Autosomal recessive congenital ichthyoses (ARCI) form a heterogeneous group of disorders characterized by generalized scaling and variable degree of redness of the skin. ARCI manifests at birth or infancy, generally without primary involvement of other organ systems (non-syndromic). The skin features of ARCI may overlap considerably with various types of syndromic ichthyoses (see our website www.genedx.com for information on other types of ichthyoses). The 3 major types of non-syndromic ichthyoses include Harlequin ichthyosis (HI), lamellar ichthyosis (LI) and congenital ichthyosiform erythroderma (CIE).
Most neonates with ARCI present as collodion babies with a taut, translucent or opaque membrane that encases the entire body and lasts for days to two weeks. In severe cases, ectropion, eclabium, and scarring alopecia of the scalp and eyebrows may be present. After shedding the collodion membrane, the presentation and severity of ARCI between individuals can vary significantly. At one end of the spectrum is severe ‘classic’ lamellar ichthyosis (LI), which is characterized by large, dark brown, plate-like scale without underlying erythroderma. At the other end is severe ‘classic’ CIE, with fine, whitish scale and intense redness (erythroderma) of the skin. The clinical features of CIE can be milder than in LI and demonstrate a greater variability in the intensity of redness, scale, and involvement of palms and soles. However, CIE may cause substantial metabolic stress in young children and growth delay. There are also cases of (almost) complete resolution of the skin disorder, so-called ‘self-healing collodion ichthyosis’. Distinguishing between these disorders on clinical grounds can be useful for clarifying prognosis and management and, to some extent, to choose which genes to analyze. A skin biopsy is not necessary to establish the diagnosis of ARCI, and is usually not helpful in differentiating among the different clinical disorders along the spectrum. However, a skin biopsy is useful to differentiate ARCI from the bullous forms of ichthyosis (epidermolytic ichthyosis, also known as epidermolytic hyperkeratosis).