Pachyonychia congenita with cutaneous amyloidosis and hyperpigmentation--a distinct variant.

Two kindreds manifesting an unusual form of pachyonychia congenita are described. Clinical involvement consists of nail dystrophy, which tends to improve with age, and moderate palmoplantar hyperkeratosis. In addition, all affected members show a characteristic pattern of cutaneous hyperpigmentation, which resembles macular amyloidosis around the neck and waist, but which confers a dappled appearance to the axillae, popliteal fossae, thighs, buttocks, and lower aspect of the abdomen. With advancing age the pigmentation fades. Histologic and ultrastructural examination of the hyperpigmented skin has revealed pigmentary incontinence and deposition of amyloid within the papillary dermis. These features appear to constitute a distinct variant of pachyonychia congenita.