Milia

Milia (singular milium) are tiny, superficial, keratin filled epidermal cysts, 1 to 2 mm in size, lined by stratified squamous epithelium. They arise from the pilosebaceous unit of vellus hair follicles, from sweat ducts, or from the epidermis after injury.

• Primary milia:
  • Neonatal milia: in 40 to 50% of newborns, on the face and nose, resolving in 2 to 4 weeks. Epstein pearls (on the palate) and Bohn nodules (on the gums) are similar.
  • Benign primary milia in children and adults: on the eyelids, cheeks and forehead.
  • Milia en plaque: milia on an erythematous plaque, usually behind the ear or on the eyelid.
  • Nodular grouped milia and multiple eruptive milia.
  • Genetic: Bazex-Dupre-Christol syndrome, Rombo syndrome, oro-facial-digital syndrome type 1, pachyonychia congenita type 2, and Brooke-Spiegler syndrome.
• Secondary milia: follow blistering (epidermolysis bullosa, porphyria cutanea tarda, bullous pemphigoid, burns), trauma, dermabrasion, laser resurfacing, radiotherapy, prolonged topical corticosteroid use, topical fluorouracil, contact dermatitis, and chronic sun damage. They occur as the epidermis heals over trapped adnexal structures.
• Benign, and not infectious.

• Firm, white to yellowish, dome shaped papules, 1 to 3 mm, with a smooth surface and no central punctum (unlike comedones). Seen mainly on the eyelids, cheeks, nose and forehead.
• Not inflamed and asymptomatic. Eruptive forms involve many lesions on the trunk and limbs.
• In secondary milia the lesions appear in the area of the earlier blister or injury, weeks later.
• Differential diagnosis: sebaceous hyperplasia (yellow, umbilicated), syringoma (skin coloured papules on the lower eyelids), closed comedones, molluscum contagiosum (umbilicated), xanthelasma, steatocystoma, trichoepithelioma, basal cell carcinoma (milia like pearly papule), epidermoid cysts, warts, and calcinosis cutis.
• Red flags: milia with blistering on sun exposed skin, skin fragility, and dark urine (porphyria cutanea tarda), or with hair loss, scarring, nail changes, or dental problems (genetic disorders).
• Complications: cosmetic concern, and rare inflammation if squeezed.

• Clinical. The firm white papule without a punctum on the face, with a history of injury or blistering for secondary lesions.
• Dermoscopy shows a round white to yellowish structure. Biopsy is rarely needed, and shows a keratin filled cyst with a granular layer.
• If milia follow blistering on exposed skin, check plasma and urine porphyrins, liver tests, iron studies, hepatitis C, HIV and glucose (porphyria cutanea tarda). In a child with inherited blistering, refer to a specialist centre with biopsy for immunofluorescence mapping.
• Genetic referral where a syndrome is suspected.

• Neonatal milia: reassure parents. They resolve by themselves in 2 to 4 weeks. Do not squeeze, scrub or apply creams and oils.
• Milia in children and adults can persist for months to years, and often resolve without treatment. Treatment is cosmetic:
  • Extraction (the most effective): after cleaning with an antiseptic (chlorhexidine 2% or alcohol), make a tiny nick in the surface with a sterile 21 gauge needle or number 11 blade, and press out the white core with a comedone extractor. No anaesthesia is usually needed. Do not squeeze without incising, as this causes bruising and scarring.
  • Topical retinoids: tretinoin 0.025 to 0.05% cream or adapalene 0.1% gel nightly for 8 to 12 weeks, to promote exfoliation and prevent new lesions.
  • Azelaic acid 15 to 20% twice daily, or chemical peels (salicylic acid 20 to 30% or glycolic acid 30 to 50%) every 2 to 4 weeks for 3 to 6 sessions.
  • Light electrodesiccation, curettage or carbon dioxide laser for multiple lesions, with a risk of scarring and pigment change.
  • Microdermabrasion for mild disease.
• Treat or remove the cause of secondary milia: stop long term topical steroids and occlusive products, protect from the sun, and treat the underlying blistering disease or porphyria (avoid alcohol and oestrogens, repeated phlebotomy, or hydroxychloroquine 100 mg twice weekly, under specialist care).
• Milia en plaque and multiple eruptive milia: extraction plus topical retinoid. Oral therapy (minocycline 100 mg twice daily or isotretinoin) is used rarely in extensive disease, with limited evidence.
• Special groups:
  • Infants: no treatment.
  • Pregnancy: avoid retinoids and salicylic acid peels. Extraction and azelaic acid are acceptable.
  • Dark skin: avoid aggressive peels and lasers, which cause pigmentation.
  • Periocular milia: extraction only by an experienced clinician, or referral to ophthalmology.
• Follow up: not needed for primary milia. Review at 8 to 12 weeks after retinoid therapy. Refer to dermatology for extensive or syndromic disease, suspected porphyria, or diagnostic uncertainty.