Continuing Education Activity

Milia are benign and transient subepidermal keratin cysts. These white appearing bumps are common, present in many different ways, and can develop in any area of the skin, most commonly the face. The lesions are seen in about half of full-term newborns, and due to a lack of clinical relevance, they are paid little to no attention. The natural course of milia is self-limited and, in most cases, will resolve without leaving a scar by one month of life. This activity reviews the evaluation and management of milia and highlights the role of the interprofessional team in evaluating and treating patients with this condition.

Objectives:

• Identify the etiology of milia.
• Describe the evaluation of milia.
• Review the management options available for milia.
• Collaborate with the interprofessional team to improve patient care.

Introduction

Milia (singular: milium) are benign and transient subepidermal keratin cysts that present as small, firm, white papules in various numbers, most commonly distributed on the face, but they can also be present on other anatomical areas such as the upper trunk, extremities, and genital area (prepuce). See Image. Milia, Face.

Milia classification includes primary and secondary. The vast majority of primary milia accounts for congenital milia that occur spontaneously and are present at birth, mainly over the nose, scalp, eyelids, cheeks, gum border (Bohn nodules), and palate (Epstein pearls). See Image. Milia, Mik Spots. Still, a small percentage of primary milia may occur in association with certain rare genodermatoses (inherited genetic skin disorders) in children and adults. Meanwhile, secondary milia manifest in association with underlying skin pathology, medications, or skin trauma.[1][2][3][4]

Etiology

Mainly, primary milia are considered to arise from the lower infundibular sebaceous collar of the vellus hair follicles; meanwhile, secondary milia are believed to derive more frequently from the eccrine ducts than from hair follicles, sebaceous ducts, or overlying epidermis.[5][6] The presence of primary milia is also linked to specific inherited genetic skin disorders (genodermatoses), including orofacial digital syndrome type 1, congenital hereditary trichodysplasia (Marie-Unna hypotrichosis), Basex-Dupre-Christol syndrome, and other ectodermal dysplasias. An uncommon presentation of primary milia, occurring on an erythematous plaque, is called milia en plaque; its etiology is still not well understood.[1][2][6] Secondary milia may arise after trauma, such as dermabrasion or radiotherapy. They also happen secondary to chronic topical steroid use with underlying atrophy and nonsteroidal anti-inflammatory drug use. Besides, they may manifest after the clearing of inflammatory skin diseases as sequelae of bullous disorders.[3][6]

Epidemiology

Primary congenital milia are so common that they could be considered a typical variation, occurring in up to 40% to 50% of healthy full-term neonates. However, milia may be delayed in premature neonates. Primary and secondary milia occur without significant racial or sex differences; only milia en plaque lesions are more common in females. Moreover, milia can affect persons of any age, but is most commonly seen in neonates with the congenital form.[2][7][8] 

Histopathology

In 1956, Epstein and Kligman described that "milia are probably the commonest benign tumors of the skin." Histopathologic studies support the notion that milia are not retention cysts but rather represent a simple, benign, keratinizing tumor. Histologically, primary congenital milia look like small cysts of the vellus hair follicles emerging at the level of the sebaceous duct and contain walls of several layers of thick stratified squamous epithelium with a granular cell layer, and in the center, contain keratinous material. On the other hand, secondary milia lesions present with the same histological characteristics as primary milia lesions. They may also derive from any epithelial structure, including parts of the pilosebaceous apparatus and eccrine glands, such as the epidermis, hair follicle, sebaceous duct, or sweat duct.[1][8][9]

History and Physical

Generally, the most common type (primary congenital milia) manifests at birth, but its onset in premature newborns could manifest weeks later. Milia lesions are commonly asymptomatic and resolves spontaneously during the first months of life. However, clinical information may vary depending on the milia subtype. When acquired (secondary milia), it usually affects older children, and a previous history of trauma or bullous skin disease could be present. This type of milia may persist without treatment. 

Classification of Milia

Primary milia

• Congenital
• Benign primary milia of children and adults
• Milia en plaque
• Nodular grouped milia
• Multiple eruptive milia 
• Nevus depigmentosus with milia
• Genodermatosis-associated

Secondary milia

• Disease-associated
• Medication-associated 
• Trauma-associated 

Physical Examination

Congenital milia usually arise spontaneously and present as small, white-to-yellow, smooth, dome-shaped papules measuring less than 3 mm; in darker skin, they may show a subtle blue tint. These lesions can appear singly or in clusters, most often on the face, with the nose commonly affected. Benign acquired milia, which also develop spontaneously, tend to occur on the eyelids, cheeks, forehead, and genitalia. Milia en plaque presents differently, showing an erythematous plaque studded with numerous milia that may span several centimeters. Another pattern, acquired widespread multiple eruptive milia, emerges suddenly over weeks to months and typically occurs sporadically. However, it can be inherited in an autosomal dominant fashion or appear with certain genodermatoses. Milia have been reported in association with conditions such as Brooke-Spiegler syndrome, pachyonychia congenita type 2, and basal cell nevus syndrome. They may also develop alongside blistering disorders like porphyria cutanea tarda or epidermolysis bullosa. Medication-related cases appear with chronic topical steroid use in atrophic skin or with nonsteroidal anti-inflammatory drugs. Secondary traumatic milia most often follow burns, skin grafting, dermabrasion, or radiotherapy.[1][2][5]

