BI27 Treatment of recalcitrant eczema in a patient with B-cell and natural killer cell lymphopenia of unknown cause

Abstract We present a case of recalcitrant eczema in a patient with B-cell and natural killer (NK) cell lymphopenia of unknown cause. A 53-year-old man was referred to the dermatology clinic with a 6-month history of an itchy erythematous rash, starting on his chest and arms and spreading to involve his back and legs. This was causing significant disruption to sleep and work. He had tried superpotent topical corticosteroids and oral prednisolone, as well as emollients, none of which had improved his symptoms. He had no personal or family history of skin disease. He had been well without a significant medical history until 7 years ago, when he had developed recurrent chest infections and an episode of confirmed multidermatomal shingles. On examination, he was suberythrodermic with a widespread erythematous, polymorphic rash that was eczematous in some areas but raised and annular in others. Initially, we were concerned about mycosis fungoides; however, Sézary cells were not detected on flow cytometry and skin biopsies demonstrated findings consistent with atopic dermatitis. We conducted lymphocyte subset testing because of his atypical infection history, which demonstrated complete absence of B cells and low NK cells (0.02 × 109 cells L−1). He had low IgM and IgA levels, but normal IgG levels. We therefore treated him as having eczema and additionally referred him to the immunology team. Initial treatment with mometasone ointment was then escalated with clobetasol propionate and tacrolimus 0.1%, but with no beneficial effect. Narrowband ultraviolet B therapy over 3 months also did not improve his symptoms. He was investigated by the immunologists, who were unable to find any cause for his lymphopenia. He had normal Bruton tyrosine kinase expression, a myeloid gene panel did not detect mutations in GATA2 and UBA1, and whole-genome sequence analysis did not identify any pathogenic variant(s) that could explain the cause of his clinical presentation. He had no history of prior immunosuppressive treatment and no evidence of thymoma on computed tomography imaging. As his eczema was refractory to both topical treatments and phototherapy, we wanted to start systemic treatment but were limited with options that would not further compound his immunosuppression. Tralokinumab was trialled for 12 weeks, as this has a single therapeutic target (interleukin-13), but unfortunately there was no improvement. Following discussion with the immunologists, he was commenced on upadacitinib as this was felt to have a more targeted immunosuppressive effect above agents such as methotrexate and dupilumab. We await his next follow-up appointment to assess response. This case highlights the complexity of treating an immunocompromised individual with immunosuppressive agents, when the cause of their immunosuppression is unknown.