Adult-Onset Hypopigmented Mycosis Fungoides: A Systematic Review of Clinicopathologic, Immunophenotypic, and Therapeutic Characteristics

<b>Background/Objectives</b>: Hypopigmented mycosis fungoides (hMF) is a rare variant of mycosis fungoides (MF) often seen in younger patients and individuals with darker skin phototypes. The lesions develop as hypopigmented patches or plaques, and they are usually asymptomatic and respond well to topical treatment or phototherapy. <b>Methods</b>: We provide a systematic review on hMF with onset at or beyond 30 years of age, based on SCOPUS, PubMed, and Embase databases. A total of 13 original articles, totaling 34 patients, were included in this review. Evidence was limited to case reports and small series; PROSPERO registration is CRD420251181894. <b>Results</b>: The majority of cases did not progress beyond stage IB and commonly used treatment methods, including topical corticosteroids and phototherapy. In three patients, a progression of the disease occurred, and in two of them it was fetal. Among patients receiving phototherapy, PUVA therapy achieved complete remission more often than UVB (13 out of 17 cases vs. 8 out of 16 cases). Although recurrences occurred with both treatments, they were less frequent, and relapses took longer to develop in the PUVA group. <b>Conclusions</b>: In this cohort, PUVA appeared to be associated with higher complete response rates and longer remission duration than UVB. However, this advantage of PUVA is derived from low-level evidence and should be confirmed in prospective comparative studies.