Causes of ichthyosis fall into two main types: inherited (genetic) and acquired. Both lead to similar symptoms, such as dry and scaly skin, but the root causes are different. Knowing the causes of ichthyosis is vital for early diagnosis, treatment, and family planning. It also helps prevent complications and guides patient education.
Inherited Causes of Ichthyosis
Most cases of ichthyosis are inherited. Genetic mutations affect the skin’s outer barrier, called the stratum corneum. This barrier usually protects against water loss, toxins, and germs. When it fails, the skin sheds too slowly or produces too much keratin. This leads to scaling and dryness.
Inherited forms usually appear at birth or within the first year of life, though severity varies. One common type is ichthyosis vulgaris, caused by changes in the FLG gene. This gene helps build the skin barrier. A mutation reduces hydration, making the skin dry and scaly. Even one faulty copy of the gene can cause symptoms, but two copies make it worse.
Another type, X-linked ichthyosis, affects mostly males. It results from a lack of the enzyme steroid sulfatase. This causes cholesterol sulfate to build up in the skin, which damages its structure. It often starts at birth with dark, plate-like scales on the neck, trunk, and limbs.
Severe inherited types include lamellar ichthyosis and congenital ichthyosiform erythroderma. These belong to a group called ARCI (autosomal recessive congenital ichthyoses). They involve mutations in genes such as TGM1, ALOX12B, and ABCA12. Babies with these forms may be born in a shiny “collodion membrane” that peels after birth. These cases need special neonatal care and lifelong treatment.
Acquired Causes of Ichthyosis
Unlike genetic forms, acquired ichthyosis appears later in life. It is often a sign of another illness. Common causes include hypothyroidism, chronic kidney disease, HIV, and Hodgkin lymphoma. Some medicines, like niacin, hydroxyurea, and statins, can also trigger it.
In acquired ichthyosis, the skin usually looks like ichthyosis vulgaris. It often appears first on the legs and then spreads. The exact mechanism is unclear, but experts believe immune problems, lipid imbalance, and slow skin turnover play roles.
Syndromic Causes of Ichthyosis
Some rare conditions include ichthyosis as part of a larger syndrome. Examples are Netherton syndrome (immune and hair issues), Sjögren-Larsson syndrome (neurological problems), and Refsum disease (vision and hearing loss). These cases require care from multiple specialists.
Role of Environment
Weather and habits do not cause ichthyosis but can make it worse. Cold, dry climates, harsh soaps, and frequent hot baths without moisturising often trigger flare-ups. People with mild genetic variants may notice symptoms more in winter.
Genetic Counselling and Testing
Families with inherited ichthyosis should consider genetic counselling. Identifying the mutation helps confirm the diagnosis and assess risks for future children. In severe cases, prenatal testing may be an option. This is especially useful in populations where related parents increase the risk of recessive forms.
Differentiating From Other Conditions
Not all dry, scaly skin is ichthyosis. Conditions like eczema, psoriasis, or simple xerosis can look similar. Knowing the causes of ichthyosis helps doctors rule out these disorders and choose the right treatment.
Summary
The causes of ichthyosis range from genetic mutations to other health conditions and medications. Understanding whether it is inherited or acquired is key to treatment and prevention. Research into the genetic basis of ichthyosis offers hope for new, targeted therapies in the future.
