CD28 Allergic contact dermatitis to tetracaine (Ametop®) at a subcutaneous port-a-cath site in a child

Abstract

Topical local anaesthetics are widely used in children to facilitate access to indwelling vascular access devices. Subcutaneous vascular access ports are becoming increasingly popular for paediatric oncology patients for their discrete appearance. Although allergic contact dermatitis (ACD) to ester-type local anaesthetics is well known, it is important to recognize its presentation with subcutaneous vascular access ports to prevent misdiagnosis. A 6-year-old girl was diagnosed with an optic nerve glioma and began receiving regular vinblastine chemotherapy through a subcutaneous port-a-cath. A possible cutaneous adverse drug eruption was suspected. On examination there was a well-demarcated eczematous weepy dermatitis patch at the port-a-cath entry site. As it was a striking and unusual dermatosis, differentials included infection and infiltrative skin disorders such as leukaemia cutis. On further history taking it was noted that the child was having Ametop® (tetracaine) applied to the area over the port-a-cath prior to administration of the vinblastine intravenous injection. A diagnosis of Ametop-associated contact dermatitis was considered. The patient was advised to stop Ametop® and use Fucibet (fusidic acid 2% with betamethasone valerate 0.1%) to treat the area. A patch test to Ametop (tetracaine 4%) and Emla (lidocaine 2.5% with prilocaine cream 2.5%) was performed, confirming positivity to Ametop on reading at day 4. Further testing with local anaesthetic series demonstrated a positive reaction to caine mix III (benzocaine, dibucaine and tetracaine) and a negative reaction to caine mix IV (amylocaine hydrochloride, lidocaine and prilocaine), supporting sensitization to ester-type local anaesthetics, consistent with tetracaine allergy. The patient was switched to Emla as a topical local anaesthetic, the skin improved markedly, and she continues with regular chemotherapy. Allergic contact dermatitis to topical local anaesthetics should be included in the differentials for localized dermatitis in paediatric patients with subcutaneous venous access devices. Amide-type local anaesthetics, such as lidocaine, may represent safer alternatives in the future.