Letter To The Editor Mycophenolate mofetil in the treatment of childhood pemphigus vulgaris Roberto Antonucci, 1 Cristian Locci, 1 Gabriele Biondi, 2 Alessandra Manconi, 1 Rosanna Mannazzu, 1 Lidia Abis, 1 Federica Sucato, 2 Rosanna Satta, 2 Amelia Lissia 3 and Maria Antonietta Montesu 2 1 Pediatric Clinic, 2 Dermatology and 3 Pathological Anatomy, Department of Medical, Surgical and Experimental Sciences, University of Sassari, Sassari, Italy Dear Editor, We read with great interest the article by Terashita and colleagues 1 in a recent issue of Pediatrics International (September 2019). The authors successfully treated with mycophenolate mofetil (MMF) and prednisolone a 12-year-old boy affected by Behcet’s disease (BD). This is a recurrent sys- temic inflammatory disorder of unknown origin, presenting with oral and genital lesions, and cutaneous manifestations. Pemphigus is a group of autoimmune blistering disorders that is due to the loss of keratinocyte cell-to-cell adhesion in the epidermis caused by circulating autoantibodies against desmosomal proteins. Behcet’s disease and pemphigus share some characteristics, including extreme rarity in childhood, a chronic activation of the immune system and tissue inflammation, and involvement of skin. 1-4 Currently, autoinflammatory and autoimmune diseases might be considered as a single spectrum of disorders, with pure autoinflammatory diseases at one end and pure autoim- mune diseases at the other. Based on current evidence, BD is at the crossroad between autoinflammatory and autoimmune disorders. 5 In both BD and pemphigus, autoinflammatory and autoimmune mechanisms can coexist, with the former prevail- ing in BD and the latter in pemphigus. 4 Furthermore, BD and pemphigus are usually treated with systemic corticosteroids and a number of steroid-sparing agents. Herein, we report a case of a 9-year-old boy admitted to the hospital for the occurrence of multiple skin and mucosal blisters in the previous 2 months. On examination, skin lesions in different stages of evolution, including flaccid vesicles, blis- ters, erosions, and multiple crusted lesions, were predomi- nantly observed on the scrotum and the upper back (Fig. 1a, 1b), with a positive Nikolsky’s sign. Some painful erosions on the oral mucosa were also observed. Laboratory tests were negative, but anti-desmoglein (Dsg) 1 and anti-Dsg3 antibodies were both increased (196.57 RU/ml and 349.00 RU/ml, respectively). Histological examination of skin biopsy specimens showed intraepidermal suprabasal acantholysis and lymphoplasmacel- lular infiltrate in the superficial dermis. Direct immunofluores- cence revealed the positivity of keratinocytes for IgG and C3. Based on clinical, histological, and laboratory findings, the diagnosis of pemphigus vulgaris (PV) was made, and oral prednisone therapy (2 mg/kg/day) was started. After 2 weeks, only a partial clinical response was observed, therefore dap- sone was added to existing treatment. This medication led to complete resolution of mucosal lesions and partial regression of skin lesions, but, after 3 weeks, it was discontinued because of increased MetHb levels. Subsequently, one month of treat- ment with azathioprine, three courses of intravenous immunoglobulin, and three cycles of rituximab, performed in sequence, were all ineffective. Due to clinical severity and poor response to conventional treatment, MMF was started at a maximum dosage of 1200 mg/day (1200 mg/m 2 /day), along with prednisone 5 mg/day. At the 8 month follow up, excel- lent disease control and no side effects were documented. Complete disease remission was achieved 5 months after ther- apy discontinuation. Only 46 cases of childhood PV (onset age range, 1.5– 12 years), including the present case, have been reported in the literature. Mycophenolate mofetil has been used success- fully by Baratta et al. 6 , obtaining durable remission. It should Correspondence: Roberto Antonucci, MD, Pediatric Clinic, Department of Medical, Surgical and Experimental Sciences, University of Sassari, Viale san Pietro 12, 07100 Sassari, Italy. Email: rantonucci@uniss.it Received 16 April 2020; revised 14 May 2020; accepted 29 May 2020. a b Fig. 1 (a) Bullous lesions in the genital area. (b) Scaly crusted erosions on the upper back. © 2020 Japan Pediatric Society Pediatrics International (2020) 62, 1123–1124 doi: 10.1111/ped.14327