Superficial epidermolytic ichthyosis

Superficial epidermolytic ichthyosis (SEI), also known as ichthyosis bullosa of Siemens (IBS), is a rare genetic skin disorder characterized by superficial blistering and hyperkeratosis (thickening of the outer layer of the skin). It is caused by mutations in the KRT2 gene (keratin 2), which encodes a protein expressed in the upper layers of the epidermis (suprabasal keratinocytes of the granular layer). Because the defective keratin is expressed more superficially in the skin compared to classic epidermolytic ichthyosis, the blistering in SEI tends to be milder and more superficial, with characteristic "mauserung" — a distinctive shedding or molting phenomenon where sheets of superficial skin peel off, particularly over the limbs. Clinical features typically present at birth or in early infancy with episodes of skin fragility, superficial blistering, and peeling. Over time, the blistering tendency may decrease while mild to moderate dark (hyperkeratotic) scaling develops, predominantly affecting the limbs, particularly the shins and flexural areas. The palms and soles are generally spared. The condition is generally milder than classic epidermolytic ichthyosis (caused by KRT1 or KRT10 mutations), and widespread erythroderma is typically absent. Histologically, the skin shows epidermolytic hyperkeratosis confined to the granular and upper spinous layers. There is no cure for superficial epidermolytic ichthyosis. Treatment is symptomatic and supportive, focusing on skin care with regular use of emollients and keratolytic agents (such as urea-based or lactic acid-based creams) to reduce scaling and improve skin texture. Avoidance of excessive heat and friction can help minimize blistering episodes. Retinoids may be considered in more severe cases but must be used cautiously due to potential side effects. Genetic counseling is recommended for affected individuals and their families.

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