The England and Nottinghamshire cricketer James Taylor has said his world is "upside down" after he was forced to retire due to a rare heart condition.
The 26-year-old batsman has been diagnosed with ARVC (arrhythmogenic right ventricular cardiomyopathy), an inherited condition caused by a change or mutation in one or more genes.
It means the right side of his heart fails to pump blood around his body properly and it can cause abnormal heart rhythms.
The condition is progressive, which means it will get worse over time, and there is a risk of sudden death.
The cricketer wrote on Twitter: "Safe to say this has been the toughest week of my life! My world is upside down. But I'm here to stay and I'm battling on! #lifestooshort."
ARVC is one type of cardiomyopathy. Another type is hypertrophic cardiomyopathy (HCM), which affects former Bolton Wanderers footballer Fabrice Muamba.
He collapsed on the pitch in 2012 and was also forced to retire early.
The charity Cardiac Risk in the Young (Cry) says 12 young people in the UK die of undiagnosed heart defects every week.
Dr Steven Cox, chief executive of Cry, said: "ARVC is a relatively rare condition, thought to affect between one in 1,000 and one in 5,000 people.
"ARVC often runs in families and several genes have been identified as causing the condition in these families but other factors that contribute to the disease can include viral infection, inflammation and endurance exercise."
Cry runs a screening programme which tests over 23,000 young people every year, aged 14 to 35.
Dr Cox said: "The vast majority of these screenings take place in the community, often testing young people involved in grass roots sport. However, Cry also works alongside most of the UK's professional sporting bodies and associations to provide regular testing for its elite athletes.
"Many sports now recommend routine testing for their elite athletes as some of the conditions that can cause young sudden cardiac death, including ARVC, can be 'acquired' or exacerbated by ongoing training and pressure exerted on the heart."
Not everyone diagnosed with ARVC develops symptoms but people suffer palpitations, light-headedness, fainting, breathlessness or an irregular heartbeat.
Other symptoms include swollen ankles or legs, and swelling in the abdomen.
Doctors aim to identify patients at risk of sudden death and start treatment straight away, such as using medicines to control the abnormal heartbeat or surgery to improve the function of the heart muscle.
The British Heart Foundation said up to one in 1,000 people are estimated to have a faulty gene which can lead to ARVC. This equates to around 64,100 people in the UK.
Christopher Allen, senior cardiac nurse at the charity, said: "ARVC is quite a rare inherited heart condition, which can increase your risk of having abnormal and sometimes dangerous heart rhythms.
"Tragically, the first sign that the condition is present can sometimes be when someone has a sudden cardiac arrest, and this can be at any age.
"There is currently no cure for ARVC, but it can be managed using medications and procedures, and for many people they can live a relatively normal life.
"In some cases, the risk of triggering a dangerous heart rhythm can be exacerbated by higher levels of physical activity, so these people may be advised to restrict what they do by their specialist."