Congenital Milia En Plaque on Scalp

Abstract

Milia en plaque is a rare disease entity characterized by confluence of multiple keratin-filled cysts resulting from the obstruction of hair follicle without any preceding primary dermatosis. Fewer than 40 cases have been reported so far in dermatological literature, and most cases are described to occur in adults and in the peri-auricular area. We describe a case of congenital MEP on scalp of a five-year-old boy with a blaschkoid extension into posterior nuchal area. This case report claims its uniqueness because of the unusual site and congenital presentation.

What was known?

Primary milia en plaque is a rare clinical variant characterized by numerous tiny milia within an erythematous base that arise spontaneously on a healthy skin in a predisposed individual without any apparent causative factor. Pathogenesis behind this entity is unclear. Most cases are seen in adults and occur in peri-auricular areas.

Introduction

Milia en plaque (MEP) is a rare form of primary milia characterized by the presence of milia on an erythematous, edematous infiltrated plaque with or without comedones. The condition was first described by Balzer and Fouquet in 1903 and denominated by Hubler et al. in 1978.[1] Since then, less than 40 cases have been reported in literature till date.[2] MEP has been known to effect mostly peri-auricular and peri-orbital region in adults with a mean age of onset at 44 years with a slight female predilection.[1] We describe this unusual case of progressive milia en plaque on scalp in a five-year-old boy since birth, presenting with circumscribed cicatricial alopecia. This particular case claims its uniqueness because of its unusual site and congenital presentation. Presentation of MEP at birth gives new dimension to the existing hypothesized pathogenesis behind MEP.

Case Report

A five-year-old healthy boy presented to our outpatient department with a progressive, asymptomatic, circumscribed area of lost hair on the parietal scalp, studded with multiple tiny white, globoid, elevated lesions. The father gave history of this lesion being there since birth as a small area of alopecia with relative hardening of circumscribed scalp skin. Father denied any history suggestive of any long-standing pus-discharging infection, scaly dermatosis, or any preceding trauma at the site of the lesion. Over the last five years, the area of involvement increased in size and more such white elevated lesions appeared on the lesion and, despite treatment from multiple centers, there was no improvement. The boy was delivered by a normal vaginal delivery, and his parents had a non-consanguineous marriage. Nobody else in the family has similar lesions or any other significant history.

On examination, there was 5 × 6 cm² irregular, circumscribed erythematous and edematous plaque on the left parietal scalp, 6 cm above the mastoid tubercle. The surface of the plaque was devoid of hair and studded with multiple white milia of variable sizes [Figure 1a]. On needling one of the intact milia, white thick material was extruded from it, which was determined to be sterile after performing Gram stain. On palpation, there was no tenderness, induration, or increase in temperature. There were no comedones or any pustules or pus exudation on applying pressure over and around the lesion. There were areas of scarring and superficial crusting in few areas of the plaque. From the lower margin of the plaque, few discrete minute milia spread beyond the inferior margin of the original lesion, to be distributed in a linear fashion, extending up to the posterior nuchal area following a Blaschkoid pattern [Figure 1b]. However, bilateral retroauricular areas were spared of any milia. Potassium hydroxide (KOH) mount of hair uprooted from the margin of plaque did not reveal any fungal element.

Figure 1.

(a) Irregular, circumscribed erythematous, infiltrated plaque with complete alopecia and an uneven surface studded with multiple whitish globoid structures, on the left parietal scalp of a 5-year-old boy, (b) Same plaque showing a marginal extension of milia in a linear fashion along the posterior nuchal area following blaschkoid patten

Histopathology showed multiple keratin-filled inclusion cysts of variable sizes, lined by epithelia, interspersed between cross sections of hair adnexa in dermis with sparse lymphocytic infiltrates [Figure 2a, b, and c].

Figure 2.

(a) H and E, ×4 scanner view showing multiple cysts lined by epithelia and filled with strands of keratin, in the dermis, interspersed between cross sections of hair follicles with sparse inflammatory infiltrates, (b) H and E, ×10 view showing a cross sectional view of a keratin-filled milium adjacent to a hair follicle, which is in the process of giving rise to a milium, (c) H and E, ×40 view showing a closer view of one of the milia in the dermis, lined by epithelia and the keratin strands within

The child was started on minocycline 50 mg once daily, which he continued for three weeks without any considerable response. Oral isotretinoin 0.5 mg-1 mg/Kg od, for few weeks also failed to bring about any positive result. Parents did not consent for any surgical procedure.

Discussion

Milia are small keratin-filled cysts that result from the obstruction of a hair follicle or eccrine sweat ducts. Milia are classified as primary when their onset is spontaneous and secondary when they appear following trauma (such as burn, dermabrasion, ablative laser etc.), inflammatory skin diseases (particularly those involving the basement membrane zone, such as sub-epidermal bullous diseases), or the use of topical medication (topical corticosteroids, 5-fluorouracil) or systemic drugs (cyclosporine and benoxaprofen).[1,3] Primary milia en plaque is a rare clinical variant characterized by numerous tiny milia within an erythematous base that arise spontaneously on a healthy skin in a predisposed individual without any apparent causative factor.[1] Evidences show that primary milia originate in the hair follicle infundibulum, whereas the secondary forms may develop in various adnexal structures like sweat ducts, sebaceous glands, and hair follicle.[1,4] Despite being an asymptomatic benign lesion, MEP can be a major cosmetic concern to the patient. Earlier reports described this entity as a retroauricular dermatosis; however, later more case reports emerged with different sites of involvement like peri-orbital,[5] pre-auricular,[6] earlobes,[7] sub-mandibular area,[8] and supraclavicular area.[9] Though most cases of MEP have been described in adults, there were three case reports describing MEP in children aged 6 years, 10 years, and 14 years.[5,10,11]

The pathogenesis of MEP is unclear. Several theories have been hypothesized including trauma, cold environment, and underlying diseases such as discoid lupus erythematosus,[12] pseudoxanthoma elasticum,[13] follicular mucinosis, and mycosis fungoides.[14] All of these reports suggest some amount of antecedent tissue injury by the underlying diseases, which resulted in development of milia en plaque. Alteration in the infundibular portion of the follicle, resulting in dysfunctional keratinization and outlet obstruction or degeneration of elastic fibers are considered as various etiopathogenesis of MEP by some authors.[1] Presence of MEP at birth probably suggests intrauterine tissue alteration in that area, and extension of few milia along line of Blaschko's was probably due to migration of the altered tissue during cell line alignment in utero. A lack of positive family history, congenital presence, argues for a primary type of milia in our case.

There is no standard treatment for MEP, but there are reports of MEP being successfully treated by various medical as well as surgical treatments. Medical treatments of MEP include topical tretinoin,[1] oral isotretinoin,[14] etretinate,[2] minocycline,[7] photodynamic therapies,[1] producing variable response. Surgical modalities like simple extraction,[10,12] electrodessication,[11] dermabrasion,[15] and CO₂ laser evaporation[16] had been tried with variable success. Spontaneous regression has also been reported.[17]

Conclusion

MEP is a rare dermatological entity without any optimal treatments. Though most cases reported in the literature were of adult onset or childhood onset, presence of MEP at birth with a Blaschkoid extension in this case reports points towards an in-utero tissue insult. MEP in scalp presenting as a circumscribed area of cicatricial alopecia is also a unique feature of this case. Successful medical and surgical treatment still remains a challenge in this case with failed therapy with minocycline and isotretinoin.

What is new?

Scalp is a unique site of presentation for this entity. Though few cases of MEP with childhood onset have been described, congenital presentation of MEP on scalp with a Blaschkoid extension is unusual.