Lichen nitidus in a child receiving adalimumab for juvenile idiopathic arthritis

Sir,

The use of biological agents to block specific immune system targets has been associated with onset or worsening of both organ-specific and systemic inflammatory conditions. Lichen planus and other lichenoid reactions have been reported occasionally in patients receiving antitumor necrosis factor-a agents.¹ We report the first case of lichen nitidus in a child receiving adalimumab for juvenile idiopathic arthritis.

A 9-year-old boy, receiving adalimumab for juvenile idiopathic arthritis, presented with mildly pruritic skin lesions for last 1 year. Medical history was significant for oligoarticular juvenile idiopathic arthritis since 2 years age. Previous therapies included methotrexate and etanercept, none being effective. Treatment with adalimumab, started 6 months prior to skin eruption, achieved an excellent control of joint disease.

A detailed physical examination revealed multiple shiny, skin-colored, flat-topped papules measuring up to 2 mm in diameter, predominantly affecting the trunk and the extremities [Figures 1a and b]. Lesional histology demonstrated epidermal thinning and thickened papillary dermis with intense lymphocytic infiltration embraced by rete ridges, consistent with the typical ‘ball-claw’ sign [Figure 2]. Thus, we made a diagnosis of lichen nitidus. We prescribed topical methylprednisolone to obtain partial improvement.

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Figure 1a:

Shiny, skin-colored, papules, affecting the trunk

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Figure 1b:

The extensor aspect of the limb

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Figure 2:

The typical ball-claw sign in biopsy (H and E, ×400)

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A year later, our patient developed an upper-tract respiratory infection, and adalimumab was discontinued, resulting in complete resolution of skin lesions by 4 weeks. After 2 months, adalimumab was restarted and a second episode of lichen nitidus developed with subsequent injections. Two years later, adalimumab was suspended due to stability of joint disease, and lichen nitidus resolved again. A joint relapse warranted re-introduction of adalimumab, leading to a third episode of lichen nitidus. Treatment with topical steroids achieved complete remission of skin lesions.

Lichen nitidus is a relatively uncommon, asymptomatic or mildly pruritic, chronic eruption, characterized by pinpoint, skin-colored or pinkish papules. It is frequently seen in children and young adults with male predilection (4:1). Its pathogenesis remains unclear, but immunological and genetic factors have been proposed. A generalized variant has been reported in children with Down syndrome, Niemann-Pick disease, and other syndromes.²

Although a single case of lichen nitidus has been reported along with juvenile idiopathic arthritis, our case was unique as all three episodes showed temporal association with an anti-tumor necrosis factor-a agent, adalimumab,³ and drug withdrawl resulted in resolution of lesions on each occasion. This finding suggests a strong causal association between adalimumab and lichen nitidus. Lichen planus and other lichenoid reactions have been reported with anti-tumor necrosis factor-a agents.⁴ We hypothesized that adalimumab induced cytokine imbalance to be a triggering factor for lichen nitidus. The blockade of tumor necrosis factor-a results in excess interferon-a activity, which amplifies T-cell response by induction and overexpression of chemokine receptors like CXCR3, subsequently promoting T-cell migration to other tissues, especially skin.⁵

We were unable to find any previous report of lichen nitidus induced by tumor necrosis factor-a blockade with adalimumab. Blockage of specific immune targets may alter the cytokine milieu, resulting in inflammatory lichenoid reactions like lichen nitidus in predisposed individuals. A detailed review of symptoms, medication and comorbidities is mandatory in such patients. Further observations are needed to confirm this association.