Paediatric solar urticaria: a case series

Dear Editor, Solar urticaria (SU) is a rare photodermatosis occurring in response to exposure to ultraviolet (UV)A, (UVB), visible light and rarely infrared radiation. The condition typically affects adults (median age of onset 35 years),1 with only one report of SU occurring in a child (aged 2 years old).2 Here we present five cases of SU occurring in childhood. The group consisted of four male patients and one female patient (Table 1). The mean age of onset was 10·4 months (range 1 month to 2 years). Two patients were affected year round, while the remaining three were symptomatic in the spring and summer only. Two patients also reported sensitivity to fluorescent lighting. Onset times following exposure were < 10 min and the reaction lasted < 3 h in four of the children. The fifth patient's reaction was delayed (30 min), with a slower resolution up to 12 h. All sun‐exposed sites were affected in two patients, two had involvement of the hands and face, and one had facial involvement only. The patients’ medical histories PLE, polymorphic light eruption; NF1, neurofibromatosis type 1. The patients’ medical histories PLE, polymorphic light eruption; NF1, neurofibromatosis type 1. Noncutaneous features (sneezing, epiphora and cutaneous angio‐oedema without mucosal involvement) were reported in two patients. Drowsiness and reduced muscle tone immediately on sunlight exposure were confirmed in one following observed provocation; electroencephalogram and electrocardiogram in the absence of light were normal. Red‐cell porphyrins and lupus serology were negative in all patients. Monochromator testing was performed in four patients using a 450‐W xenon arc lamp linked to a Ninewells Phototherapy monochromatic light source (Bentham Instruments Ltd, Reading, U.K.). All were tested to 300 ± 5 nm (wavelength ± half‐maximum bandwidth), 310 ± 5 nm, 320 ± 10 nm, 340 ± 20 nm, 360 ± 20 nm, 380 ± 20 nm, 400 ± 20 nm, 500 ± 27 nm and 600 ± 27 nm. All four had weal and flare reactions to visible light (400–600 nm), occurring within minutes of exposure in three patients, and after 4 h in the fourth (the same patient who had a delayed onset and prolonged offset). Time for resolution ranged between 10 min and 12 h. Phototesting was not undertaken in one owing to spontaneous resolution. Following diagnosis all were advised on photoprotection. Due to the systemic manifestations in two, a transparent purple filter was identified that reduced the penetrance of urticating wavelengths (500–680 nm), and was attached to the respective pushchairs. This filter was manufactured for use in theatre lighting (deep purple colour effect lighting filter; Rosco Laboratories, Stamford, CT, U.S.A.). To our knowledge this is the first report of such a film being used in the management of any photodermatosis. All patients were treated with antihistamines. Four of the five children demonstrated significant improvement, with near complete resolution. Both cetirizine and fexofenadine were used successfully in separate children (four times the recommended dosage); chlorpheniramine and cetirizine were both successful at the recommended dose in a further two. One patient failed to respond to both cetirizine and loratadine (up to four times the recommended maximum dose) when used with the leukotriene receptor antagonist montelukast, and H2 receptor blocker ranitidine. Subsequently, inhaled sodium cromoglycate 10 mg four times a day was partially effective. In two children, spontaneous resolution occurred before the age of 3 years (2 years and 3 months, 20 months after onset; and 2 years and 11 months, 34 months after onset). In the remaining three the disease remains active although controlled (now aged 4·6, 5·1 and 8·75 years). SU accounts for < 10% of patients presenting to photodermatology centres in the U.K.3 It is considered a disease of adulthood, with a mean age of onset between 26 and 41 years in cohort studies.1,3,4,5 There are very few published reports of SU in children. In 1997, Harris et al. reported on a 2 year old with SU.2 The patient was photosensitive from a few weeks of age and was sensitive to wavelengths of 305–500 nm. Cohort studies have included paediatric cases, but they have not been described individually.1,3,4,5,6,7 The characteristics of SU in our series are similar to those reported in large adult cohorts. Using Beattie et al. as a comparison,1 the onset times in our group were 10 min in four of the five children (adults: 77% within 15 min) and they resolved in all children by 24 h (adults: 95%). Two children were affected year round in comparison with 68% of adults. Visible light alone was responsible for SU in all children. In total 93% of adults were sensitive to visible light, but often in combination with UVA (31% visible light alone). The response rate to antihistamines (80%) in our series was comparable with that in adults (66%). We present the first series of SU arising in children. The presentation of SU in children is similar to that in adults, and it generally responds to antihistamine therapy. Funding sources: none. Conflicts of interest: none to declare