Evaluation of clinical features and follow-up data of childhood mycosis fungoides patients

Objective: The symptoms of mycosis fungoides (MF) begin in a minority of patients in childhood. While some cases are diagnosed in this period, the diagnosis may be delayed into adulthood. In recent years, with expanding of the literature on pediatric MF it has been increasingly suggested that the disease may show some differences in terms of clinical features and have a better prognosis in this period. However, controlled studies are limited in this area. Our study aimed to determine the effect of childhood onset of the disease on the emergence of clinical types, disease stage and course of MF in a large series. Materials and Methods: Consecutive patients who were initially diagnosed with MF or have a follow-up visit with a previous diagnosis between January 2007 and September 2021 in the Department of Dermatology and Venereology of Istanbul University, Istanbul Faculty of Medicine. The patients were divided into three groups according to their age at the onset of the lesions and at the time of the diagnosis. The first two groups consisted of patients diagnosed with MF in the pediatric age (18 years and earlier) and patients with a history of skin lesions of MF in the pediatric age but diagnosed in adulthood (aged 19 and above). The data of the third group consisting of adult-onset patients were considered as the control group. Demographic information of all patients, time to diagnosis, clinical types of MF, and disease stage at the time of diagnosis were recorded. Results regarding demographic information and the frequency of each clinical type were compared with each other in all groups. The cases with at least 3 months of follow-up in the first two groups were evaluated in terms of general stage progression (any progression in the stage after diagnosis) and compared with each other. In addition, the ratio of patients diagnosed in the early and late stages, the rates of progression to the advanced stage (stage IIB and above) during follow-up period, and throughout the entire disease duration were compared between all groups. Results: While 52 (8%) of 651 patients included in our study were diagnosed in the pediatric period, 30 cases (4.6%) were diagnosed with MF in adulthood, but the initial symptoms of the disease had appeared in childhood. In the pediatric group, MF frequently (48.1%) showed coexistence of more than one clinical variant. The classical type of the disease was the most common clinical presentation in all three patient groups. The hypopigmented variant was the second most common (55.8%) clinical type in the pediatric MF group which was detected at significantly higher rates compared to the other two groups. Folliculotropic (17.3%), purpuric (7.7%), and unilesional (7.7%) types were the other clinical types that were more common in this age group compared to the other two groups. On the other hand, in the pediatric-onset adult MF group poikilodermic type (20%) was found at higher rates compared to the other two groups. While all pediatric MF patients were diagnosed at an early stage, 1 patient in the pediatric-onset adult MF group and 7.1% of the patients in the adult-onset MF group were diagnosed with advanced-stage disease. In the pediatric MF group, 32.7% of the patients were diagnosed at stage IB, in contrary in the pediatric-onset adult MF group this rate was 60%. Totally 71 cases from the three groups reached the advanced stage. While none of the cases diagnosed in the pediatric period had advanced stage, the disease progressed to the advanced stage in 2 cases of the pediatric-onset adult MF group. The other 69 patients (%97.2) with progression to the advanced stage belonged to the adult-onset MF group. The rate of patients progressed to the advanced stage was found to be higher in the adult-onset MF group (12.1%) compared to the total number of both pediatric-onset MF groups (2.4%), having a statistically significant difference (p=0.014). Conclusion: In our series, the frequency of pediatric MF was found to be 8%, and the frequency of all childhood-onset MF cases was 12.6%, which could be considered as high. Pediatric MF patients showed some clinical differences from other groups that they often presented with non-classical variants and the co-existence of more than one variant. Furthermore, the hypopigmented, folliculotropic, purpuric, and unilesional MF were common clinical types observed in this period. In contrary, in the pediatric-onset adult MF group, the rate of poikilodermic MF was found to be high, possibly related to the longer disease duration. The fact that pediatric-onset adult group was diagnosed with stage IB disease at a higher rate than the pediatric MF group was evaluated as the long disease duration without treatment caused by delay in diagnosis lead the lesions to become widespread. The establishment of the diagnosis at an early stage in all pediatric MF cases and the absence of progression to the advanced stage in any of these cases, including many patients with folliculotropic type, indicated the benign course of the disease in this age group. The fact that almost all of the patients with advanced stage disease in our series had onset of the lesions in the adulthood also supported this view. Key words: mycosis fungoides, clinical variant, prognosis, pediatric mycosis fungoides, childhood-onset mycosis fungoides