Keratosis lichenoides chronica
The disease affects both sexes about equally. A majority of the patients in the literature are of Northern European descent, although patients of other ethnicities have also been reported. The pathogenesis of KLC has not yet been fully elucidated; however, a gain-of-function mutation in the NLRP1 gene has been identified in a family with KLC. Activation of NLRP1 leads to downstream release of proinflammatory mediators such as caspase-1 and subsequent activation of IL-1β and IL-18.
The mean time to diagnosis of KLC is 9 years given its rarity and similarities to other keratotic skin diseases. While it is a progressive condition, improvement has been reported with aging or in the summer.
L82.1 – Other seborrheic keratosis
373601005 – Keratosis lichenoides chronica
Differential Diagnosis & Pitfalls
- Lichen planus
- Lichenoid drug eruption
- Lichenoid graft-versus-host disease
- Lichen planopilaris
- Inflammatory linear verrucous epidermal nevus (ILVEN)
- Mycosis fungoides – More lesions observed on the thighs and buttocks. Reticulate pattern is formed by pigmentation. In KLC, papules themselves form the reticular pattern.
- Seborrheic dermatitis – KLC spares the nasolabial folds in most cases.
- Malar rash of systemic lupus erythematosus
- Discoid lupus erythematosus
- Subacute cutaneous lupus erythematosus
- Erythromelanosis follicularis faciei et colli