Milia: A review and classification

doi:10.1016/j.jaad.2008.07.034

Journal of the American Academy of Dermatology

Volume 59, Issue 6, December 2008, Pages 1050-1063

https://doi.org/10.1016/j.jaad.2008.07.034 Get rights and content

Milia are frequently encountered as a primary or secondary patient concern in pediatric and adult clinics, and in general or surgical dermatology practice. Nevertheless, there are few studies on the origin of milia and, to our knowledge, there is no previous comprehensive review of the subject. We review the various forms of milia, highlighting rare variants including genodermatosis-associated milia, and present an updated classification.

Section snippets

Origin

Few studies have investigated the origin of milia.3, 4, 5, 6 In general, primary milia are thought to originate from the sebaceous collar of vellus hairs (lower infundibulum), whereas secondary milia are believed to derive from eccrine ducts more commonly than from overlying epidermis, hair follicles, or sebaceous ducts.

Epstein and Kligman³ performed serial sectioning of 4 types of milia: primary milia and secondary milia caused by epidermolysis bullosa (EB), dermabrasion, and experimental

Congenital milia

Congenital milia occur in 40% to 50% of newborns, favoring the face (especially the nose), scalp, upper aspect of trunk, and upper extremities, without significant racial or sex difference (Fig 2).7, 8, 9, 10, 11, 12, 13 Congenital milia present with a few or numerous lesions and tend to resolve spontaneously within weeks to several months. Milia may be less common and of delayed onset in premature newborns.¹² The main differential diagnosis is sebaceous hyperplasia, which appears as follicular

Genodermatoses with milia

Milia may be a major or minor feature of many genodermatoses (Table II).

Secondary milia

Secondary milia represent a localized form of milia that may be disease associated, medication associated, or caused by trauma. Secondary milia may resolve spontaneously but tend to persist. Postbullous (particularly subepidermal) milia are the classic disease-associated type.¹⁴⁷ EB and porphyria cutanea tarda are typical examples. Other diseases reported with secondary milia include bullous pemphigoid, herpes zoster,¹⁴⁸ contact dermatitis,¹⁴⁹ bullous lupus erythematosus,¹⁵⁰ Sweet syndrome,¹⁵¹

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Benign tumors of the eye and eyelid are common in children and adults, and they rarely undergo malignant transformation. Their workup and management have evolved over the years with increasing advancements in surgical and laser therapies. This contribution focuses on describing the following benign eye and eyelid tumors and their diagnostic and treatment approaches: congenital and acquired melanocytic nevi; nevus of Ota (Hori nevus); conjunctival papilloma; seborrheic keratosis; epidermoid cyst; dermoid cyst; milium; xanthelasma; hemangioma (cherry angioma and pyogenic granuloma); neurofibroma; neurilemmoma (schwannoma); and fibroepithelial polyp. Surgical removal is the primary treatment approach for many of these benign tumors. With advancements in laser technologies, there are now several laser types that can be used in the treatment of these benign eye and eyelid tumors. Other treatment modalities include cryosurgery, electrosurgery, and topical or intralesional medications. We hope this review will provide a reference to dermatologists and ophthalmologists in their approach to evaluation and management of benign eye and eyelid tumors.
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The fetal and neonatal skin gradually matures with gestational age with changes both in structure and barrier function. There are measurable improvements in temperature homeostasis and transcutaneous water losses. This chapter describes the physiologic maturation of the skin during the peri- and neonatal period, congenital disorders of skin structure, inflammatory conditions, scaling abnormalities, skin infections, and cutaneous neoplasms. The information is summarized from our own clinical experience and from information mined from PubMed, Embase, and Scopus.
Importance of the transient benign cutaneous lesions in the newborn and their differential diagnosis
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Multiple milia formation in blistering diseases
2020, International Journal of Women's Dermatology
Milia are superficial keratinous cysts seen as pearly white, dome-shaped lesions 1–2 mm in diameter. Milia are associated with diseases that cause subepidermal blistering, such as hereditary forms of epidermolysis bullosa, epidermolysis bullosa acquisita, bullous pemphigoid, bullous lichen planus, and porphyria cutanea tarda. Multiple eruptive milia are rare and more extensive in number than primary milia.
The aim of this study was to search the literature for cases of blistering diseases with multiple milia formation, especially in areas of the skin where there was no evidence of blistering or trauma, and review the interpretations of their pathogenesis.
We performed a literature search with the terms multiple milia and bullous diseases, pemphigoid, and pemphigus.
Very few studies have investigated the origin of milia. Primary milia are thought to originate from the sebaceous collar of vellus hairs, and secondary milia are believed to derive from eccrine ducts more commonly than from overlying epidermis, hair follicles, or sebaceous ducts. Milia secondary to blisters or trauma are speculated to be produced through the regeneration process of disrupted sweat glands or hair follicles. Immunological predisposition, aberrant interaction between the hemidesmosomes, and the extracellular matrix components beneath the hemidesmosomes have been described with regard to the formation of numerous milia during recovery. Multiple milia could be a primary manifestation of dystrophic epidermolysis bullosa in skin areas without evidence of blistering.
The exact etiology of multiple milia remains unknown. Immunological predisposition and improper interaction between hemidesmosomes and extracellular matrix components are speculated to play a role in the formation of milia during recovery of bullous lesions in blistering diseases. Still, further studies on the triggering mechanisms of keratinocyte dysfunction in cases of multiple milia formation without evidence of prior blistering are needed.
Eruptive milia and acneiform hyperkeratosis with comedones (pseudo-epidermal cysts) within tattoos
2019, Annales de Dermatologie et de Venereologie
Milia are small, hard, white superficial epidermal cysts measuring a few millimetres that can occur during skin healing due to occlusion of pilosebaceous units. Milia rarely occur on tattoos. However, cases of allergic reactions with hyperkeratosis and open comedones have been described in the literature, sometimes under the term “epidermal cysts”.
We saw three patients who developed milia, including a 32-year-old man with eruptive milia 10 weeks after getting a black, red and green tattoo on his upper arm. Topical tretinoin was applied. We encountered two further cases of eruptive milia on black/grey tattoos. A fourth patient presented a massive hyperkeratotic reaction with retention comedones on the red/pink area of a tattoo.
The occurrence of milia and acneiform allergic reactions after tattooing is rare. We collated a total of 13 cases from the literature, of which 8 involved milia. This condition occurred within 3 months following tattooing, with no particular correlation with any given colour, and generally without any allergic reaction (except in one case). Reactions comprising excessive acneiform hyperkeratosis and open comedones were noted with pink and red inks and were a complication in a setting of allergic inflammatory reaction. However, the histopathology of these reactions is poorly described in the literature. It seems inappropriate to diagnose the condition as “epidermal cysts” since the lesions are not in fact simple cysts but rather retention lesions occurring during an inflammatory reaction and are thus different from post-traumatic milia.
Les grains de milium (GM) sont des petites papules cutanées superficielles, blanches, perlées et dures, qui correspondent à des kystes épidermiques. Ils peuvent être secondaires, notamment par obturation du follicule pilosébacé lors de processus de cicatrisation. La survenue de GM après tatouage est rare. Par ailleurs, des cas de réactions allergiques sur tatouage avec une importante hyperkératose parsemée de comédons ouverts ont également été décrits dans la littérature, parfois étiquetés « kystes épidermiques ».
Nous avons rencontré trois patients qui avaient développé des GM post-tatouage, notamment un homme de 32 ans qui a présenté une éruption de GM sur toutes les couleurs (noir, rouge, vert) d’un tatouage effectué plus de deux mois et demi auparavant. Un traitement par trétinoïne topique était proposé. Par ailleurs, nous avons vu un cas de réaction d’hyperkératose massive avec comédons par rétention sur le rouge/rose d’un tatouage.
La survenue de GM et de réactions acnéiformes avec comédons sur tatouage est rare. Nous avons colligé au total 13 cas de la littérature, dont 8 GM. Les GM surviennent sans affinité spécifique pour une couleur de pigment, dans les 3 premiers mois après le tatouage, en dehors de toute réaction allergique (hormis un cas). À l’opposé, les réactions d’hyperkératose excessive accompagnée de comédons par rétention sont observées sur le rouge/rose et semblent compliquer une réaction inflammatoire allergique. Sur le plan histopathologique, ces réactions sont rarement décrites avec précision dans la littérature. Mais le terme de « kystes épidermiques », parfois employé, nous semble inapproprié pour décrire ces lésions, car il ne s’agit pas de kystes simples mais de lésions rétentionnelles survenant dans le cadre d’une réaction inflammatoire.

