Bilaterally symmetrical SKINTED: A rare entity

A 50-year-old female presented with gradual onset, itchy red coloured lesions over both knees for 3–4 months. The patient underwent bilateral total knee replacement surgery 6 months back and developed itching and red lesions 4–6 weeks after the procedure. Initially, lesions appeared over the right knee and later involved the contralateral knee in another 1–2 weeks. On examination, bilaterally symmetrical erythematous plaques with fine scaling were noted over the anterior and inferolateral aspects of the knee, with sparing of the medial aspect [Figure 1]. The lesions resolved after treatment with topical emollients, topical corticosteroids and oral antihistamines for 2 months. Based on the above findings, a diagnosis of Surgery of the Knee, injury to the Infrapatellar branch of the saphenous Nerve, Traumatic Eczematous Dermatitis (SKINTED) was made.

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Figure 1:

Bilaterally symmetrical eczematous eruption over the front and inferolateral aspect of the knee with sparing of the medial aspect.

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The anterior and inferolateral aspect of the knee is supplied by a pure sensory nerve, i.e., the infrapatellar branch of the saphenous nerve. It has a subcutaneous course, which makes it susceptible to injury, especially during midline incision as in total knee replacement surgery. Transection of this nerve results in paresthesia and anesthesia of variable severity and uncommonly, produces pruritic eczematous dermatitis specifically localized to the front and inferolateral aspect of the knee. This dermatitis has been designated as autonomic denervation dermatitis, neuropathy dermatitis, or post-traumatic eczema. Recently, an acronym Surgery of the Knee, injury to the Infrapatellar branch of the saphenous Nerve, Traumatic Eczematous Dermatitis (SKINTED), is a site-specific dermatitis, i.e., SKINTED has been suggested for this dermatitis occurring specifically over the anterior and inferolateral aspect of the knee after total knee replacement surgery. The specific localization to aforementioned sites with sparing the medial aspect of the knee, helps in differentiating it from other eczematous dermatitis over a similar site.^[1]

An important differential diagnosis of SKINTED is metal hypersensitivity dermatitis, which is a rare complication of total knee arthroplasty and is seen with cobalt–chromium metal implants. Metal hypersensitivity dermatitis generally presents with painful and persistent synovitis, synovial effusion, and even implant failure. The cutaneous manifestations are less frequent and appear 2 months–2 years after the procedure as an eczematous dermatitis on either side of the surgical scar. The cutaneous involvement may be generalized with involvement up to the neck, gluteal area, and extremities. The pruritus and recurrences are more than those of SKINTED, and there is no associated hypoesthesia. There is an associated history of metal allergy in the patient and/or the family.^[2,3] Allergic contact dermatitis to iodine or dressing can also occur; however, it presents early within 5–14 days of exposure to the incriminated agent as erythematous papules or vesicles localized to the area of application.^[4,5]