Specialist examinations found the condition followed a period of excessive physical strain and weight loss linked to a gastrointestinal illness the 17-year-old had picked up before pre-season training began. Leverkusen say the teenager will begin inpatient treatment at a specialist facility in the coming weeks, with an individually tailored sporting build-up programme to follow once that phase of his recovery is complete. The club has not given a timeframe for his return.
Eichhorn joined Leverkusen from Hertha BSC this summer in a deal reported at around €9m, having made 19 appearances for Hertha's first team in 2. Bundesliga last season at the age of 16, a run that made him one of German football's most closely watched young talents and drew interest from several clubs across Europe before his move to the BayArena.
Sporting director Simon Rolfes said the club's focus for now is on giving the player the space to recover without added pressure: "Kennet is facing what we hope will be a very long career at the highest level.
"We will support him in the best possible way on that path.
"What matters at this point is that we have put the right measures in place for his recovery, and that Kennet gets the time and calm he needs for his treatment, without pressure."
The diagnosis follows a similar case involving Germany World Cup winner Mario Götze, who was found to have a metabolic disorder in February 2017 shortly after returning to Borussia Dortmund from Bayern Munich — a reminder that, while serious, the condition need not derail a player's long-term career if managed properly.