An erythrodermic skin disease occurring in a patient with an already existing erythroderma of different cause is a rare phenomenon. A 13 year old girl with congenital lamellar ichthyosis suffered from both erythroderma and generalized scaling. Probably at the age of 11, a clinically not recognized psoriatic erythroderma appeared associated with a pustular palmoplantar psoriasis of the Barber-Königsbeck type as well as a psoriatic osteoarthropathy. The identification off such overlapping disorders is of great importance for proper therapy.