Juvenile-Onset Hypopigmented Mycosis Fungoides Mimicking Vitiligo

Background: Mycosis fungoides (MF) is the most common form of cutaneous T-cell lymphoma and typically affects older adults. It is estimated that less than 5% of MF cases are of juvenile onset. An uncommon hypopigmented variant of MF exists, which has been more commonly observed in dark-skinned individuals and predominantly in juvenile-onset cases. Methods: We describe an 8-year-old otherwise healthy Hispanic male who, by 6 months of age, had developed asymptomatic hypopigmented patches on the lower legs, thighs, and buttocks, which have evolved over the past 7 years. This condition had previously been misdiagnosed as vitiligo. Recent immunohistologic and molecular biology studies are consistent with MF. Results and Conclusions: Given that hypopigmented MF is an uncommon condition, it may not be clinically suspected in the pediatric population. Histopathologic, immunophenotypic, and/or molecular biologic studies are sometimes equivocal, with findings similar to inflammatory dermatoses or autoimmune vitiligo, which may initially lead to a misdiagnosis, as in this patient's case.