ichthyosis

Ichthyosis is a family of genetic skin disorders characterized by generalized dry, scaly skin due to abnormal keratinization. In affected individuals the skin barrier is often impaired, leading to persistent scaling, rough texture, and sometimes itching or fissures. The severity and distribution of symptoms vary widely among different forms, from mild, easily managed conditions to severe, lifelong diseases.

The main forms include ichthyosis vulgaris, X-linked ichthyosis, and autosomal recessive congenital ichthyosis (ARCI). Ichthyosis vulgaris is the most common form and is usually inherited in an autosomal dominant pattern; it commonly involves the extensor surfaces and is linked to reduced filaggrin (FLG) expression. X-linked ichthyosis is caused by steroid sulfatase (STS) deficiency and typically affects males, with scales on the trunk and limbs. ARCI encompasses lamellar ichthyosis and nonbullous congenital ichthyosiform erythroderma (CIE); these forms are usually autosomal recessive and often involve mutations in ABCA12, TGM1, or other genes. Harlequin ichthyosis is a rare, severe neonatal form within the lamellar-spectrum, historically associated with ABCA12 mutations.

Diagnosis relies on clinical assessment and family history; genetic testing can confirm subtype and guide counseling. Differential diagnosis includes other causes of generalized scales and erythroderma.

Management is lifelong and focuses on skin hydration and scale reduction. Regular use of emollients, moisturizers, and keratolytics (such as urea or lactic acid) is typical. Topical retinoids may be used in some cases, while systemic retinoids (acitretin or isotretinoin) are reserved for severe ARCI under specialist supervision due to potential side effects. Monitoring for infections and heat intolerance is important; prognosis varies with form and severity.