A teenager labelled a "fussy eater" by his parents has gone blind after only eating a diet of junk food for more than a decade, doctors have revealed.
The boy was first seen by his local GP when he was 14 after complaining of tiredness. He had a normal BMI and took no medications but tests showed macrocytic anemia - a type of anemia that causes unusually large red blood cells - and low vitamin B12 levels, which are needed to make red blood cells that carry oxygen around the body. He was given vitamin B12 injections and dietary advice.
Doctors were baffled a year later when the boy developed sensorineural hearing loss, a type of hearing loss arising from problems in the inner ear or cochlea, as well as vision symptoms, as they could find no cause.
By the age of 17, the boy's vision had become progressively worse, to the point of blindness. He confessed that since primary school, he had avoided foods with certain textures and had lived on a diet of French fries, Pringles, white bread, processed ham and sausages.
By the time his condition was diagnosed, the teenager had permanently impaired vision, which doctors blamed on his junk food diet. He also had vitamin B12 deficiency, low levels of copper, a high zinc level, and markedly reduced vitamin D level and bone mineral density.
Researchers from the Bristol Eye Hospital publish the extraordinary case report in the Annals of Internal Medicine. They recommend that doctors should consider nutritional optic neuropathy - a dysfunction of the optic nerve usually caused by drugs, or poor diet combined with alcoholism and smoking - in any patient with unexplained vision symptoms and poor diet, even in patients with a normal BMI.
The condition, which is so rare in developed countries, is potentially reversible if caught early. But if left untreated, it leads to permanent blindness.
Doctors also warned there could be an increase in similar cases given the popularity of ‘junk food’ at the expense of more nutritious options, and the rising popularity of veganism if the vegan diet is not supplemented appropriately to prevent vitamin B12 deficiency.
Dr Denize Atan, the study’s lead author, said: “Our vision has such an impact on quality of life, education, employment, social interactions, and mental health. This case highlights the impact of diet on visual and physical health, and the fact that calorie intake and BMI are not reliable indicators of nutritional status.”