People homozygous for the Asp70His mutation are expected to have prolonged apnoea in response to succinylcholine or mivacurium, similar to people with the Asp70Gly mutation.
The clinically most important variant is atypical (D70G) BChE because people with this variant have 2 hours of apnea after receiving a dose of succinylcholine that is intended to paralyze muscles for 3-5 minutes.