Adrian Wojnarowski of ESPN provided the full statement from Fultz's agent, Raymond Brothers.
"Markelle has been diagnosed with neurogenic thoracic outlet syndrome, a physical injury," Brothers said. "TOS affects nerves between the neck and shoulder resulting in abnormal functional movement and range of motion, thus severely limiting Markelle's ability to shoot a basketball. TOS is treatable by physical therapy."
"People were saying it was a mental problem and it is not," Brothers added, per Wojnarowski. "There's no way you're the No. 1 pick in the world and all of a sudden you aren't able to consistently raise your arms to shoot. ... Something is physically wrong. Now we have the answer to that problem."
The Sixers confirmed the TOS diagnosis and stated "further updates will be provided as appropriate."
Charania added Fultz has traveled to see specialists throughout the country and provided more details about the recovery plan:
Fultz has missed Philly's last six games while receiving medical opinions on his right shoulder, which limited him to 14 regular-season appearances as a rookie last year.
The 20-year-old Maryland native averaged 8.2 points, 3.7 rebounds and 3.1 assists while shooting only 41.9 percent overall and 28.6 percent from three-point range in 19 games this season. During his one season in college with the Washington Huskies, Fultz shot 41.3 percent from deep.
His shooting woes led him to test out a few curious tactics, including juggling the ball at the free-throw line, in an effort to break out of the slump:
McCollum and the Blazers Snapped Postseason Losing Streak for "Jennifer"
Stars Invest in Plant-Based Food as Vegetarianism Sweeps NBA
The NBA Got Some Wild Techs This Season
Jarrett Allen Is One of the NBA’s Hottest Rim Protectors
Wade's Jersey Swaps Created Epic Moments This Season
Westbrook Makes History While Honoring Nipsey Hussle
Devin Booker Makes History with Scoring Tear
29 Years Ago, Jordan Dropped Career-High 69 Points
Bosh Is Getting His Jersey Raised to the Rafters in Miami
Steph Returns to Houston for 1st Time Since His Moon Landing Troll
Lou Williams Is Coming for a Repeat of Sixth Man of the Year
Pat Beverley Has the Clippers Stealing the LA Shine
LeBron Keeps Shredding NBA Record Books
Young's Hot Streak Is Heating Up the ROY Race with Luka
LeBron and 2 Chainz Form a Superteam to Release a New Album
Wade's #OneLastDance Dominated February
Warriors Fans Go Wild After Unforgettable Moments with Steph
Eight Years Ago, the Nuggets Traded Melo to the Knicks
Two Years Ago, the Kings Shipped Boogie to the Pelicans
ASG Will Be Competitive Again If the NBA Raises the Stakes
Last week, Woj reported Fultz's Sixers teammates had become "increasingly concerned about his overall well-being" amid the "internal and external debate about how much of this perplexing circumstance is physical versus mental."
Meanwhile, Keith Pompey of the Philadelphia Inquirer reported sources believe the 76ers have grown "tired of this saga" and have considered trading the first overall pick of the 2017 draft.
The Sixers will likely have to put those plans on hold until Fultz finishes his rehab and returns to the floor, though.