Ultrastructural features resembling those of harlequin ichthyosis in patients with severe congenital ichthyosiform erythroderma

Congenital ichthyoses are a group of heterogeneous disorders of cornificati on. Autosomal recessive congenital ichthyosis (ARCI) can be clinically subd ivided into congenital ichthyosiform erythroderma and lamellar ichthyosis. Ultrastructurally, ARCI is classified into four groups: ichthyosis congenit a (IC) types I-IV The genetic background of the ARCI disorders is heterogen eous, but only one disease gene, transglutaminase 1, has been detected so f ar. We describe six patients with severe congenital ichthyosis from six dif ferent Scandinavian families. They could not be classified ultrastructurall y into the four IC groups because of atypical findings of electron microsco py. These included abnormal lamellar bodies, alterations in keratohyalin, r emnant organelles and lipid inclusions in the upper epidermal cells, which resembled the ultrastructural findings of harlequin ichthyosis (HI), althou gh the HI phenotype was not present at birth. Some clinical features, such as thick scales, erythroderma, alopecia and ectropion were common to all pa tients. Ichthyosis was usually accentuated in the scalp and four patients h ad clumped fingers and toes. None of the patients carried the transglutamin ase 1 mutation. We conclude that ultrastructural findings resembling those detected in previous HI cases (type 1 and 2) can also be found in patients who do not have classic clinical features of that rare ichthyosis. This may be due to lack of specificity of ultrastructural markers for HI or to its clinical heterogeneity.