Introduction: Lichen planus pemphigoides (LPP) is a rare acquired autoimmune disease characterised by the evolution of subepidermal blisters on normal and lichen planus affected skin. Case summary: We describe a case of lichen planus pemphigoides in a 54-year-old Chinese woman. The patient presented initially with scaly psoriasiform plaques and was diagnosed to have guttate psoriasis. She was treated with narrowband ultraviolet (NBUVB) therapy twice weekly. Within a month of starting phototherapy, she experienced a flare up of her skin lesions with a generalised eruption of violaceous papules, tense bullae over the lower limbs as well as Wickham’s striae over the buccal mucosa. Histology of the violaceous papule over abdomen revealed interface dermatitis, while the specimen from a blister showed subepidermal bulla with linear deposition of IgG and C3 along the basement membrane zone. A diagnosis of LPP was made on clinicopathological grounds. The patient subsequently responded well to oral prednisolone at a dose of 0.5 mg/kg/day. Conclusion: This is the first case report of NBUVB alone unmasking LPP. In the presentation, we will describe the pathological mechanism of NBUVB in the development of LPP and the key features distinguishing LPP from bullous lichen planus (BLP), psoriasis and bullous pemphigoid (BP).

INTRODUCTION: Cast immobilisation remains the mainstay of treatment for various fractures in paediatric patients, yet patients commonly complain of skin irritation and discomfort. This study aimed to perform a qualitative and quantitative evaluation of the effects of cast immobilisation on the skin of children and adolescents. MATERIALS AND METHODS: Patients aged 6-17 years of age with a fracture treated in a fiberglass short-arm or short-leg cast were recruited. Transepidermal water loss (TEWL), stratum corneum (SC) hydration, hair density and presence of any skin signs were assessed before and after cast. Patients were required to complete a weekly questionnaire to rate itch, malodour, warmth, and dampness of the skin under the cast. RESULTS: A total of 60 subjects completed the study. Thirty-six patients received a short-arm cast; 24 received a short-leg cast. Upon cast removal, TEWL was significantly increased on the volar surface of the arms and legs ( <0.05), and the dorsal surface of the arm ( <0.05). Likewise, SC hydration was significantly increased at most sites ( <0.05), except the volar surface of the leg ( = 0.513). There was no change in hair density. Throughout the duration of casting, there was an increase in itch and malodour scores. CONCLUSION Moderate but significant changes in TEWL, SC hydration and subjective symptoms were observed during the duration of cast immobilisation, demonstrating that cast immobilisation for up to 4 weeks exerts moderate adverse impact on patients' skin. Further studies to explore the use of better materials for cast immobilisation to improve skin barrier function and overall patient satisfaction are warranted.