Collodion baby and loricrin keratoderma: a case report and mutation analysis

Hereditary palmoplantar keratodermas (PPK) comprise a clinically and genetically heterogeneous group of genodermatoses, which share the characteristic of impaired epidermal differentiation, resulting in prominent palmoplantar hyperkeratosis. Molecular genetic analyses have helped characterize the underlying genetic defects in an increasing number of hereditary PPKs over the past two decades, and thus a pathophysiological classificaiton seems more reasonable. Today PPK can be classified based on defects in keratins, loricrin, desmosomes, connexins and cathepsins. In this report, we describe a 22-year-old man who had been born a collodion baby, and later developed diffuse PPK with pseudoainhum and generalized ichthyosis. His mother and grandmother had similar characteristics. Direct sequencing of genomic DNA identified a frameshift insertion mutation (730insG) in the loricrin gene. This family had the typical presentation of loricrin keratoderma. It also indicates that collodion baby may be the first presentation in patients with loricrin keratoderma.