Dhaka: A four-year-old Bangladeshi boy suffering from a mysterious illness that makes him look like an old man has been admitted to hospital for tests, doctors and his family said.

Doctors at a top hospital in Dhaka have agreed to try to diagnose and treat Bayezid Shikdar, who comes from a poor farming family, for free after learning of his plight on the weekend.

Born with excess skin that hangs from his limbs and face causing it to sag, Bayezid also suffers from related heart, vision and hearing problems.

His father, Lablu Shikdar, said numerous doctors have been at a loss to explain his condition.

"We sold our land to treat him at local hospitals. We took him to religious healers and herbal doctors, but his condition did not change. This hospital is our last hope," Shikdar told AFP at Dhaka Medical College Hospital this week.

"We hope they'll make him look like any other normal child."

Doctors initially suspected he suffered from progeria which causes rapid and premature ageing shortly after birth, leading to severe health complications.

The extremely rare genetic disorder was the subject of Hollywood movie "The Curious Case of Benjamin Button" starring Brad Pitt.

But doctors at the Dhaka hospital expressed caution, saying extensive tests were needed.

"In progeria, the ageing process accelerates with time," Abul Kalam, head of the hospital's burns and plastic surgery unit, told AFP on Monday.

"But Bayezid's parents have said the ageing of their boy has been halted recently. He has shown signs of improvement.

"We're investigating his condition. In addition to loose skin, he has problems in his heart, ear, eyes and penis."

Doctors said his genetic condition may also be the result of inbreeding, with marriage among relatives including first cousins common in Bangladesh's rural areas.

Bayezid's mother, Khatun, stressed that her son was just like any other child.

"He is very fond of fish and rice. He plays football and hide and seek with his cousins," she told AFP after her son's case was highlighted in Bangladesh media on the weekend.

"When I first saw him he looked like a bundle of skin. We had no idea what he was afflicted with. We thought the condition would go away soon."

"He is an extremely talented boy. There are days he grabs books and wants to go to school. But we thought he's still too young."

Doctors at the same hospital have also been treating a 26-year-old father dubbed "Tree Man" for the rare and massive bark-like growths on his hands and feet.