Pleomorphic ichthyosis: proposed name for a heterogeneous group of congenital ichthyoses with phenotypic shifting and mild residual scaling.

Congenital ichthyosis is often associated with typical neonatal phenotypes, "Collodion baby" and "Harlequin foetus", later transforming into severe lamellar or erythrodermic ichthyosis. However, in a minority of cases the skin condition will improve spontaneously after birth, although slight scaling, xerosis, hypohidrosis and keratoderma usually persist. Some of these patients will eventually be diagnosed as suffering from self-improving collodion ichthyosis, ichthyosis prematurity syndrome, or other, even rarer, forms of ichthyosis also characterized by a phenotypic shift in early childhood. This paper summarizes newly described aetiologies for some of these diseases and discusses difficulties encountered when trying to distinguish them clinically from other types of autosomal recessive congenital ichthyosis. To remind health providers about this heterogeneous group of partially transient disorders of cornification, a new umbrella term, "pleomorphic ichthyosis", is proposed.