Evaluation

Milia lesions are diagnosed on clinical findings. Although seldom required, incision and drainage of the keratinous content of milia can corroborate the diagnosis. Additionally, persistent and widely distributed milia may require investigation for other causes of primary and secondary milia, such as an underlying genodermatosis, especially when other clinical findings are present.[5][8]

Treatment / Management

The lesions of congenital milia do not require specific treatment, as they tend to resolve spontaneously. The other forms of primary milia, along with secondary milia, may not resolve on their own and can be treated with simple surgical interventions such as evacuation with a tiny incision and tangential pressure applied with a comedone extractor or curette. Other treatment options for multiple milia include topical retinoids and electrodesiccation or electrocautery.[5][8]

Differential Diagnosis

The principal differential diagnosis is sebaceous hyperplasia, which presents as white-to-yellow, grouped papules around the upper lip and nose. Similarly to congenital milia, sebaceous hyperplasia is less frequent in premature newborns. Other differential diagnoses could include comedonal acne, flat warts, and milia-like idiopathic calcinosis cutis.[5]

Prognosis

Congenital milia tend to resolve spontaneously without scarring within a couple of weeks, though they may persist for several months, usually disappearing during the first month of life. Acquired milia may continue without treatment.[2][5][10]

Complications

No systemic complications have been documented. Milia are benign and asymptomatic lesions.[5]

Deterrence and Patient Education

Practitioners should educate caregivers about the benign course of milia and its spontaneous resolution without scarring.

Enhancing Healthcare Team Outcomes

Healthcare workers need to be aware that milia are benign, transient dermal cysts of keratin that can occur in various areas of the skin, most commonly the face (nose, gums, and palate). Although these lesions are often seen in about half of full-term newborns, they receive little attention. The natural course of milia is self-limited and, in most cases, resolves without scarring within 1 month of life. However, if present in older children, they could be associated with an underlying inherited skin disorder or be secondary to skin trauma. Thus, in older age groups, these possible etiologies may need to be considered by physicians and nurses based on other historical and clinical findings to improve outcomes. But when in doubt about the diagnosis, the patient should be referred to dermatology. Finally, neonatologists, primary care providers, and nursing staff working in nurseries should provide education to caregivers and their families about this skin condition to improve patient-centered care.

Review Questions

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References

1.

Honda Y, Egawa K, Baba Y, Ono T. Sweat duct milia--immunohistological analysis of structure and three-dimensional reconstruction. Arch Dermatol Res. 1996 Mar;288(3):133-9. [PubMed: 8967781]

2.

Rutter KJ, Judge MR. Profuse congenital milia in a family. Pediatr Dermatol. 2009 Jan-Feb;26(1):62-4. [PubMed: 19250409]

3.

Langley RG, Walsh NM, Ross JB. Multiple eruptive milia: report of a case, review of the literature, and a classification. J Am Acad Dermatol. 1997 Aug;37(2 Pt 2):353-6. [PubMed: 9270547]

4.

Rayala BZ, Morrell DS. Common Skin Conditions in Children: Neonatal Skin Lesions. FP Essent. 2017 Feb;453:11-17. [PubMed: 28196316]

5.

Berk DR, Bayliss SJ. Milia: a review and classification. J Am Acad Dermatol. 2008 Dec;59(6):1050-63. [PubMed: 18819726]

6.

Kurokawa I, Kakuno A, Tsubura A. Milia may originate from the outermost layers of the hair bulge of the outer root sheath: A case report. Oncol Lett. 2016 Dec;12(6):5190-5192. [PMC free article: PMC5228532] [PubMed: 28105227]

7.

Haveri FT, Inamadar AC. A cross-sectional prospective study of cutaneous lesions in newborn. ISRN Dermatol. 2014;2014:360590. [PMC free article: PMC3918370] [PubMed: 24575304]

8.

Kutlubay Z, Tanakol A, Engýn B, Onel C, Sýmsek E, Serdaroglu S, Tuzun Y, Yilmaz E, Eren B. Newborn Skin: Common Skin Problems. Maedica (Bucur). 2017 Jan;12(1):42-47. [PMC free article: PMC5574071] [PubMed: 28878836]

9.

EPSTEIN W, KLIGMAN AM. The pathogenesis of milia and benign tumors of the skin. J Invest Dermatol. 1956 Jan;26(1):1-11. [PubMed: 13295633]

10.

Nakai N, Okuzawa Y, Katoh N, Kishimoto S. Persistent congenital milia involving the skin of the whole body in an infant with trisomy 13 syndrome. Pediatr Dermatol. 2010 Nov-Dec;27(6):657-8. [PubMed: 21510019]

Disclosure: Patricio Gallardo Avila declares no relevant financial relationships with ineligible companies.

Disclosure: Magda Mendez declares no relevant financial relationships with ineligible companies.