Question
What are the clinical features of childhood mycosis fungoides (MF)?
Findings
In this systematic review of 571 children and adolescents with MF, the most common subtype was the hypopigmented form, followed by classic MF. Most patients with MF presented with early-stage disease, and the prognosis of MF seems to be more favorable than in the general population, although a significant delay before the establishment of a correct diagnosis of MF in childhood was associated with a poor prognosis.
Meaning
These findings suggest that although the prognosis of childhood MF is not unfavorable, delayed diagnosis may have an adverse effect.
Importance
Comprehensive data on childhood mycosis fungoides (MF) is scarce.
Objective
To describe clinical features, immunophenotypes, various treatment options, and prognosis of MF in children and adolescents.
Evidence Review
This systematic review searched MEDLINE via PubMed, Embase, Cochrane, and Scopus databases in October 2019. The search terms included mycosis fungoides, infant, children, and adolescent. No filter for the publication period was used, but studies written in a language other than English were excluded. Reference lists of the relevant articles were also searched manually. Case series and case reports were included if data on childhood MF were extractable. The Asan Medical Center database for cases of childhood MF was also searched. Patients were treated from January 1, 1990, to July 31, 2019, and were younger than 20 years at the time of diagnosis. The methodologic quality of the included studies was assessed with items from the Newcastle-Ottawa scale. Data were analyzed from December 9, 2019, to September 4, 2020.
Findings
A total of 571 unique patients were included. The mean (SD) age at diagnosis was 12.2 (4.2) years; at onset, 8.6 (4.2) years. The female-to-male ratio was 1:1.6 (350 male patients [61.3%]). Among 522 patients with data available at diagnosis, stage 1 disease constituted 478 cases (91.6%), followed by stage 2 (39 [7.5%]) and stage 4 (5 [1.0%]). Among the 567 patients with data available, the most common variant of MF was the hypopigmented form (309 [54.5%]), followed by classic MF (187 [33.0%]). The MF lesions were predominantly the CD4+ and CD8+ immunophenotype in 99 (49.5%) and 79 (39.5%) of 200 patients, respectively. Among the treatments, narrowband UV-B was the most frequently used (150 of 426 [35.2%]). Most patients were alive with the disease (185 of 279 [66.3%]); 83 of 279 (29.8%) were in complete remission; and 11 of 279 (3.9%) had died by the last follow-up. A longer time from onset to diagnosis (hazard ratio [HR], 1.24; 95% CI, 1.06-1.45), granulomatous slack skin (HR, 12.25; 95% CI, 1.99-75.26), granulomatous MF (HR, 14.59; 95% CI, 1.31-162.00), a history of organ transplant (HR, 10.15; 95% CI, 0.98-105.37), and stage 2 disease at the time of diagnosis (HR, 10.22; 95% CI, 2.94-35.50) were associated with worse outcomes.
Conclusions and Relevance
The findings of this review suggest that there is often a significant delay until the establishment of a correct diagnosis of childhood MF, which may be detrimental to the prognosis.