Systemic methotrexate for prurigo nodularis and keratoacanthomas in actinically damaged skin.

We previously reported a cohort of elderly patients with concurrent development of debilitating prurigo nodularis, extreme and disabling pruritus with or without eczematous dermatitis, and keratoacanthomas in the presence of actinic damage.1 This report is a long-term follow through on patients who were successfully transitioned from cyclosporine, acitretin, and topical 5-fluorouracil to subcutaneously administered methotrexate. We believe that an underlying dysregulation of both inflammatory and cell growth pathways predisposes these individuals to the development of both types of lesions.1 Three of the patients have since been successfully treated with systemic methotrexate and are described below. We stated in our original report that no patients had keratoacanthomas while on cyclosporine and acitretin; however, in reviewing the material for this follow-up report, keratoacanthomas were noted in the patients' files. These lesions were existing lesions that did not clear after the initiation of therapy and were deemed suspicious enough for further evaluation. Herein we describe patients who underwent transition from cyclosporine to methotrexate and experienced relief of their symptoms. Traditional treatment options for keratoacanthomas include standard excision, Mohs micrographic surgery, systemic retinoids, radiotherapy, curettage and electrodessication, and intralesional 5-fluorouracil.2 In patients with a predisposition to the development of pruritic nodules and multiple keratoacanthomas, many of the aforementioned treatments are ineffective or only elicit some clinical response, often with relapse.1 Intralesional methotrexate is noted in the literature as an effective and well-tolerated treatment for solitary keratoacanthomas.2, 3, 4 However, this approach may not be practical in the case of multiple keratoacanthomas, especially if it is believed that a predisposition exists for the development of additional lesions, as is the case in our patients.1 Systemic methotrexate, used for rheumatoid arthritis5 and psoriasis,6 has also been reported as an effective treatment for prurigo nodularis.7 Some literature supports the use of parenteral methotrexate as a method to ensure uniform and predictable bioavailability, particularly in doses at and greater than 15 mg.8, 9, 10, 11, 12 We have also observed that accessibility of injectable methotrexate is far more affordable than the oral tablet form, and patients are less likely to confuse their dosing regimens with the subcutaneous format. To our knowledge, there are no reports on the use of systemic methotrexate to treat keratoacanthomas. Three distinct cases are described in this report.