. The lesions has an irregular margin. There is no follicular hyperkeratosis.  The nails were normal. Both palms and soles appeared normal and not hyperkeratotic.


The epithelium shows parakeratosis. The squamous epithelium does not show spongiosis or basal layer degeneration. The upper dermis shows mild perivascular and interstitial infiltrates of lymphocytes and eosinophils. The deep dermis is normal. Features do not suggest psoriasis. 


Features are compatible with pityriasis rubra pilaris without follicular involvement.

Diagnosis: Erythroderma - Extensive psoriasis vs pityriasis rubra pilaris
Reason for posting: This is an interesting diagnostic problem as whether erythroderma is due to PRP or psoriasis.  Though there are features of psoriasiform changes over the extremioties and lower back, the presence of "islands of white" within patches of erythema is suggestive of PRP. As our experience with generalised PRP is limited, it is difficult to make a definitve diagnosis.  A biopsy was done to help to make a more definitive diagnosis.  In terms of treatment, however, oral retinoids such as acitretin would be useful in both conditions.


  1. Great case! Looks more c/w PRP, but has CTCL been considered? Is there access to immunohistochemistry or clonality studies? Either way, isotretinoin or MTX could be used to treat all potential causes--not sure how effective acitretin would be in this case.

  2. Agree differential would start with PRP with psoriasis and CTCL as distant 2nd and 3rd choices. I've had only fair results recently with acitretin, better with MTX, and twice recently had short term success with etanercept. No really great treatment for PRP right now. Do readers feel isotretinoin is better than acitretin?
    Steve Stone

  3. Thank you for your comments and suggestions. They were very helpful. I agree that PRP is the more likely diagnosis after review of the histopath examination. We can perform immunohistochemistry but not clonality studies unless we send the specimen to KL or Singapore for further examination. I am not sure whether to proceed with IHC studies as the history is rather short - it's only 3 weeks duration and the patient has improved with oral acetretin 20mg bd and lots of moisturizers with ung emulsificant and topical betamethasone dipropionate ointment 1:4 str.
    Will certainly do IHC studies if the patient do not respond well to retinoids.
    He was initially treated with oral methotrexate 12.5 mg on the first week but response was very minimal - perhaps too low a dose. He was subsequently changed to oral acitretin 20mg bd which then showed moderate improvement. We did not use any systemic corticosteroids to control the disease.

    I have not treated any PRP with oral isotretinoin before but a review of the literature with pubmed showed there are reports of PRP successfully treated with oral isotretinoin. One such report is by Sehgal et al. Efficacy of isotretion in PRP - Unapproved use. Int J Dermatol. 2006;10;1238-40. The authors described 6 patients successfully treated with oral isotretinoin. There were also other reports of PRP treated with NB-UVB light therapy.


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