Nevus comedonicus on scalp: a rare site.

Nevus comedonicus is rare hamartoma of the pilosebaceous unit. Curiously the scalp is rarely involved. Here we are reporting 33-year-old male presenting with nevus comedonicus arranged linearly on the scalp. There was positive family history of similar lesion on the similar site. This case has been presented for its sheer rarity and atypical site.

What was known?

Nevus comedonicus is rare hamartoma of the pilosebaceous unit.

Introduction

Comedo nevus also known as nevus comedonicus is a rare nevus. It is a linear lesion comprising numerous keratin-filled pits, sometimes with acneiform pustules. The commonest site is the face, followed by the neck, trunk and upper arm. Palms, soles and the glans penis, from which pilosebaceous follicles are normally absent, may occasionally be involved. Curiously the scalp is rarely involved.[1]

Case Report

A 33-year-old male patient presented to our department with groups of discrete pits filled with keratin resembling comedones over his scalp. The lesions were present since birth and gradually increasing in size not associated with itching. History of similar lesion was present in his grandparent. There was no history of suppuration, discharge or inflammation on the lesions. There was no history suggestive of involvement of central nervous system, skeletal and ocular involvement. There was no other similar lesion elsewhere in the body.

Cutaneous examination revealed multiple dilated follicular openings filled with black plugs over the scalp arranged linearly. There was normal skin in between the two groups [Figure 1]. Routine hematological examination is within normal limits. A punch biopsy was done from the lesion. Histopathology showed epidermis with deep invagination filled with keratin [Figure 2]. The dermis showed rudimentary appendages.

Figure 1

Multiple keratin filled pits present on the scalp with intervening normal skin

Figure 2

Histopathology showing epidermis with deep invagination filled with keratin; H and E 40x

Based on the clinical characteristics and histopathology findings a diagnosis of nevus comedonicus was made. The patient was started on topical retinoids and currently lost for follow up.

Discussion

Naevus comedonicus is a rare hamartoma of the pilosebaceous unit.[2] It was first described by Kofmann in 1895.[3] Comedo naevus on hair-bearing limbs contiguous with lesions involving eccrine ducts on the palms and soles, resembling porokeratotic eccrine ostial and dermal duct nevus, and glans penis, supports a non-appendage-specific epidermal problem causing duct blockage.[1] Clinically, it presents as comedo like dilated pores with keratinaceous plugs in a linear, nevoid, bilateral or zosteriform pattern. The intervening epidermis may appear normal, hyperkeratotic, or slightly hypo- or hyperpigmented. In the inflammatory variant, there will be suppurative cysts and acne like lesions.[12] In our patient, there were two groups of comedo like pores arranged linearly with intervening normal skin. There were no signs of inflammation.

Nevus comedonicus syndrome is the association of nevus comedonicus with non-cutaneous findings such as skeletal defects, cerebral abnormalities, and cataracts.[2] Detailed examination of our patient did not reveal any other abnormalities.

The scalp is very rare site for the naevus comedonicus. There are very few reports of comedo naevus affecting scalp. Ghaninezhad et al.,[4] reported nevus comedonicus on the scalp in a 3-year-old boy. There were no other physical or cutaneous abnormalities in that patient. There was no family history of similar lesions. Sikorski et al., reported another case of nevus comedonicus on the scalp in 16 month old male child, who presented with intermittent “discharge” on the lesion.[5]

Treatment of comedo naevus includes surgical excision with tissue expansion which is more effective in the long term than superficial shaving or dermabrasion. Topical retinoic acid and 12% ammonium lactate may be used. Tacalcitol and tazarotene 0.05% with calcipotriene 0.005% daily have also been used effectively.[1]

In conclusion, we are presenting a case of linear nevus comedonicus on scalp. This rare case has been presented for its classical presentation and affection of rare site.

What is new?

Nevus comedonicus affecting scalp.