Hereditary palmoplantar keratosis of the Gamborg Nielsen type. Clinical and ultrastructural characteristics of a new type of autosomal recessive palmoplantar keratosis.

A new kind of diffuse palmoplantar keratoderma with autosomal recessive inheritance and without associated symptoms was described in Norrbotten, Sweden by Gamborg Nielsen in 1985. Clinically, it ranges between the less severe dominant Unna-Thost type and the more severe recessive Meleda type, as it is milder than the latter. Skin biopsies of five patients from three different families with this new palmoplantar keratoderma, as well as five obligatory heterozygotes from one family, were investigated ultrastructurally in order to characterize this new entity and to differentiate it from the Meleda type. Several features are common to both autosomal recessive palmoplantar keratoses. They show a broadened granular layer, a transit region consisting of cells with a marginal envelope, and considerable hyperkeratosis. Morphologically, this transformation delay is less pronounced in the Gamborg Nielsen type than in the classical Meleda type. As is typical for ridged skin, both types of palmoplantar keratoses possess composite keratohyaline granules. In contrast to the normal appearance of keratohyaline granules in the Meleda type, the Gamborg Nielsen type also shows qualitative deviations of keratohyaline granules with different degrees of spongiosity and electron density and sometimes with a granular border. It seems that abnormal keratohyaline proteins are synthesized that behave differently. The sudden transformation of a granular into a horny cell is physiologically regulated by different enzymes. A delay in this process may be caused by a mutation that reduces or alters the enzymes concerned. We assume the palmoplantar keratoderma of the Gamborg Nielsen type to be a variant of the heterogeneous group of the Meleda type of palmoplantar keratoderma with autosomal recessive inheritance.