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Indian Journal of Dermatology, Venereology, Leprology, Vol. 71, No. 1, January-February, 2005, pp. 45-46 Letter To Editor Generalized hypopigmentation due to imatinib: A fairness boon? Sharma Atul, Vora Amish, Bhutani Manisha Department of Medical Oncology, Institute Rotary Cancer Hospital, All India Institute of Medical sciences, New Delhi Code Number: dv05012 Sir, Imatinib (STI571, Glivec©) is a new selective tyrosine kinase inhibitor that is very useful in the treatment of chronic myelogenous leukemia (CML) and gastrointestinal stromal tumors (GIST). More side effects are being reported with its increasing use. We report generalized hypopigmentation with the use of this drug. The majority of CML and GIST patients on imatinib mesylate experience some undesirable side effects that involve many organ systems in the body, including the skin. The most common dermatological side effects are periorbital edema and dermatitis. Facial edema, pruritus, erythema, dry skin, alopecia, night sweats and photosensitivity reaction are infrequently reported.[1] Over 120 patients of CML or GIST are being treated with imatinib at our institute since 2001. For the last one year, during routine outdoor visits, many patients have been reporting that their skin was becoming fairer while on imatinib. We interviewed 26 patients regarding this side effect; 22 of the patients and their relatives confirmed this experience at varying durations of treatment (median 2 months; range 2 to 8 months). Three patients in whom the drug had to be discontinued because of different reasons reported that their skin complexion had reverted to the original one. Skin biopsies were performed on seven of these ′fair′ patients. On H and E staining, even though melanin pigment was seen in all of these biopsy specimens, low melanin content was observed in two of them. In the absence of a pretreatment biopsy, quantification of the melanin pigmentation was not possible. Currently, we are doing electron microscopy and tyramine based tyrosinase assay on the skin biopsies performed pre- and post-imatinib treatment for quantification of the melanin deposition in melanosomes. The exact mechanism for this generalized hypopigmentation with imatinib is not known. Apart from inhibiting a tyrosine kinase, the BCR-ABL oncoprotein, imatinib also inhibits platelet-derived growth factor receptors (PDGFRs) and c-KIT receptor tyrosine kinases.[2] The latter two kinases have important roles in normal pigmentation.[3] Certain hypopigmentary disorders like piebaldism and vitiligo are associated with mutations in the c-KIT gene causing alteration in the respective tyrosine kinases.[4] Tsao et al recently reported a similar finding.[5] However, we found hypopigmentation to be much more common than they did, possibly because it is more apparent in Blacks or Indians because of their otherwise dark skin complexion. Based on our observation, we hypothesize that inhibition of melanocyte c-KIT receptor tyrosine kinase by imatinib leads to generalized hypopigmentation. The long-term implications of this observation need to be studied. Meanwhile, it will be interesting to see whether topical use of imatinib is possible in the future. REFERENCES
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