Psoriasis vulgaris with fibrokeratoma from pityriasis amiantacea.

Introduction

Pityriasis amiantacea is a rare clinical condition characterized by masses of waxy and sticky scales that adhere to the scalp and tenaciously attach to hair bundles.1, 2 Pityriasis amiantacea can be associated with psoriasis vulgaris (PsV). We examined a patient with pityriasis amiantacea caused by PsV who also had keratotic horns on the scalp, histopathologically fibrokeratomas. To the best of our knowledge, this is the first case of scalp fibrokeratoma stimulated by pityriasis amiantacea and PsV.

Case report

A 54-year-old Japanese man with a 35-year history of severe PsV presented to our hospital. He had been treated with a topical steroid and phototherapy but had discontinued all treatments 1 year prior to presenting to our hospital.

On physical examination, he was found to have well-circumscribed erythematous patches and plaques with silvery-white scales on the entire body. Joint pain was present, but it was limited to the hands and right knee. Moreover, he presented with sticky, silvery scales adhering to the scalp and agglutinating the hair shafts (Fig 1, A). We diagnosed this characteristic clinical feature as pityriasis amiantacea associated with PsV. When we removed the scales gently using olive oil, surprisingly, about 50 horns each 1 mm in diameter and 5 mm in length were found scattered on the PsV lesions (Fig 1, B). These horns were distinctively keratinized at the top and showed marked surface telangiectasia under dermoscopy.

Fig 1

A, Sticky, silvery scales adhering to the scalp and agglutinating the shafts of the hairs. B, Distinctive horns that were keratinized at the top were present on the scalp. C, Hyperkeratosis, dermal fibrosis, and dilated vessels in the papillary dermis. (C, Hematoxylin-eosin stain; original magnifications: upper, ×10; lower, ×200.)

A biopsy specimen revealed hyperkeratosis, dermal fibrosis, and dilated vessels in the papillary dermis (Fig 1, C). We diagnosed these horns as fibrokeratomas.

The scalp PsV lesions were treated with topical corticosteroid, and the keratotic horns were removed by the patient with scissors. Although a few PsV plaques appeared temporarily, there has been no recurrence of pityriasis amiantacea or fibrokeratomas in the last 2 years.

Discussion

Pityriasis amiantacea is an unusual condition characterized by masses of waxy, sticky, silvery scales that adhere to the scalp and attach to hair bundles.1, 2 The specific cause remains unclear, although pityriasis amiantacea is associated with various inflammatory scalp diseases, including psoriasis, streptococcal and fungal infections, pyoderma, seborrheic dermatitis, and atopic dermatits.

In the present case, peculiar and striking keratotic horns were observed on the scalp under pityriasis amiantacea lesions, and they were pathologically fibrokeratomas. To the best of our knowledge, fibrokeratomas on the scalp have never been reported.

Because the patient had severe PsV over his whole body and the pityriasis amiantacea lesions were associated with PsV, we speculate that repeated mechanical stimuli and minor trauma played a significant role in the fibrokeratoma formation, similar to Köbner phenomenon. The patient had been picking at the scales on the scalp to remove them over the course of a year, and trauma is generally regarded as a predisposing factor for fibrokeratomas, such as it is in Koenen tumors of tuberous sclerosis. In light of the patient's behavior, it is possible that repeated pulling and rubbing of the scalp caused the fibrokeratomas to form beneath the pityriasis amiantacea, especially given the background of PsV. The pityriasis amiantacea had recurred several times. Moreover, the patient had left the psoriatic lesions untreated over the course of 1 year. The patient's decision to not treat PsV in combination with picking the lesions might have caused this rare, strange clinical feature.

In this case, the fibrokeratomas were cut with scissors by the patient. Usually, the treatment for a fibrokeratoma is a local excision. However, if there are many lesions, as in this case, cryotherapy or CO2 laser therapy should be considered.

In conclusion, we described the first case of scalp fibrokeratomas in a PsV patient. Thick scalp scales clinically manifesting as pityriasis amiantacea might have played a part in forming such striking skin lesions. We should keep in mind the onset of fibrokeratomas as a rare complication of psoriasis.