Case 1: Rete ridge hyperplasia and hyperparakeratosis creates a villous or papillary look.
Acantholysis (loss of epidermal adhesions) and dyskeratosis (abnormal premature keratinization) are the two main features. Acantholysis leads to the suprabasilar split.
Darier disease (a.k.a keratosis follicularis) is an inherited, autosomal-dominant blistering skin disease. Mutation in the ATP2A2 gene which encodes a calcium pump is responsible for the manifestation of the disease, although the exact mechanism is not known. One postulation is that alterations in calcium regulation affect the synthesis, folding, or trafficking of desmosomal proteins.
Histologically, this condition is characterized by acantholysis and dyskeratosis. Two types of dyskeratotic cells -- "corps ronds" and "corps grains" -- may be seen. The histology is actually a warty dyskeratoma, although the latter is usually an isolated sporadic lesion.
Corp ronds are large acantholytic keratinocytes with a dark nucleus and a perinuclear halo; these are seen in the spinous layer. Corp grains are smaller keratinocytes with pyknotic nuclei and shrunken pink cytoplasm; these are seen in the granular layer and the stratum corneum (Busam).
Patients present with greasy hyperkeratotic papules in seborrheic regions (e.g. postauricular scalp, chest, back). The palms and soles may be involved as well. Often, there may be nail changes and mucous membrane lesions (e.g whitish papules on oral mucosa). Onset is variable but most common during adolescence. Lesions are frequently itchy. Exacerbating factors include heat, sweat, humidity, sunlight, steroid and mechanical trauma (Kwok).
Moisturizers with urea or lactic acid can reduce scaling and hyperkeratosis. Topical steroid and retinoids are sometimes useful. Oral retinoids may also be employed.
A benign condition although the odor of the lesions and cosmetic issues (when widespread) may cause significant emotional distress.
Busam KJ. Dermatopathology: Foundations in Diagnostic Pathology 1st Ed. Philadelphia, PA: Elsevier; 2010: 227-8.
Kwok PY. Keratosis Follicularis (Darier Disease): eMedicine. Last updated May 14 2010. Available at: emedicine.medscape.com/article/1107340