The fight was on the undercard of the WBC Super Featherweight title fight between Francisco Vargas and Miguel Berchelt.
After a slow opening round, Melikyan pushed forward to land jabs and over hand rights against Portillo, who tried to box from the outside.
Portillo, who came into the fight with an undefeated record and fought on the A-side of the corner, was on his back foot for most of the fight.
By Rounds 3 and 4, it was clear that Portillo was being worn down, and Melikyan landed more counter hooks and right hands, even hurting Portillo in both rounds.
However, the judges did not see it the way many in attendance at the Fantasy Springs Casino saw it, and awarded Portillo the MD victory.
Judges Jerry Cantu and Fernando Villarreal scored it 37-39, while Rey Danseco scored it a 38-38 draw.
Disgusting scorecards to say the least, but Melikyan will be back and stronger than ever.