Atopic dermatitis (AD) and ulcerative colitis (UC) are immune-mediated inflammatory diseases that may coexist, creating therapeutic challenges during biologic treatment. Here, we report a patient with long-standing AD and UC who was receiving ustekinumab therapy for UC and subsequently developed worsening eczema. In such cases, distinguishing an AD flare from a drug-induced eruption or secondary infection is a key clinical challenge because this distinction directly influences decisions regarding continuation or discontinuation of biologic therapy. Clinicopathologic evaluation supported the diagnosis of an AD flare rather than a drug-induced reaction. Temporary discontinuation followed by resumption of ustekinumab did not result in recurrence of cutaneous lesions, and the patient’s UC remained stable. In addition, we conducted a focused review of previously reported cases of patients with concurrent AD and UC treated with biologics or Janus kinase (JAK) inhibitors and summarized their clinical characteristics and outcomes. This report highlights clinical considerations when selecting biologic or targeted therapies in patients with coexisting AD and UC and underscores the importance of careful clinicopathologic assessment of cutaneous eruptions during biologic therapy.
Maeyama et al. (Thu,) studied this question.