Multiple keratoacanthomas developing in healing plaques of Psoriasis
A 22-year-old male patient presented with multiple reddish raised scaly lesions all over his body associated with scaling over the scalp for one year. The patient was shopkeeper by profession dealing in stationary items, there was no history of smoking or tobacco intake. Patient had skin type V, and there was no history of diabetes, tuberculosis, or any other immunosuppressive disease. He had applied various emollients and topical steroids with no lasting relief; however, there was no history of tar application or phototherapy. Clinical examination revealed multiple well-circumscribed erythematous indurated scaly plaques on the scalp, bilateral upper and lower limbs, back, and on buttocks. Auspitz sign was positive over the lesions. The diagnosis of psoriasis vulgaris was confirmed by histopathological examination. The Psoriasis Area and Severity Index (PASI) was estimated to be 26.2. After hematological and biochemical investigations, X-ray chest and HIV test, the patient was started on oral methotrexate 15 mg weekly. He significantly improved on this dose, and PASI dropped to 11.5 after three months. The dose was decreased to 7.5 mg weekly, and the patient was maintained on this dose and kept under monthly follow-up.\nFour months later, the patient presented with reddish to hyperpigmented raised nodules over the healing lesions of psoriasis. The nodules were firm and almost all had a central crater.\nHe also reported self resolution of few of the lesions over a period of 6 to 12 weeks without any specific treatment. Examination revealed the presence of multiple well defined dome shaped erythematous to hyperpigmented nodules, ranging in size from 5 to 15 mm, over both legs, especially shins, and a few over the arms and forearms []. The lesions were present on sun exposed as well as on non exposed areas. The nodules were characteristically present over the healing plaques of psoriasis vulgaris. Few post inflammatory hyperpigmented macules and atrophic scars were seen at the sites where previous nodules had healed spontaneously.\nHistopathological examination of the nodules showed a globular growth having a central crater containing keratinous material. The epidermis surrounding the crater was acanthotic and overlapped the crater laterally (“lipping”). Keratinocytes formed islands and cords and had pale eosinophilic cytoplasm []. These features were consistent with keratoacanthoma, and a diagnosis of multiple keratoacanthomas was made.\nThe patient was unwilling to opt for any therapy for the keratoacanthomas in view of spontaneous resolution of few of them. Weekly methotrexate was continued for control of psoriasis. The patient was followed up for the next 6 months, during which time keratoacanthomas continued to appear and some resolved leaving behind scarring. The patient was asked to apply tazarotene gel 0.1% daily over the residual lesions.