Harlequin ichthyosis (HI) is the most severe variant of autosomal recessive congenital ichthyosis (ARCI). It is characterized at birth by the presence of large, thick, plate-like scales over the whole body associated with severe ectropion, eclabium, and flattened ears, that later develops into a severe scaling erythroderma. The disease is autosomal recessive congenital ichthyosis 4B (MONDO_0009443). Also known as: ARCI4B, HI, Harlequin Ichthyosis, autosomal recessive congenital ichthyosis type 4B, harlequin ichthyosis, harlequin type ichthyosis congenita, harlequin type ichthyosis fetalis, hi.