After a qualifying screening period, the PK, safety/tolerability, and efficacy of treatment with SC icatibant will be evaluated in at least 20 subjects (10 prepubertal and 10 pubertal/postpubertal subjects) who present with cutaneous, abdominal, or laryngeal symptoms of an acute attack of HAE. The PK and safety/tolerability of SC icatibant will be evaluated in at least 10 additional pubertal/postpubertal subjects who meet screening criteria and receive treatment with SC icatibant in the absence of a current acute HAE attack.