Lesbos, Greece - Mohammed, two years and eight months old, has been living in the Moria refugee camp in Greece, for four months with a life-threatening condition and limited access to healthcare.

He was born prematurely with hydrocephalus, a blockage of the circulation of fluid around the brain resulting in increased pressure in the skull, which can cause brain damage.

In the arms of his mother, 26-year-old Fawzia Ahmadi, he wriggles as she attempts to soothe him.

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The family of four, including a one-year-old girl, live in a small tent at the top of an olive grove, which is acting as an overspill for the refugee camp, now close to a population of 20,000 people as of January.

It was designed to hold no more than 3,000.

They came here via Turkey, fleeing the continued unrest in their home in Kabul, Afghanistan.

"It's very difficult in the night," Ahmadi said. "He complains of headaches a lot and so we take it in shifts to sleep and check that he is OK. I worry about him so much.

"I've been told that I need to keep him clean but I don't know how I can do that here? We cannot wash him every day, the weather is very cold and so is the water."

Ahmadi said she understands that the local hospital cannot cope with her son's needs.

"I think it's not their problem because there are too many sick people there. My son is sick but there are already too many kids who are sick, they don't have the time to take care of them all. I just want him to be somewhere warm where I can wash him and take care of him."

Mohammed is just one of at least 140 children in the camp who have chronic, complex and life-threatening diseases who MSF (Doctors Without Borders) are deeply concerned about.

The organisation says they are being denied access to adequate medical care.

Left to right - Mohammed Ahmadi, Fawzia Ahmadi, Hassan Ahmadi and their one-year-old daughter in Moria [Katy Fallon/Al Jazeera]

In July 2019, the Greek government rescinded access to healthcare for asylum seekers and undocumented people living in Greece, leaving around 55,000 people without medical care, according to MSF.

George Makris, the assistant medical coordinator in Greece and the north Balkans for MSF, told Al Jazeera regarding Mohammed's case: "We don't have the resources to investigate this kind of medical condition and we don't have the specialised doctors who are paediatric neurologists either.

"At the same time, not even the hospital on the island of Lesbos has a paediatric neurologist and they do not have the diagnostic tools necessary to investigate this kind of condition."

Makris said that MSF doctors believe a device put in to help alleviate pressure could be malfunctioning, which is why Mohammed is having severe headaches.

"We are extremely worried about the complications that this malfunction could have, which could be life-threatening to this child," he said.

MSF is calling for the immediate transfer of children like Mohammed from the camp to hospitals in the mainland.

Access even to urgent healthcare in the Moria refugee camp is challenging. The local hospital is around 10km away, ambulances are not always readily available and most families cannot afford the taxi fare there.

Makris told Al Jazeera that the local hospital is overwhelmed.

"They have to cover 20,000 more people here without the proper equipment and humanitarian resources," he said. "For us as doctors, it's extremely difficult to examine and treat children with severe physical or mental disabilities and send them back to a camp that is unsafe and overcrowded where they live in summer tents in the middle of winter. It's tragic."