Comparison of Pediatric- and Adult-Onset Mycosis Fungoides Patients in Terms of Clinical Features and Prognosis in a Large Series

Studies comparing the clinical and prognostic differences between pediatric- and adult-onset mycosis fungoides (MF) are limited. To determine the impact of childhood-onset MF on clinical features and disease course in a large series. Consecutive MF patients seen in a single centre between 2007 and 2021 were categorized into 3 groups: (i) MF patients diagnosed in the pediatric ages (≤18 years) (pediatric group), (ii) MF patients with disease onset in the pediatric period and diagnosis in adulthood (lately diagnosed pediatric-onset group), and (iii) MF patients with disease onset in the adulthood period (>18 years) (adult-onset group). Demographics, clinical features, stage at diagnosis, and progression to advanced stages during follow-up were recorded and compared. Among 651 MF patients, 52 (8%) belonged to the pediatric group and 30 (4.6%) to the lately diagnosed pediatric-onset group. Pediatric MF presented with a combination of clinical variants in 48.1% of cases. While classical MF was the most common presentation in the 3 groups, hypopigmented (55.8%) and folliculotropic (17.3%) variants were more prevalent in the pediatric group compared to the others. Progression to the advanced stages was higher in the adult-onset MF group (12.1%) compared to the pediatric and lately diagnosed pediatric-onset MF groups (2.4%) ( .014). This study highlights a relatively high prevalence of pediatric MF (8%) and lately diagnosed pediatric-onset MF (4.6%), often presenting with multiple and non-classical clinical variants. The higher rate of progression to advanced stages in the adult-onset group supports the relatively benign nature of MF in the pediatric-onset group.