Hi, I looked around to try and help and found a few things, but unfortunately nothing definitive. First off, it's most commonly called "lean NAFLD" or "non-obese NAFLD".
Apparently, the cause is not understood, but there is probably a genetic component. Do you happen to be Asian?
Have you eliminated all fructose from your life? That would include all sugary drinks and all sweets, whether they have high fructose corn syrup or table sugar. Even things like pasta sauce. Fructose might make your condition worse, which isn't a surprise.
How is your waist size? Fat around the middle is not just ordinary fat and would be bad. Do you exercise? How much?
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I'll leave these URLs here for possible use.
"Fatty liver without a large “belly”: Magnified review of non-alcoholic fatty liver disease in non-obese patients"
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5561430/
2017
https://www.medscape.com/viewarticle/868783_4
by William F. Balistreri, MD
2016
Here is a storage disease that can affect even very young children: Lysosomal Acid Lipase Deficiency
https://www.liverfoundation.org/for-patients/about-the-liver/diseases-of-the-liver/lysosomal-acid-lipase-deficiency/
How do your cholesterol tests turn out?
You have a specific problem and nobody on this website is a medical professional. What I would suggest, if you haven't already done so, is, if you're able to travel and can pay for it, is to go to places that specialize in finding answers to difficult conditions. You've probably heard of some of them -- John's Hopkins, Mayo Clinic, Cleveland Clinic and many top university hospitals -- made their reputation by going deeper than the average docs do, even the average specialists. I would tell you to stop the milk thistle, though -- milk thistle isn't recommended to be taken on a regular basis. It's mostly used when you're trying to clean something out of the liver. There are natural remedies that do support the liver and can be taken more regularly -- artichoke, for example, is specific for the fat digestion action of the liver and gall bladder -- and of course the main antioxidant protecting the liver, glutathione, is very high in wheat grass. Sometimes taking milk thistle for long periods of time can make medication wash out too quickly or nutrients wash out too quickly. You don't want to liver cleanse in your situation, you want to liver strengthen, as you're already eating in a way that might be depriving you of essential nutrients. Other than that, though, you really need to talk to the best medical professionals, and they aren't here, unfortunately. It's possible there is a forum on this website specifically devoted to liver problems, though, and you might find something in the archives if there is that gives you some enlightenment. I hope you do find the answer, this must be very tough to handle.
To Faith0Swan: if you read this thread I will be happy to discuss any or all of that above with you. For example, the one link I put above is advice from a top doctor (Balistreri) who deals in pediatric liver diseases.
"Through more than 550 publications, Balistreri has helped to clarify the understanding of many aspects of liver diseases in children.
Balistreri has been editor of The Journal of Pediatrics since 1995. He is the former editor-in-chief of the Journal of Pediatric Gastroenterology and Nutrition, and co-editor, associate editor, guest editor, reviewer and member of numerous editorial boards of several journals. He is co-editor of the prestigious text Liver Disease in Children.
In 2000, Balistreri became the first pediatrician to serve as president of the American Association for the Study of Liver Diseases. He has received numerous awards."
and on and on.
https://www.cincinnatichildrens.org/bio/b/william-balistreri
The following is for anyone who happens to read this thread in the future. Note that the first word in Faith's question title is "Why".
The Dr. Balisteri that I wrote about is a top expert in children's liver diseases. The 1st article I cited above, "Lean Patients, Yet Still at Risk for Fatty Liver Disease", by Balisteri is about Faith's condition. The article appears in Medscape which is an 'authoritative source'. That means that it is a top medical site that is taken very seriously by doctors. It's not some random blog.
No current cures are mentioned. As to the "why", since Faith replied that she has no waist fat, we can move to the last thing Balisteri says about possible cause: "In my opinion, the role of other environmental factors, such as early antibiotic exposure and alterations in the microbiome, would be additional fruitful areas of investigation." https://www.medscape.com/viewarticle/868783_2
Very simple and easy to understand, once you know that a simplified definition of microbiome is "gut bacteria".
(The thinking behind that is common knowledge: almost everything that gets absorbed from the intestines initially goes right to the liver. That can include bad substances that come from any bad bacteria in the intestines. Those bad substances can cause inflammation which possibly leads to NAFLD or NASH, without being overweight. Faith had said that she was ill last year. It's not known if she was sick often when younger. If anyone was sick and received antibiotics, that can mess up the normal gut bacteria and leave the way open for bad bacteria.)
The therapy consists of probiotics (good bacteria) and prebiotics (food for good bacteria, so they thrive). There are some other things as well. That therapy seems harmless and fairly easy to do, but anyone should as always ask their doctor if it's okay to try. Your doctor might have considered it and decided against it, so you can ask why.
So there you have it, a very top doctor in NAFLD/NASH in non-obese children wrote his opinion on what might be helpful. It could further be looked into what experiments are currently under way.