Congenital ichthyosis constitutes a group of genetic conditions that are not part of a certain syndrome and generally manifests with excessive keratinization of the skin. To this day, five types of congenital, inherited ichthyosis have been described, including X-linked ichthyosis, epidermolytic hyperkeratosis, ichthyosis vulgaris, congenital ichthyosiform erythroderma, and lamellar ichthyosis.
The common characteristic among all congenital ichthyosis types is the abnormal cornification and keratinization of the skin, resulting in dry scales that cover various body parts. Skin inflammation and systemic symptoms can accompany the dermatologic alterations, as can pruritus, anhidrosis, ectropion, and an irregularly dense stratum corneum . Frequently, manifestations are clearly noted at birth. More specifically:
The various types of congenital ichthyosis are usually diagnosed at birth, based on the characteristic appearance of the newborn. In dubious cases, skin biopsy and histological analysis should be employed to ascertain a diagnosis. Steroid sulfatase activity (STS activity), cholesterol sulfate concentration, and genetic testing may be required to diagnose X-linked ichthyosis; lamellar ichthyosis can also be diagnosed via genetic testing. Single-gene testing may be chosen on some occasions .
The differential diagnosis should comprise Refsum disease, neutral lipid storage disease, Sjögren-Larsson syndrome, and Netherton syndrome. A complete workup also requires blood laboratory studies such as serum angiotensin-converting enzyme, lysozyme, complete blood count (CBC), thyroid-stimulating hormone (TSH), triiodothyronine (T3), thyroxine (T4), as well as a chest radiography. Sometimes, congenital ichthyosis can also be detected prenatally via ultrasonography: a persistently open mouth, thick amniotic fluid, and persistently flexed extremities do suggest the possibility of ichthyosis. Diminished serum unconjugated estriol detected in the mother's blood during the period of pregnancy raises suspicion for X-linked ichthyosis.