Milium (milia) is a small epidermal cyst containing keratin, which typically occurs in newborns and can also develop in certain dermatoses and after trauma. The ICD-10 code is L72.8.
Milia can occur in all ages and races, but is most commonly observed in newborns. Milia may also occur in certain dermatoses, inherited disorders, and after trauma (see Classification). Milia develop when the protein keratin gets trapped under the skin.
Classification:
Primary Milia:
- Congenital Milia (present at birth)
- Benign Primary Milia in children, adolescents, and adults
- Milia en plaque
- Grouped nodular milia
- Multiple eruptive milia
- Depigmented nevus with milia
- Milia associated with inherited disorders:
- Bazex-Dupré-Christol syndrome
- Rombo syndrome
- Brooke-Spiegler syndrome
- Atrichia with papular lesions
- Vitamin D-dependent rickets type IIA
- Basal cell nevus syndrome
- Generalized basaloid follicular hamartoma syndrome
- Absence of fingerprints-congenital milia syndrome (Baird syndrome)
- Nicolau-Balus syndrome
- Hypotrichosis with juvenile macular dystrophy
- KID syndrome
- Loeys-Dietz syndrome.
Secondary Milia:
- Post-traumatic (on sites of abrasions, sunburns, postoperative wounds, dermatoses, cryotherapy)
- Milia associated with dermatoses (porphyria cutanea tarda, bullous epidermolysis, bullous pemphigoid, herpes zoster, dermatitis herpetiformis, discoid lupus erythematosus, lichen sclerosis, lichen planus, Sweet's syndrome, Stevens-Johnson syndrome, staphylococcal scalded skin syndrome, congenital syphilis, skin calcinosis, leprosy, leishmaniasis, phototoxic reactions, bullous amyloidosis)
- Drug-induced milia (steroid atrophy, isotretinoin, cyclosporine, penicillamine)
Pseudomilia: orofaciodigital syndrome type 1, inherited trichodysplasia (Marie-Unna hypotrichosis), anhidrotic ectodermal dysplasia - which resemble milia clinically but not histologically.
Newborn Milia
Observed in 40-50% of cases, newborn milia are small subepidermal papules with a white-yellow color and a diameter of 1-2 mm. The eruptions are mainly localized on the face, including the eyebrows, nose and cheeks. In rare cases, milia may also appear on the hard palate or gums (Epstein's pearls, Bohn's nodules). In most cases, newborn milia spontaneously resolve within a month.
Milia in Children, Adolescents, and Adults
These milia have a persistent and recurrent course. The number of milia can range from a single lesion to hundreds. They occur predominantly on the face, especially in the periorbital region and on the eyelids, and less commonly on the limbs and genitalia. Large solitary lesions may be found on the glans penis, areola of the breasts, scrotum, labia majora, and other areas.
Milia en Plaque
Characterized by multiple grouped milia on the surface of an erythematous and swollen plaque. It is commonly found in the retroauricular region and on the auricle, and less commonly on the eyelids.
Diagnosis is based on the clinical presentation. Histological examination reveals small cystic formations filled with keratin.
- Hydrocystoma
- Syringoma
- Trichoepithelioma
- Eruptive vellus hair cysts
- Molluscum contagiosum
- Sebaceous hyperplasia
Newborn milia regress spontaneously and do not require treatment. In other cases, milia cysts can be removed by carefully incising the formation and extracting the keratinous content. After removal, the condition does not recur, but if new elements appear, similar treatment is performed. There are no preventive methods for milia.