Omalizumab in Infant Facial Mastocytoma: 36‐Month Efficacy and Safety Study

Segmental mastocytoma is a rare form of cutaneous mastocytosis. While most cases in children regress spontaneously, lesions in cosmetically and functionally critical areas like the face pose notable challenges due to refractory pruritus, flushing, blistering, and psychosocial distress [1]. Treatment options are limited, especially for infants. We report the novel use of omalizumab, an anti-IgE monoclonal antibody, in a toddler with segmental facial mastocytoma, highlighting sustained efficacy and previously unreported long-term safety data over 36 months. To objectively quantify and monitor treatment response, we employed the Scoring Mastocytoma (SCORMA) Index [2] (see Table 1). All longitudinal SCORMA assessments were performed by the same dermatologist, with the subjective component consistently reported by the patient's mother to ensure comparability. A 3-month-old male presented with erythematous, edematous plaques and blisters distributed along the right trigeminal (V1/V2) dermatome (Figure 1A). Histopathology confirmed mastocytosis (CD117+, Giemsa+). Systemic involvement was excluded. Initial management with oral cetirizine (0.25 mg/kg/day) and topical mometasone 0.1% once daily led to partial plaque regression and blister resolution by Month 9 (Figure 1B). However, severe pruritus (9/10) and recurrent flushing (3 episodes/week) persisted, causing considerable discomfort and parental concern regarding disfigurement. Given the suboptimal disease control despite conventional therapy, coupled with parental preference for aggressive intervention, omalizumab was administered based on its documented safety profile in infancy [3] and established efficacy in mastocytosis [4, 5]. For our 9-month-old patient, we adopted an intermediate dose of 150 mg monthly, bridging the gap between reported regimens of 100 mg/month in a younger infant (5 months) and up to 300 mg every 2 weeks in an older toddler (2 years) [3, 5]. After the second dose, a marked reduction in pruritus (3/10) and flushing frequency (0.5 episode/week) was observed. This response was sustained throughout the treatment course (Figure 1C: after 15 months of omalizumab, representing the period prior to the drug holiday). No new blisters or cutaneous atrophy occurred. A drug holiday at 24 months resulted in swift symptom rebound (Figure 1D), which resolved within 4 weeks of reinitiating omalizumab, with evident improvement noted by 36 months of age (Figure 1E). At the most recent follow-up (45 months of age), the patient exhibited substantial and sustained clinical improvement, with complete resolution of pruritus and a notable decrease in lesional surface area compared to baseline (Figure 1F). Symptom severity, as measured by the SCORMA Index and flushing frequency, was markedly reduced following treatment (see Table 1). No adverse effects on growth, ocular pressure, liver/renal function, or immune competence were observed throughout the 36-month treatment period. This observation provides critical insights into the management of severe segmental mastocytoma. First, it demonstrates that omalizumab can achieve rapid and sustained control of debilitating mediator-release symptoms in the youngest pediatric patients. Second, the symptom rebound upon withdrawal and subsequent recapture of efficacy upon rechallenge provide robust evidence of the drug's effect and the necessity for continued therapy in selected cases. Most importantly, we present novel 36-month safety data for omalizumab in a toddler, showing no negative impact on growth or organ function, thereby addressing a significant gap in the literature [4]. The case illustrates a paradigm of symptom-centric disease modification, where the goal is not necessarily lesion eradication but rather the prevention of complications and the preservation of quality of life during critical developmental years. While corticosteroids remain a first-line option, their long-term use on the face is limited by risks of atrophy and glaucoma. Omalizumab presents a potent steroid-sparing alternative. Our case underscores the potential of biologic therapy to modify disease course and mitigate psychosocial morbidity in severe infantile mastocytoma. Larger prospective studies are warranted to confirm these findings. The study was funded by the Beijing Hospitals Authority’s Ascent Plan (DFL20241201). The authors declare no conflicts of interest. The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.