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Author: Vanessa Ngan, Staff Writer, 2006. Updated by A/Prof Amanda Oakley, March 2016.
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. They are one of the causes of atypical solar lentigo.
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.
Lichenoid keratosis is an inflammatory reaction arising in a regressing existing solar lentigo or seborrhoeic keratosis. It is not known what causes the reaction, but triggers include minor trauma such as friction, drugs, dermatitis, and sun exposure.
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.
The clinical features of lichenoid keratosis vary depending on the inflammatory stage of the lesion.
|Classic, bullous or atypical subtype|
|Early or interface subtype|
|Late regressed or atrophic subtype|
Other features of lichenoid keratosis are:
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.
To date there have been no reports of lichenoid keratosis turning into malignant skin tumours.
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