Focal acral hyperkeratosis is a disorder characterized by hyperkeratotic papules along the border of the hands and feet. Focal acral hyperkeratosis and several marginal punctate keratodermas closely resemble acrokeratoelastoidosis of Costa. The question if there is a difference between acrokeratoelastoidosis of Costa and focal acral hyperkeratosis or if they are variants of the same entity are discussed. We report a case showing focal acral hyperkeratosis, review the clinical and histological features of related conditions and present a modified concept of marginal papular acrokeratodermas.

Necrobiotic xanthogranuloma is a non-X histiocytosis with unknown pathogenesis. It is associated with paraproteinaemia, and in rare cases with multiple myeloma. A decreased level of C1 inhibitor has been found in several cases without clinical manifestations of Quincke oedema. We report on a patient with necrobiotic xanthogranuloma and myeloma, in whom we found a decreased level of C1 inhibitor and recurrent episodes of manifest Quincke oedema. The indirect detection of auto-antibodies against the paraprotein with development of immune complexes is regarded as an explanation for the consumption of the C1 inactivator and the manifestation of Quincke oedema. The possibility of a causal relationship between paraproteinaemia and necrotic xanthogranuloma is discussed.

In the literature, a number of observers reported that acrokeratosis verruciformis (Hopf) often evolves in cases of keratosis follicularis. The relationship of these verruciform manifestations to keratosis follicularis is discussed. In this paper, we present three patients with Darier's disease, who have verruciform papules on the dorsal surfaces of the hands and feet. Histopathologically, the papules showed the distinctive structures of Darier's disease. Therefore, these lesions are regarded as an abortive form of keratosis follicularis. It is necessary to examine carefully the punch biopsies histomorphologically. We also recommend having a closer look at the development of other typical Darier's skin lesions in the follow-up of patients.

Sinus histiocytosis is as a rule a benign disease of lymph nodes, infiltrated by large histiocytes. These cells show typical cytophagocytosis, particularly lymphophagocytosis. Other organs may be also involved by this disease, often including the skin. Exclusive cutaneous sinus histiocytosis without infiltration of lymph nodes seems to be very rare. To exclude other non-X histiocytoses or histiocytosis-X, it is advisable to use immunohistochemistry. We report on a patient with sinus histiocytosis and discuss the problems of differential diagnosis.

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