Discussion
KLC is considered by some to be a variant of lichen planus while others believe that it has a distinct clinical and histological picture(4). The combination of lichenoid keratotic papules with a characteristic linear/reticular arrangement with an erythematous facial eruption refers to the clinical diagnosis of KLC. The histologic features of KLC are variable and nonspecific; however, the presence of parakeratosis and heavier infiltration than what usually seen in lichen planus may help in differentiation(4).
Although children are occasionally affected, the majority of reported KLC cases are adults. In 2007 Ruiz-Maldonado et al. studied 14 cases of pediatric-onset KLC and compared them with adult-onset KLC (3). They proposed that some features of KLC might characterize pediatric-onset KLC including an early or congenital onset, a positive family history with a probable autosomal recessive inheritance, a greater proportion of male to female, an initial location of lesions on the face with erythematous-purpuric macules, forehead, eyebrow, and eyelash alopecia, the higher frequency of pruritus, and a much lower frequency of mucosal involvement and systemic abnormalities (3). Our patient began to develop skin lesions during the first year of her life making her a pediatric-onset KLC but she presented with features more consistent with those of adult-onset KLC. First, the lesions had appeared on the chest instead of the face. Indeed, her facial rosacea-like lesions were a recent phenomenon. Secondly, extensive oral erosions and prominent nail involvement in our case are other dermatological alterations seen in 50% and 30% of adult-onset patients respectively (3) but occurring infrequently in children. Negative family history and lack of alopecia are also in favor of adult-onset disease.
The other less common features of KLC are summarized in Table 1.
KLC has a chronic course with a gradual progression and most cases have failed to show a favorable response to any treatment with a mean follow-up time of 14 years in adults(3). Several anecdotal reports have shown the efficacy of ultraviolet A- and ultraviolet B-light phototherapies, natural light, photochemotherapy, and oral retinoids (acitretin or isotretinoin) plus phototherapy.(3) In our case, the patient showed a partial response to treatment with acitretin but phototherapy was not feasible due to the COVID-19 outbreak. Based on the current data systemic corticosteroids, antimalarial agents, sulfones, gold, and cyclosporine are proven to be ineffective in the treatment of KLC(4).