View all citing articles on Scopus

: Funding sources: None.

: Conflicts of interest: None declared.

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ReviewMilia: A review and classification

Section snippets

Origin

Congenital milia

Genodermatoses with milia

Secondary milia

J Invest Dermatol

J Invest Dermatol

J Am Acad Dermatol

J Am Acad Dermatol

J Am Acad Dermatol

J Am Acad Dermatol

J Am Acad Dermatol

Ann Dermatol Venereol

J Am Acad Dermatol

J Invest Dermatol

J Invest Dermatol

Genomics

J Invest Dermatol

J Invest Dermatol

J Invest Dermatol

J Investig Dermatol Symp Proc

J Am Acad Dermatol

Milia en plaque

Cutis

Eruptive milia

Cutis

Sweat duct milia–immunohistological analysis of structure and three-dimensional reconstruction

Arch Dermatol Res

An investigation of cytokeratin expression in skin epithelial cysts and some uncommon types of cystic tumors using chain-specific antibodies

Arch Dermatol Res

Survey of cutaneous lesions in Indian newborns

Pediatr Dermatol

Birthmarks in 4346 Finnish newborns

Acta Derm Venereol

Statistical survey of skin changes in Japanese neonates

Pediatr Dermatol

Skin changes in newborn infants in the first 5 days of life [German]

Hautarzt

Cutaneous lesions in newborn

Indian J Dermatol Venereol Leprol

One-year survey of cutaneous lesions in 1000 consecutive Iranian newborns

Pediatr Dermatol

Bohn's nodules

Int J Dermatol

Comparison of palatal and alveolar cysts of the newborn in premature and full-term infants

Pediatr Dent

Oral and facial inclusion cysts in newborns

J Clin Pediatr Dent

Oral findings in a group of newborn Swedish children

Int J Paediatr Dent

The “nasal crease”: a physical sign of allergic rhinitis

JAMA

Familial transverse nasal groove

Arch Dermatol

Congenital milia in the nasal groove

Br J Dermatol

Milia cysts along the nasal groove in a child

Clin Exp Dermatol

Pseudoacne of the nasal crease: a new entity?

Pediatr Dermatol

Multiple milia localized to the vulva

J Dermatol

A case of multiple milia occurring on the vulva

Korean J Dermatol

Persistent congenital milia with nevus spilus

Indian J Dermatol Venereol Leprol

Retroauricular dermatitis of the “milia en plaque” type [French]

Ann Dermatol Venereol

Retroauricular bilateral 'milia en plaque

Dermatology

Milia en plaque–a new site and novel treatment

Clin Exp Dermatol

Milia en plaque

Br J Dermatol

Milia en plaque associated with pseudoxanthoma elasticum

J Cutan Pathol

Milia en plaque of the eyelids in childhood: case report and review of the literature

Pediatr Dermatol

Milia en plaque

Review
Milia: A review and classification