Background  Infantile haemangioma (IH) has recently been reported as an aberrant proliferation and differentiation of a primitive mesoderm-derived haemogenic endothelium regulated by the renin-angiotensin system (RAS), leading us to propose angiotensin converting enzyme (ACE) as a potential therapeutic target.

Objectives  To present initial results of our open-labelled observational clinical trial using captopril, an ACE inhibitor (ACEi), in the treatment of problematic proliferating IH.

Methods  After initial screening investigations, infants with problematic IH were admitted for initiation of captopril with a 0·1 mg kg−1 test dose orally, followed by 0·15 8-hourly over 24 h. This was then followed by dose escalation to 0·3 mg kg−1 8-hourly for another 24 hours. The dosage was increased to 0·5 mg kg−1 8-hourly 1 week later, if a noticeable involution had not already occurred. The response of IH to captopril was documented clinically and photographically before and after treatment and any side-effect was recorded.

Results  Two boys and six girls aged 5–22 weeks (mean 12·9) with problematic IH were recruited with the lesions located in nasal tip (n 1), cervicofacial (n 3), periorbital (n 1) and perineal (n 2) areas, and shoulder (n 1). Transient mild renal impairment occurred in one subject but resolved spontaneously. No other complication was observed. The IHs in all patients responded to captopril at a dosage of 1·5 mg kg−1 daily which led to a dramatic response in three, moderate response in two, and slow response in three patients. Continued involution of IHs was observed during the follow-up period of 8–19 months (mean 15·8) in all subjects. Treatment was ceased at 14 months of age in seven patients with no rebound growth. In the remaining patient, rapid healing occurred with ongoing gradual reduction in the size and colour of a large ulcerated retroauricular lesion following 5·5 months of treatment. The lesion was excised to address its persistent distortion of the ear.

Conclusions  The response of IH to an ACEi supports a critical role for the RAS in IH and represents a paradigm shift in the understanding and treatment of this enigmatic condition.