Netherton syndrome is a disorder that affects the skin, hair, and immune system. Newborns with Netherton syndrome have skin that is red and scaly (ichthyosiform erythroderma), and the skin may leak fluid. Some affected infants are born with a tight, clear sheath covering their skin called a collodion membrane. This membrane is usually shed during the first few weeks of life. Because newborns with this disorder are missing the protection provided by normal skin, they are at risk of becoming dehydrated and developing infections in the skin or throughout the body (sepsis), which can be life-threatening. Affected babies may also fail to grow and gain weight at the expected rate (failure to thrive). The health of older children and adults with Netherton syndrome usually improves, although they often remain underweight and of short stature.

After infancy, the severity of the skin abnormalities varies among people with Netherton syndrome and can fluctuate over time. The skin may continue to be red and scaly, especially during the first few years of life. Some affected individuals have intermittent redness or experience outbreaks of a distinctive skin abnormality called ichthyosis linearis circumflexa, involving patches of multiple ring-like lesions. The triggers for the outbreaks are not known, but researchers suggest that stress or infections may be involved.

Itchiness is a common problem for affected individuals, and scratching can lead to frequent infections. Dead skin cells are shed at an abnormal rate and often accumulate in the ear canals, which can affect hearing if not removed regularly. The skin is abnormally absorbent of substances such as lotions and ointments, which can result in excessive blood levels of some topical medications. Because the ability of the skin to protect against heat and cold is impaired, affected individuals may have difficulty regulating their body temperature.

People with Netherton syndrome have hair that is fragile and breaks easily. Some strands of hair vary in diameter, with thicker and thinner spots. This feature is known as bamboo hair, trichorrhexis nodosa, or trichorrhexis invaginata. In addition to the hair on the scalp, the eyelashes and eyebrows may be affected. The hair abnormality in Netherton syndrome may not be noticed in infancy because babies often have sparse hair.

Most people with Netherton syndrome have immune system-related problems such as food allergies, hay fever, asthma, or an inflammatory skin disorder called eczema.

Netherton syndrome is caused by mutations in the SPINK5 gene. This gene provides instructions for making a protein called LEKT1. LEKT1 is a type of serine peptidase inhibitor. Serine peptidase inhibitors control the activity of enzymes called serine peptidases, which break down other proteins. LEKT1 is found in the skin and in the thymus, which is a gland located behind the breastbone that plays an important role in the immune system by producing white blood cells called lymphocytes. LEKT1 controls the activity of certain serine peptidases in the outer layer of skin (the epidermis), especially the tough outer surface known as the stratum corneum, which provides a sturdy barrier between the body and its environment. Serine peptidase enzymes are involved in normal skin shedding by helping to break the connections between cells of the stratum corneum. LEKT1 is also involved in normal hair growth, the development of lymphocytes in the thymus, and the control of peptidases that trigger immune system function.

Mutations in the SPINK5 gene result in a LEKT1 protein that is unable to control serine peptidase activity. The lack of LEKT1 function allows the serine peptidases to be abnormally active and break down too many proteins in the stratum corneum. As a result, too much skin shedding takes place, and the stratum corneum is too thin and breaks down easily, resulting in the skin abnormalities that occur in Netherton syndrome. Loss of LEKT1 function also results in abnormal hair growth and immune dysfunction that leads to allergies, asthma, and eczema.

Normal Function

The SPINK5 gene provides instructions for making a protein called LEKT1. LEKT1 is a type of serine peptidase inhibitor. Serine peptidase inhibitors control the activity of enzymes called serine peptidases, which break down other proteins. LEKT1 is found in the skin and in the thymus, which is a gland located behind the breastbone that plays an important role in the immune system by producing white blood cells called lymphocytes. LEKT1 controls the activity of certain serine peptidases in the outer layer of skin (the epidermis), especially the tough outer surface known as the stratum corneum, which provides a sturdy barrier between the body and its environment. Serine peptidase enzymes are involved in normal skin shedding by helping to break the connections between cells of the stratum corneum. LEKT1 is also involved in normal hair growth, the development of lymphocytes in the thymus, and the control of peptidases that trigger immune system function.

Health Conditions Related to Genetic Changes

Netherton syndrome

At least 70 SPINK5 gene mutations have been identified in people with Netherton syndrome, a disorder involving skin and hair abnormalities and a high risk of allergies, asthma, and an inflammatory skin condition called eczema. Mutations in the SPINK5 gene result in a LEKT1 protein that is unable to control serine peptidase activity. The lack of LEKT1 function allows the serine peptidases to be abnormally active and break down too many proteins in the stratum corneum. As a result, excessive skin shedding takes place, and the stratum corneum is unusually thin and breaks down easily, resulting in the skin abnormalities that occur in Netherton syndrome. Loss of LEKT1 function also results in abnormal hair growth. The immune dysfunction that leads to allergies, asthma, and eczema in people with Netherton syndrome likely arises from a lack of LEKT1 control of peptidases involved in the triggering of immune system function. Excessive activation of the immune system caused by invasion of microbes in the abnormal skin is also thought to be involved.

Other disorders

Normal variations (polymorphisms) in the SPINK5 gene have been associated with an increased risk of abnormal triggering (hypersensitivity) of the immune system, known as atopy. Atopy leads to disorders such as allergies, eczema, and asthma. SPINK5 gene variations may affect the ability of LEKT1 to control peptidases involved in triggering the immune system, leading to an increased risk of these disorders.

Other Names for This Gene

• DKFZp686K19184
• FLJ21544
• FLJ97536
• FLJ97596
• FLJ99794
• ISK5_HUMAN
• LEKTI
• LETKI
• lympho-epithelial Kazal-type-related inhibitor
• lymphoepithelial Kazal-type-related inhibitor
• NETS
• NS
• serine protease inhibitor Kazal-type 5
• serine protease inhibitor, Kazal type 5
• VAKTI

Genomic Location

• Excessively dry scaly skin (ichthyosis)
• Darkened and thickened skin (acanthosis nigricans)
• Red skin and fine scales on the skin (congenital nonbullous ichthyosiform erythroderma)
• Brittle hair with an abnormal hair shaft (bamboo hair)
• Predisposition to develop allergic reactions (atopic diathesis)
• Eczema
• Asthma
• Trouble absorbing nutrients from food (malabsorption)