This aggregation is stronger in BII phobia than in any other known phobic disorder: upwards of 60% of those with the phobia have first-degree relatives who are also BII-phobics. It is believed that this evidences the phobias genetic underpinnings. One study estimated actual heritability of the phobia at 59%.Additionally, a majority of phobics attribute their fear to environmental factors. For instance, some sort of traumatic event involving blood, injury, or injection that conditioned them to fear those particular stimuli. Others self-report being conditioned by seeing another person react to the stimuli with a consistent pattern of fear.It has been theorized that exhibiting vasovagal response when exposed to blood was evolutionarily advantageous, and that this phobia is a vestige of an ancestral evolutionary mechanism. Fainting may have acted as a form of tonic immobility, allowing primitive humans to play dead in a situation where blood was being spilled, perhaps helping them to avoid the attention of enemies. It has also been suggested that the drop in blood pressure associated with seeing blood — as with an individual seeing blood from their own wound — occurs in order to minimize blood loss. Treatments
Individuals typically seek therapeutic treatment for BII phobia in a bid to alleviate symptoms that arise when exposed to a phobic trigger.
See also
Methylmalonic acidemia
Organic acidemia

Notes
The term combined malonic and methylmalonic aciduria with the suffix -uria (from Greek ouron, urine) has become established in the scientific literature in contrast to the other term combined malonic and methylmalonic acedemia with the suffix -emia (from Greek aima, blood). However, in the context of CMAMMA, no clear distinction is made, since malonic acid and methylmalonic acid are elevated in both blood and urine. References
External links
Combined malonic and methylmalonic acidemia at Orphanet