Kyrle's disease.

A 7-year-old female presented with complaints of raised dark-colored lesions on extremities since 3 years of age. On examination, she had multiple well-defined discrete hyperpigmented keratotic papulo-nodular lesions with crusted crateriform center seen on extensor surface of upper and lower extremities with multiple well-defined hypo-hyperpigmented macules on the back.

A 45-year-old female presented with complaints of dark-colored lesion on both hands, feet, trunk and buttocks since 2 years. She was a known case of diabetes mellitus since 6 years and was taking insulin. On examination, she had multiple hyperpigmented papules with central keratotic plug seen over buttocks, hands and feet with hyperpigmented macules and papules [Figure 1].

Figure 1

Multiple hyperpigmented plaques with central keratotic plugs on the leg of a 45-year-old woman

A biopsy done in both cases showed a shallow extra-follicular cup-shaped epidermal invagination filled with compact orthokeratosis [Figure 2]. There were dyskeratotic keratinocytes going up to the basal layer [Figure 3]. The epidermis showed irregular hyperplasia and acanthosis. There was dense lympho-histiocytic infiltrate in the upper dermis. Special stains were done to rule out other perforating disorders. Elastic Von Geison stain did not reveal elastic fibers. Masson trichrome was negative for collagen fibers.

Figure 2

Photomicrograph showing shallow extra-follicular cup-shaped epidermal invagination filled with compact orthokeratosis, dermis showing dense inflammatory infiltrate [H and E, ×4]

Figure 3

Photomicrograph showing dyskeratotic keratinocytes going up to the basal layer [H and E,×400]

Kyrle's disease was first described in 1916 by Kyrle as “hyperkeratosis follicularis et follicularis in cutem penetrans.”[1] Two distinct forms exist: an inherited form that presents in childhood and an acquired form that usually develops in adulthood, more commonly in women between 30 and 50 years of age[2] associated with underlying systemic disorders like chronic renal failure, diabetes, prurigo nodularis and even keratosis pilaris.

The primary event is claimed to be a disturbance of epidermal keratinization characterized by the formation of dyskeratotic foci and acceleration of the process of keratinization.[1] This rapid production of abnormal keratin results in the formation of an overlying parakeratotic column, which perforates into the dermis, eliciting a granulomatous inflammatory reaction[12] Subsequent re-epithelialization from the adjacent epidermis covers this entire process from the base. The dermal connective tissue, inflammation and the keratotic debris degenerate to form the basophilic debris, which corresponds to the keratotic plug.[2] This is exuded from the invagination seen in the fully evolved form of the lesion.

Kyrle's disease should be differentiated from other primary perforating dermatosis. In perforating folliculitis, the epidermal invagination is seen in relation to a vellus hair, which were absent in our cases. In elastosis perforans serpiginosa, there are thickened elastic fibers around epidermal invagination. Reactive perforating collagenosis was also ruled out due to the lack of degenerated collagen at the base of the perforation.