Lichenoid keratosis

Author: Vanessa Ngan, Staff Writer, 2006. Updated by A/Prof Amanda Oakley, March 2016.

What is lichenoid keratosis?

Lichenoid keratosis is usually a small, solitary, inflamed macule or thin pigmented plaque. Multiple eruptive lichenoid keratoses in sun-exposed sites are also described. Their colour varies from an initial reddish brown to a greyish purple/brown as the lesion resolves several weeks or months later.

Lichenoid keratosis is also known as benign lichenoid keratosis, solitary lichen planus, lichen planus-like keratosis and involuting lichenoid plaque.

Who gets lichenoid keratosis?

Lichenoid keratosis generally develops in fair-skinned patients aged 30–80 years. It is twice as common in females as than males. It is most commonly seen in Caucasians and rarely affects Asians, African Americans or Hispanics.

What causes lichenoid keratosis?

Lichenoid keratosis is an inflammatory reaction arising in a regressing existing solar lentigo or seborrhoeic keratosis. It is not known what triggers the reaction, but triggers include minor trauma such as friction, drugs, dermatitis, and sun exposure.

How is lichenoid keratosis diagnosed?

Lichenoid keratosis is diagnosed by its clinical and dermoscopic appearance, which reveals uniform clusters of grey dots and, depending on the stage of the lesion, may show signs of an original pre-existing lentigo or seborrhoeic keratosis. In time, signs of the original lesion disappear. Later on the grey dots also disappear, as the lesion resolves to reveal normal skin.

Because clinical examination and dermatoscopy may not be able to differentiate between lichenoid keratosis and other solitary erythematous lesions that could be melanocytic, non-melanocytic benign, malignant or inflammatory, a punch or shave skin biopsy may be necessary.

Histopathology of resembles that of lichen planus or lichenoid drug eruption, with some slight differences. Remnants of the original solar lentigo or seborrhoeic keratosis may be evident.

What are the clinical features of lichenoid keratosis?

The clinical features of lichenoid keratosis vary depending on the inflammatory stage of the lesion.

Classic, bullous or atypical subtype
Clinical features
  • Acute rapidly developing lesion (present for <3 months)
  • Erythematous or pinkish papule or plaque
  • Dermoscopy may show remnants of pigment network, subtle blotches of brown colour, clusters of grey dots plus dotted, irregular linear and other shaped telangiectatic blood vessels
Histopathology
  • Classic variant shows epidermal acanthosis with a band-like lichenoid lymphocytic infiltrate. Presence of epidermal parakeratosis distinguishes these lesions from typical lichen planus.
  • Bullous variant shows intraepidermal or subepidermal bullous cavities with dense lymphocytic infiltrate and increased number of necrotic basilar layer keratinocytes.
  • Atypical variant shows similar histology to classic type with scattered enlarged CD-3, CD-30 (+) lymphocytes with hyperchromatic, irregular nuclei.
Early or interface subtype
Clinical features
  • Subacute lesions present for 3 months to one year
  • Erythematous to dusky-red or hyper-pigmented brown lesion
  • Depending on the age of lesion, dermoscopy may show features of a solar lentigo or flat seborrhoeic keratosis with moth-eaten borders, fingerprinting, milia-like cysts, comedo-like openings, plus small foci of melanophages (grey dots).
Histopathology
  • Single lymphocytes aligned along the dermoepidermal junction without epidermal acanthosis and adjacent lentigo
Late regressed or atrophic subtype
Clinical features
  • Lesions have been present for more than one year
  • May be violaceous (violet-coloured) papules or irregularly distributed lesions with shades of brown or grey
Histopathology
  • Epidermal atrophy with papillary dermal scarring, patchy lymphocytic infiltrates and melanin incontinence

Other features of lichenoid keratosis are:

What is the management of lichenoid keratosis?

Lichenoid keratosis is harmless and resolves spontaneously. If there is any doubt about the diagnosis, dermatoscopic digital images can be taken and used in follow-up a few months later.

Lichenoid keratosis can be removed if desired by liquid nitrogen, electrosurgery or curettage.

Multiple eruptive lichenoid keratoses may be effectively treated with the oral retinoid, acitretin.

To date there have been no reports of lichenoid keratosis turning into malignant skin tumours.

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