Imatinib induced lichen planus.

Sir,

A 32-year-old man was referred with multiple hyperpigmented, itchy raised lesions over the scalp, face, neck, shoulders, and limbs of 3 weeks duration. The lesions had started on the limbs, and later involved the face and shoulders. There was no history of blisters occurring over the lesions or involvement of the other parts of trunk. Apparently, 5 months before the onset of the skin lesions he had been started on imatinib mesylate (400 mg/day) for chronic myeloid leukemia with a total leukocyte count of 2,17,600 with abnormal cell 85% at the time of initiation of therapy. Following the initiation of therapy, he had noticed generalized lightening of skin color after 1 month which resolved on its own. He had also been on treatment with tablet paracetemol and multivitamins during the course of therapy. Cutaneous examination revealed multiple well-defined hyperpigmented violaceous plaques over the extensors of the hands, legs [Figure 1], face [Figure 2], and upper shoulders with a similar plaque over the scalp associated with alopecia. Histopathology of a representative lesion revealed hyperkeratotic, hyperplastic squamous epithelium, pigment incontinence, and a band of mononuclear infiltrate in subepithelial tissue eroding the dermoepidermal junction [Figure 3], suggestive of lichen planus. Serological tests for HIV, HbsAg, and HCV were negative. A diagnosis of lichen planus probably induced by imatinib mesylate was done, and he was treated with topical clobetasol propionate and antihistamines. Since the nature of the adverse cutaneous drug reaction was not severe, the drug was not interrupted but the patient was advised to follow up at monthly intervals with a suggestion to the hemato-oncologist about the early dose reduction of imatinib if the clinical and lab parameters permit. The patient had shown complete flattening of the plaques with postinflammatory hyperpigmentation at 3 months of follow-up and was on dose reduction. The patient was taken off topical steroids and continued to be in clinical remission at 6 months follow-up.

Figure 1

Multiple hyperpigmented plaques on bilateral legs

Figure 2

Multiple purplish papules on face

Figure 3

Histopathology showing interface dermatitis

Lichen planus-like or lichenoid eruptions describe a group of cutaneous reactions identical to lichen planus, with localized or generalized eczematous papules and plaques and variable desquamation, but with characteristic differences. Lichenoid drug eruptions typically appear symmetrically on the trunk and extremities (photo-distributed pattern), unlike the flexural distribution of classic lichen planus, do not exhibit Wickham striae and heal with prominent postinflammatory hyperpigmentation. The occurrence of these lichenoid lesions is usually dose dependant.[1]

Imatinib is recommended as first-line therapy in newly diagnosed patients with Philadelphia chromosome-positive chronic myeloid leukemia at a daily dose of 400 mg. A higher dose of 600 mg per day is recommended in accelerated or myeloid blastic phases of the disease, escalated to 800–1000 mg if an adequate hematologic or cytogenetic response is not observed.[2] Lichenoid reactions have generally been reported at dosages of 400 mg/day and have been variably treated with topical steroids, systemic steroids, imatinib interruption, and restarting at a lower dose with periodic escalation. Considering the fact that tolerance occurs with imatinib therapy and severe skin reactions are generally seen at 600–1000 mg/day,[2] we continued the patient on the same dose and the lesions disappeared with topical therapy and dose reduction suggesting a sublesional dose as occurrence of lichenoid reaction with imatinib is a pharmacological effect rather than hypersensitivity.[3] This case underlines the complete resolution of skin lesions with topical therapy and early dose reduction with disease remission, without interruption of therapy.