Nadia, 25, is one of hundreds of young microcephalics -- people born with small skulls and protruding noses and ears because of a genetic mutation -- who can be found on the streets of Gujrat, in central Punjab province.
Officials say many of them have been sold off by their families to begging mafias, who exploit a tradition that the "rat children" are sacred offerings to Shah Daula, the shrine's 17th century Sufi saint.
"These are God's children. We are proud to look after her," said Ijaz Hussain, the shrine's government-employed custodian, as Nadia shrieked unintelligibly and put coins in a battered wooden box at her side.
According to local legend, infertile women who pray at Shah Daula's shrine will be granted children, but at a terrible price. The first child will be born microcephalic and must be given to the shrine, or else any further children will have the same deformity.
Hussain said Nadia was just a young child when she was dumped at the shrine 20 years ago in the dead of the night. Her parents were never traced, he says.
"Since that day we have taken care of her, she is like family to us. People come here for prayers and seek fulfilment of their desires but they are respectful towards her," added Hussain, 56.
Pakistan's government says it has tried to crack down on exploitation of the "chuhas" (Urdu for rats) and says it plans to set up a shelter in Gujrat to rehabilitate them.
The shrine stopped officially accepting microcephalics in the 1960s when the government took over the site.
But not only does it still keep Nadia at its gate, the town's beggar masters also keep the superstition alive.
"Get lost! I don't want to talk to you," shouted a bearded beggar master in Gujrat's main bus station, grabbing a microcephalic woman by the hand and leading her through the crowds when asked to comment on his actions.
Bus passengers gave the woman money, as many believe it is bad luck not to.
Another microcephalic man stood with his handler in the wilting afternoon heat, staring into space.
The high incidence of microcephalics in Gujrat, an industrial city of around one million people, has long been a bone of contention.
The popular belief among many Pakistanis -- that cruel beggar gangs clamp the children's heads in infancy -- is strongly denied by government and advocacy groups, who say there is no evidence to support this.
Recent medical studies say the most likely cause is that the normally rare recessive genes behind many microcephaly cases crop up with greater frequency because of the common custom of marrying cousins in Pakistan.
But finding the cause is easier than stamping out the exploitation of "rat children" in the name of religion, says Pir Nasiruddaula, a descendant of the saint who has written several books on the shrine.
"The myth of the chuhas has been exploited by beggar mafias and religious groups," said Nasiruddaula, a former science professor in his 70s.
"They roam the villages and if the real chuha is born they give them some money and they take them," he said.
"But what kind of saint would really curse issueless women with the 'blessing' of deformed children?"
Rakhshan Sohail, of the Punjab provincial government's Child Protection and Welfare Bureau, said his department planned to establish a centre in Gujrat to stamp out exploitation of microcephalics.
"Some of these children, the handicapped ones especially, are accompanied by relatives," he told AFP. "But begging gangs also look for poor parents who will sell them because they are a burden to feed and shelter."
Sohail said his department had busted more than 30 gangs across the province involved in exploiting street children, some of which had broken the limbs of children so that they would earn more as beggars.
But the "rat children" are symptomatic of hardships faced by up to 100,000 street children nationwide -- and an economic crisis caused by spiralling fuel and food prices is hurting his department's efforts, he said.
"It's a critical issue," he said. "When people are living on less than a dollar a day, they are more likely to put their children on the roads and make them beg."