Acrokeratosis verruciformis is a rare genodermatosis with an autosomal dominant mode of inheritance. Acrokeratosis verruciformis is a disorder of keratinization characterized by multiple flat-topped, skin-colored keratotic lesions resembling plane warts typically observed on the dorsum of the hands and feet. Hopf first suggested the name acrokeratosis verruciformis in 1931.  In 1947, Niedleman first published the largest series describing an Italian American family in which acrokeratosis verruciformis of Hopf occurred in 14 members. In the follow-up study in 1962, Niedleman and McKusick further described 24 cases in 4 generations of the same family.  The number and distribution of cases in the latter report suggested an autosomal dominant mode of transmission. 
Lesions identical to those of acrokeratosis verruciformis are also observed in many patients with acral Darier disease (also termed keratosis follicularis) or even in relatives of individuals with Darier disease. Considerable controversy surrounds the nature and relationship of acrokeratosis and Darier disease and whether they are manifestations of one genetic abnormality. Some authors suggest that acrokeratosis verruciformis of Hopf and Darier disease are distinct entities, while others maintain that they are variable expressions of the same disease, with the former being a mild expression or a forme fruste of the latter. [4, 5] Recent genetic studies review how these may be distinct entities that are allelic variants. 
Darier disease (keratosis follicularis) is the most important disorder to be distinguished from acrokeratosis. Darier disease, acrokeratosis verruciformis, epidermodysplasia verruciformis, plane warts, and seborrheic keratoses can be differentiated on the basis of histologic examination findings from biopsy samples from individual lesions. The hard nevus of Unna can be differentiated clinically on the basis of its late onset. [5, 7, 8]
Acrokeratosis verruciformis has an autosomal dominant mode of inheritance. The close clinical and histological similarity of acrokeratosis verruciformis of Hopf to the acral lesions of keratosis follicularis (Darier disease) has been noted by Hopf and Darier themselves. The similarities led later observers to postulate a relationship between the 2 diseases. The exact relationship between acrokeratosis verruciformis and Darier disease is still controversial. A classic case of Darier disease poses no diagnostic problem. However, deciding whether a mild case of Darier disease represents, in fact, acrokeratosis verruciformis, remains difficult.
Although clinically similar, acrokeratosis verruciformis is thought to remain nondyskeratotic and nonacantholytic throughout life, whereas acral lesions of Darier disease show, upon careful histologic examination, various gradations of acantholytic dyskeratosis, especially in older lesions. Basically, the keratinization process in acrokeratosis verruciformis is exaggerated but normal, whereas in Darier disease, it is accentuated, altered, and faulty. 
A mutation in ATP2A2, a gene situated on band 12q23-q24 encoding for sarco(endo)plasmic reticulum Ca2+ ATPase2 (SERCA2), is the cause of Darier disease.  A total of 162 mutations in this gene have been reported to date that are thought to be associated with Darier disease.  SERCA2 is a calcium pump of sarcoplasmic/endoplasmic reticulum that plays a role in intracellular signaling. Although the relationship between these conditions is controversial, two distinct mutations in ATP2A2 have been found in acrokeratosis verruciformis that are not seen in Darier disease. [11, 12, 10] This finding suggests that the two diseases are allelic disorders with phenotypic expression of different severities. A more recent study provides evidence for genetic heterogeneity of acrokeratosis verruciformis and demonstrates that mutations in genes other than ATP2A2 are responsible for acrokeratosis verruciformis in some patients. [13, 14]
Acrokeratosis verruciformis of Hopf is a rare genodermatosis.
Acrokeratosis verruciformis has been described in individuals of many races.
No sex predilection has been reported for acrokeratosis verruciformis of Hopf.
Acrokeratosis verruciformis is usually present at birth or manifests in early childhood. Onset may be delayed until the fifth decade of life.
Lesions tend to persist throughout life and become more prominent following prolonged sun exposure.