Keratosis lichenoides chronica (KLC), also known as Nekam disease, is a very rare, chronic condition mostly seen in adults. It presents with erythematous, violaceous, or brown-purple, scaly lichenoid papules on the lower trunk and extremities that form linear and/or reticulated plaques, usually symmetrically distributed, and a facial eruption that resembles seborrheic dermatitis or rosacea. It is usually asymptomatic, but pruritus and pain may be accompanying symptoms.

The disease has a slight male predominance, and there does not appear to be any racial / ethnic predilection. 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 and in the summer.

The pathogenesis of KLC has not yet been fully elucidated. Certain clinical differences between adult-onset versus pediatric-onset or congenital KLC have led some authors to speculate that these represent distinct disease entities. While adult-onset KLC is largely considered an acquired condition of unclear etiology, those with juvenile or congenital-onset disease likely represent an autosomal recessive mode of inheritance. Furthermore, cases of germline gain-of-function mutations in the PYD and LRR domains of the NLRP1 gene have been identified in siblings with KLC (familial KLC). Activation of NLRP1 leads to inflammasome assembly, downstream release of proinflammatory mediators such as caspase-1, and subsequent activation of IL-1β and IL-18.

In adults, previous reports have also identified coexistence of KLC with erythroderma, sarcoidosis, hematologic malignancies, and tuberculosis; however, these associations have not been established.