DIAGNOSIS AND TREATMENT OF LOCALIZED NEUROPATHIC PAIN SECONDARY TO KERATOACANTHOMA CENTRIFUGUM MARGINATUM
Background: We report a case of pain secondary to keratoacanthoma centrifugum marginatum (KCM) ,who was diagnosed with screening tool for the diagnosis of neuropathic pain.
Case report: 54 year old male with a history of type 2 diabetes mellitus, with pain secondary to KCM. He was treated with 5-fluorouracil topical and acitretin, intralesional methotrexate, topical imiquimod 5%, retinoids, radiotherapy and curettage. The patient did not receive analgesic treatment. Pain intensity by visual analog scale (VAS) was 7,accompanied by electric discharge in the back and first finger of right hand  in relation to the cures, and paresthesias in this area. On examination, showed a wound of 20x20 cm, with areas of scarring; allodynia and hyperalgesia in the back of the hand and first finger of his right hand. For diagnosis, screening tool was used. He was treated with lidocaine patch 5% ,and tramadol 50mg one hour before to cures. The patient showed an improvement of sensory symptoms and pain (VAS 3).
Discussion: KCM is a rare variant of keratoacanthoma .It is characterized by a progressive peripheral expansion and central healing leaving atrophic scar. To date, only 40 cases have been reported worldwide1. In our case, the patient had a localized neuropathic pain, that was easy to detect using a new tool for detection of neuropatic pain and the subtype, localized neuropathic pain ,the screening tool. It is accurate and easy to use. It consists of four questions, in addition to the information regarding each of these issues, and a detailed algorithm. A spanish version and a version in english, are available today in the form of a wallet card2. 
References:
1. Yang Y, Xu Y, Wang L, et al. Two cases of giant keratoacanthoma centrifugum marginatum accompanied by α-human papillomavirus infection. Int J Dermatol. 2015 Aug;54(8):951-4.
2. Mick G, Baron R,Correa G, et al.Is an easy and reliable diagnosis of localized neuropathic pain (LNP) possible in general  practice? Development of ascreening tool .Abstract 3145; XXI WCN2013; Sept 2013.
Learning points:The literature has  forgotten  the painful symptoms of KCM, that , as in the case presented, can be very disabling for the patient. The use of the screening tool allowed us a quick, easy and effective diagnosis. Treatment guidelines for neuropathic pain consider the presence of localized pain in the choice of first-line treatment, recommending the lidocaine patch 5%.

Diagnosis and treatment of localized neuropathic pain secondary to keratoacanthoma centrifugum marginatum