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Difficulty differentiating palmar psoriasis from eczema: Can dermatopathologists lend a Hand?

DII small banner By Warren R. Heymann, MD
July 2, 2017

palmar psoriasis
Clinical manifestations of palmar skin lesions. A, Palmar psoriasis appeared as scattered hyperkeratotic scaly round patches over the entire palm. B, Hand eczema appeared as scaly patches on the palm and phalanges. C, Hyperkeratotic hand dermatitis appeared as sharply demarcated areas of thick scaling and painful fissures on the proximal and middle of the palm.
Credit: JAAD

I have had the privilege of learning from a master clinician, Ed Bondi, at Penn since I was a dermatopathology fellow. Ed is a brilliant dermatologist who “inherited” Walter Shelley’s practice right out of his residency. Can you imagine that? One of Ed’s teachings is to be careful diagnosing chronic hand (or foot) eczema, as it may really be psoriasis. Certainly, it is easier if the patient has psoriatic plaques elsewhere or characteristic nail changes. Without those features, it may be a real challenge. Some may consider the point moot — does it really matter if you’re going to treat with similar therapies? (Although treatments may be similar, a correct diagnosis is always preferable, especially in this era of biologics — would dupilumab be an appropriate choice for psoriasis?)

After ruling out infectious etiologies such as tinea magnum (by KOH or culture) or allergic contact dermatitis (by patch testing), how do you secure the right diagnosis? Clinical-pathologic correlation should confirm infrequently encountered disorders such as cutaneous T-cell lymphoma (notably Woringer-Kolopp disease) (1), Basex syndrome (2), syphilis (3), or necrolytic acral erythema (4). Assuming no zebras are identified, does a routine skin biopsy help differentiate psoriasis from chronic hand eczema?
Park et al retrospectively analyzed the histology of hematoxylin-eosin-stained sections obtained from 96 patients diagnosed with palmar psoriasis (PP), hand eczema (HE), or hyperkeratotic hand dermatitis (HHD). Patients were divided into 4 subgroups: PP (n = 16, group A), HE without atopic or nummular dermatitis (n = 41, group B), HE with atopic or nummular dermatitis (n = 14, group C), and HHD (n = 25, group D). Loss of the granular layer (group A 62.5%, group B 24.4%, group C 0%) was more consistent with a diagnosis of PP (P = .047) than HE (P = .002). Psoriasiform epidermal hyperplasia (group B 36.6%, group C 35.7%, group D 72.0%) favored a diagnosis of HHD (P = .01) over HE (P = .043). The authors concluded that their study demonstrated a significant difference in the thickness of the granular layer between PP and HE, which might be helpful in differentiating between these 2 conditions. There was no difference between PP and HHD. (5)
Can dermoscopy help? Ten patients with biopsy-proven palmar psoriasis and 11 patients with biopsy-proven chronic hand eczema were evaluated by dermoscopy. The authors found that the presence of diffuse white scales was significant in palmar psoriasis whereas the presence of yellowish scales, brownish-orange dots/globules and yellowish-orange crusts was significant in chronic hand eczema. (6) I agree with the conclusions of the authors based on the findings in their paper, however, it is not the patient with “biopsy-proven” disease that concerns me. If there is classical histology for either psoriasis or hand eczema, the dermoscopy will correlate as they describe. I look forward to seeing if it helps in such cases where the histology is equivocal.

Posada et al obtained 77 biopsies – 41 from palms and 35 from soles (in 1 case the origin was not specified); 45 biopsies were hyperkeratotic lesions and 32 were vesiculopustular lesions. The group of patients included 40 men and 37 women aged between 8 and 83 years. All the biopsies were evaluated by the same pathologist. Only 10% of the biopsies and gave definitive diagnoses – 2.6% psoriasis and 5.2% eczema. Most importantly, 68% were inconclusive. The percentage of biopsies that led to a change in initial empirical treatment was low: 1.3%. (7)

Although I will utilize the observation about the diminished granular layer being a reasonable histologic diagnostic clue in differentiating palmar psoriasis from hand eczema, I have to concur with Posada et al:

In conclusion, biopsies from palms or soles with hyperkeratotic or vesiculopustular symptoms have low diagnostic yield. For each change of treatment, 77 biopsies are required and 11 patients suffer discomfort for more than a week. Therefore, we recommend avoidance of this practice and the use of other diagnostic tools, such as direct examination with potassium hydroxide or culture. Once infectious causes are ruled out, empirical treatment is justified and biopsy should only be used where there is consideration of differential diagnoses in which clear histological differentiation can be expected.

I am confident that in the near future, non-invasive techniques (dermoscopy, reflective confocal microscopy, optical coherence tomography, or yet-to-be discovered modalities) will be guiding our therapeutic decisions for those patients that make even the most season clinicians wonder if psoriasis or eczema is the problem.

1. Wang SC, Mistry N. Woringer-Kolopp disease mimicking psoriasis. CMAJ 2015; 187: 1310.
2. Koh WL, et al. Psoriasiform dermatitis in a case of newly diagnosed locally advanced pyriform sinus tumour: Basex syndrome revisited. Singapore Med J 2012; 53: e12-4.
3. Solak B, et al. Palmoplantar syphilis misdiagnosed and treated as palmoplantar psoriasis for 2 years. J Family Med Prim Care 2016; 5: 506.
4. Kapoor R, Johnson RA. Necrolytic acral erythema. N Engl J Med 2011; 364:1479-80.
5. Park JY, et al. The histopathological differentiation between palmar psoriasis and hand eczema: A retrospective review of 96 cases. J Am Acad Dermatol 2017; 77: 130-5.
6. Errichetti E, Stinco G. Dermoscopy in differential diagnosis of palmar psoriasis and chronic hand eczema. J Dermatol 2016; 43: 423-5.
7. Posada C, et al. Value of palmar and plantar biopsies of hyperkeratotic and vesicular pustular lesions: A cross-sectional study. Actas Dermosifiliogr 2010; 101: 103-5.

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