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When A Patient Presents With Erythematous Scaling Plaques On The Dorsal Foot

Taking a closer look at the new onset of guttate erythematous plaques in a patient with diabetes, rheumatoid arthritis and a complex surgical history, this author discusses key clinical signs and possible etiologies.

A 62-year-old male with a history of type 2 diabetes mellitus and rheumatoid arthritis presented to the clinic for a follow-up visit on his foot surgery three months earlier. He had a revision of a first MPJ fusion and hammertoe corrections of all the lesser digits. However, the patient related an additional concern of “spots” on his foot that had never been there before. He admitted to having a history of psoriasis but noted that it mainly been isolated to his elbows and knees. Those particular symptoms had not been present in some time and the patient noted he was no longer on medication for psoriasis due to a different recent surgical procedure.

On physical exam, the patient had guttate erythematous plaques with overlying scale in a few areas on the foot. He had no other lesions elsewhere on the body. The lesions were not bothersome. The patient’s concern stemmed from having diabetes and knowing the potentially serious implications of skin changes. The clinical exam suggested this was a psoriatic eruption, specifically palmoplantar psoriasis, due to the patient being off his regular psoriasis medications. We reassured the patient of this and once he resumed his psoriasis medications, the eruption cleared. 

What The Podiatrist Should Know About Palmoplantar Psoriasis 

Psoriasis is a common chronic inflammatory skin disease that has a variety of clinical manifestations and comorbidities. The most common form involves well-demarcated erythematous plaques with overlying scale that presents on the scalp, gluteal cleft and extensor surfaces of the knees and elbows. Forty percent of these patients will have associated palmoplantar psoriasis, which has a reported prevalence ranging from 2.8 to 40.9 percent amongst psoriasis patients.1,2 

Patients with palmoplantar psoriasis will still have erythematous plaques on the feet but they can also develop fissures within the plaques, causing significant pain and disability. One may explain this by the Koebner phenomenon as the feet are certainly a site of constant trauma with ambulation.3 

Concomitant psoriasis of the nails is also common. This consists of such symptoms as pitting, leukonychia, lunula red spots, nail crumbling, “oil drop sign” (tan-brown color of new motor oil), onycholysis, subungual hyperkeratosis, splinter hemorrhages, and nail plate thickening.  

The etiology of psoriasis is unknown as of yet although there are multiple predisposing factors. For example, 40 percent of patients have a positive family history of psoriasis and multiple genes are linked with the disease.3 Other associations include smoking and alcohol usage, obesity, diabetes, inflammatory bowel disease, malignancy, certain medications (such as lithium and Plaquenil (hydroxychloroquine)) and infections. 

Whatever the cause, stimulation of epidermal proliferation results in an increased number of cells, especially those going through DNA synthesis. There is also a shorter cell turnover cycle of 36 hours in comparison with 311 hours in normal skin.3 Histopathology will show uniform epidermal hyperplasia, parakeratosis, neutrophils and possible microabscesses in the strateum corneum, thinning or absence of the granular layer and suprapapillary dermal plate, and tortuous dilated dermal papillary capillaries.3 The diagnosis is mainly clinical although biopsy can certainly help. However, there are no specific labs or genetic tests. 

The most common treatment method is via topical steroids that are reportedly more effective under occlusion.4 When the disease fails to respond or develops into psoriatic arthritis, the use of various other topicals such as retinoids, ultraviolet (UV) therapy and vitamin D analogs may progress into systemic therapies such as cyclosporine, methotrexate and biologics such as Enbrel (etanercept) and Humira (adalimumab).5 Intramuscular steroid injections are another acute therapy option but frequently result in rebound flares.6 Indeed, even with all these treatment methods, psoriasis can prove to be a difficult pathology to control. 

Dr. Vella completed a fellowship in podiatric dermatology and is in private practice in Sun City, Ariz.

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By Joseph Vella, DPM
References
  1. Timotijevic ZS, Trajkovic G, Jankovic J, et al. How frequently does palmoplantar psoriasis affect the palms and/or soles? A systematic review and meta-analysis. Postepy Dermatol Alergol. 2019;36(5):595-603. 
  2. Kumar B, Saraswat A, Kaur I. Palmoplantar lesions in psoriasis: a study of 3065 patients. Acta Derm Venereol. 2002;82(3):192-195. 
  3. Feldman SR. Psoriasis: epidemiology, clinical manifestations and diagnosis. UpToDate.com. Available at: https://www.uptodate.com/contents/psoriasis-epidemiology-clinical-manifestations-and-diagnosis . Updated December 30, 2019. Accessed March 23, 2020.
  4. Obeid G, Do G, Kirby L, Hughes C, Sbidian E, LeCleach L. Interventions for chronic palmoplantar pustulosis. Cochrane Database Syst Rev. 2020;1(1):CD011628. //Is this correct as slight difference in authors?//
  5. Sevrain M, Richard MA, Barnetche T, et al. Treatment for palmoplantar pustular psoriasis: a systematic literature review, evidence-based recommendations and expert opinion. J Eur Acad Dermatol Venereol. 2014; 28 Suppl 5:13-16.
  6. Vlahovic TC, Schleicher SM. Skin Disease of the Lower Extremities: A Photographic Guide. Malvern, Pa., HMP Communications, 2012. 
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