Friday 12 October 2012
Acantholytic dyskeratosis is a histological reaction pattern characterized by suprabasilar clefting with acantholytic and dyskeratotic cells at all levels of the epidermis.
It may also be regarded as a special subdivision of the vesiculobullous tissue reaction, but the vesiculation is not usually apparent clinically and the primary abnormality involves the tonofilament–desmosome complex with disordered epidermal maturation.
Like epidermolytic hyperkeratosis, acantholytic dyskeratosis may be found in a number of different clinical settings.
The two histological patterns have even been found in the same biopsy.
Acantholytic dyskeratosis may be:
generalized: Darier’s disease
systematized or linear: zosteriform (segmental) Darier’s disease or linear nevus
transient: Grover’s disease
palmoplantar: a very rare form of keratoderma
solitary: warty dyskeratoma
incidental: focal acantholytic dyskeratosis
solar keratosis related: acantholytic solar keratosis
mucosal: vulval and anal acantholytic dyskeratosis.
Of the various clinical settings listed above, focal acantholytic dyskeratosis, Darier’s disease, Grover’s disease, and warty dyskeratoma will be considered separately. Hailey–Hailey disease (familial benign chronic pemphigus) is also included in this section because of some overlap features with Darier’s disease.
However, in Hailey–Hailey disease the acantholysis is more extensive and dyskeratosis is not a prominent feature. Only brief mention will be made of the other clinical settings because of their rarity or because they belong more appropriately to another section of this volume.
The occurrence of acantholytic dyskeratosis in lesions with a linear or systematized distribution is best regarded as an example of segmental Darier’s disease induced by postzygotic mosaicism, and not as an example of epidermal nevus as previously thought.
It is now well known that autosomal dominant skin disorders may sometimes become manifest in a mosaic form, involving the body in a linear, patchy, or circumscribed arrangement.
The segmental disease usually shows the same degree of severity as that found in the corresponding non-mosaic trait.
Loss of heterozygosity for the same allele causes more severe changes.
Segmental Darier’s disease shows the same mutations in the ATP2A2 gene that occur in generalized Darier’s disease. Unaffected skin does not show this mutation in keeping with mosaicism.
Acantholytic dyskeratosis is an uncommon finding in ‘epidermal nevi’, being present in only 2 of a series of 167 epidermal nevi reported from the Mayo Clinic.
Such lesions would have followed Blaschko’s lines, reflecting as it does genetic mosaicism.
The sole of the foot is a rare site for segmental disease.
Acantholytic dyskeratosis has also been reported as a rare pattern in familial dyskeratotic comedones, a condition with some features in common with nevus comedonicus.
Acantholytic dyskeratosis appears to affect cells within the germinative cellular pool of the epidermis.
The dyskeratosis that occurs within the acantholytic cells is probably a secondary phenomenon as the acantholytic cells are metabolically inert.