Juvenile-onset hypopigmented mycosis fungoides mimicking vitiligo

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.

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.

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.