PA03 Chronic urticaria associated with systemic symptoms caused by tetrahydrocannabinol use in an adolescent

Abstract

We present the case of a 14-year-old boy with a 10-month history of recurrent fevers up to 41 °C lasting up to 3 days, associated with chronic urticaria affecting the torso, limbs and neck with intermittent coryzal symptoms. The eruption was characterized by transient weals exacerbated by heat and water exposure, partially responsive to antihistamines and self-resolving within 2 h. This was complicated by episodes of syncope, lethargy and intermittent diffuse abdominal pain. He was otherwise well in himself and attended boarding school. Inflammatory markers were only mildly elevated and there was a normal erythrocyte sedimentation rate. Autoimmune, viral, connective-tissue screen, thyroid function and complement levels were normal. Genetic testing did not identify any likely pathogenic variants. Following 10 months of persistent symptoms, a urine drug screen was performed and was positive for cannabinoid use. Cannabis use and vaping were then disclosed during the consultation without a parent present. The patient had previously denied recreational substance use with the paediatric team. There was complete resolution of symptoms following cessation, with no recurrence during follow-up appointments. Recurrent fever with urticarial eruptions, coryzal symptoms and episodic abdominal pain in an adolescent presents a broad diagnostic challenge, encompassing infectious, immune-mediated, autoinflammatory and malignant aetiologies. Drug-related causes may be under-recognized in this population, particularly when substance use is not routinely disclosed. Although cutaneous adverse reactions to cannabis have been described, concomitant cyclical fevers with coryzal symptoms and abdominal pain are poorly characterized. This case highlights cannabis use as a potential trigger and, given the increasing use in adolescents, should be considered in the evaluation of systemic and cutaneous symptoms of unknown aetiology. Accordingly, confidential consultations without next of kin present in the consultation room can open up further areas of interest and are important in adolescent dermatology to obtain accurate exposure history.