Background: Growing patients with nasopharyngeal carcinoma (NPC) were treated with intensity-modulated proton therapy (IMPT). However, a high probability of severe acute radiation dermatitis (ARD) was observed. The objective of the study is to investigate the dosimetric parameters related to ARD for NPC patients treated with IMPT. Methods: Sixty-two patients with newly diagnosed NPC were analyzed. The ARD was recorded based on the criteria of Common Terminology Criteria for Adverse Events version 4.0. Logistic regression model was performed to identify the clinical and dosimetric parameters related to ARD. Receiver operating characteristic (ROC) curve analysis and the area under the curve (AUC) were used to evaluate the performance of the models. Results: The maximum ARD grade was 1, 2, and 3 in 27 (43.5%), 26 (42.0%), and 9 (14.5%) of the patients, respectively. Statistically significant differences (p < 0.01) in average volume to skin 5 mm with the respective doses were observed in the range 54–62 Cobalt Gray Equivalent (CGE) for grade 2 and 3 versus grade 1 ARD. Smoking habit and N2-N3 status were identified as significant predictors to develop grade 2 and 3 ARD in clinical model, and V58CGE to skin 5 mm as an independent predictor in dosimetric model. After adding the variable of V58CGE to the metric incorporating two parameters of smoking habit and N status, the AUC value of the metric increases from 0.78 (0.66–0.90) to 0.82 (0.72–0.93). The most appropriate cut-off value of V58CGE to skin 5 mm as determined by ROC curve was 5.0 cm³, with a predicted probability of 54% to develop grade 2 and 3 ARD. Conclusion: The dosimetric parameter of V58CGE to skin 5 mm < 5.0 cm³ could be used as a constraint in treatment planning for NPC patients treated by IMPT.

In addition to Pseudomonas aeruginosa, other organisms including Staphylococcus aureus have been reported to have associations with ecthyma gangrenosum (EG). There are very limited reports of Staphylococcus aureus EG causing systemic symptoms in an immunocompetent child. We present the case of an atopic child with transient neutropenia developing characteristic skin lesions of EG. Culture of the skin wounds yielded methicillin-susceptible Staphylococcus aureus (MSSA), and incisional biopsy of the skin lesions revealed aggregates of Gram-positive cocci at the subepidermal area and necrotic vasculitis but without perivascular bacterial invasion. In the literature review, seven cases of Staphylococcus aureus EG were reported, and only two were pediatric cases. From this case, we emphasize the importance of early culturing for microorganisms in cases presenting with EG. When toxin-mediated systemic symptoms accompany EG-like skin lesions, MSSA should be considered in an atopic child with transient neutropenia.