Hope for FBXL4

A significant number of FBXL4 children pass away before 2 years old, with a handful of cases living into their 30s and 40s. Because FBXL4 is still a newly discovered diagnosis, we expect significant bias that reported cases are on the more severe end of the spectrum and that more minor cases will be discovered soon. For example, as of 2025, there is a confirmed 22-year-old and an unrelated 44-year old, both of whom, despite some mental delays and medical concerns, are able to walk and talk so can be assumed to have a less impactful mutation than other reported cases.

While formal literature reports ~100 cases, we are aware of ~240 cases and expect closer to 300-400 total diagnosed children, with the number increasing each year as genetic testing becomes more widely available worldwide. More information is also needed to understand the correlation of the quality of local medical care to life expectancy. For example, Children’s Hospital of Orange County (California) has multiple patients in their teens and has not yet lost a child to FBXL4.

A project is ongoing to create a registry of FBXL4 cases - Contact HopeForFBXL4@gmail.com to learn more.

Every child is unique (see FAQ explanation below). The majority of children cannot walk or talk, but there are exceptions. Generally the brain is most affected and so children generally do not progress past the cognitive capability of a 2-year old, with many remaining much younger. Similarly, motor planning and muscle tone are severely impacted. Many children are unable to hold up their head and can only utilize their arms and legs in limited motion. Other children play with toys and scoot around the room, similar to a young toddler. Many children are unable to feed by mouth and are fed via feeding tubes, but there are also affected children who do not have a feeding tube.

While all FBXL4 children share the same "primary issue" which is mitochondrial disease, all affected abilities and health conditions are secondary impacts and vary specific to the child. This page coming soon will provide a more examples of the conditions which may develop in some children.

While the FBXL4 diagnosis may only have ~100 cases in literature from the last 12 years, the FBXL4 gene and general mitochondrial function is critical for every cell in everyone’s body. Despite being a basic foundation of life, we understand very little about mitochondria and there is an entire frontier of research related to mitochondria which will lead to treatments for many, many conditions beyond mitochondrial disease.

For example, mitochondrial dysfunction is a key factor in Alzheimer's disease and is recently theorized to be a primary cause of the disease. Abnormal mitochondria are also involved in a wide range of more common health issues, such as Type 2 diabetes, Parkinson’s Disease, Epilepsy, and even human aging. Outside the healthcare industry, the multi-billion dollar beauty industry is also in search for ways to reduce the signs of aging. A treatment that improves mitochondrial function to support these more common conditions could also be a gateway to a treatment for FBXL4 (or vice versa).

There is even groundbreaking scientific interest that altering mitochondrial function may offer a treatment for cancer. Apart from solely being “the powerhouse of the cell”, mitochondria have recently been recognized for additional functions. For example, Mitochondria have recently been found to also be involved in apoptosis, the process of programmed cell death which is critical to retiring old or damaged cells. Too little apoptosis can lead to cancer, which is when bad cells are not being destroyed. Further, Mitochondria has also been only recently recognized to provide a role as cell "organizer" in dictating which cells turn into which body part. There is an emerging theory that cancer cells may take advantage of this process to activate their continued growth. Read this article from Yale Medicine to learn more. 

Per the Children's Hospital of Philadelphia, Mitochondrial diseases at-large affect at least 1 in every 4,300 people globally. Every 30 minutes, a child is born who will develop a mitochondrial disorder or disease by age 10. Even these figures are expected to be underestimations. Most likely, there are many undiagnosed cases of mitochondrial diseases for those with less severe symptoms or those in countries with less access to genetic testing and advanced medical care.

Mitochondrial Disease is about as prevalent as childhood cancer. While there is still no cure for cancer, there is substantially more research and treatment, likely because cancer also affects adults who are funding and advocating for a cure. Mitochondrial disease is generally present at birth and a large percentage of affected individuals do not survive childhood. Unlike cancer, where you may know an individual before their diagnosis, the medically-fragile nature of mitochondrial disease makes it so that affected children are not commonly out in public. Even within mitochondrial disease, there are thousands of specific diagnoses, each of which are individually rare and unique, making it harder yet to research a cure, let alone recognize the name of the condition.

More than anything, we need a cure for these children.

Selection in-process to identify key research Initiatives to support financially (CHOC fundraiser and project largely completed)

There are also many other ways to support families affected by FBXL4. With a life-limiting, progressive disease, the emotional load on parents is immense and all-consuming. Families with FBXL4 children are pouring their hearts, souls, and bodies into those children and both tangible (e.g. meal trains) and intangible (e.g. emotional encouragement) support can be invaluable. 

Recognize also that FBXL4 children are extremely immunocompromised, equivalent to a cancer patient undergoing chemotherapy. Children with this condition have died from the common cold. If you are seeing these children in-person, please take all precautions to prevent spread of infection and, in general, be mindful that these families have very limited capability to leave their homes.

There are many other ways to support families affected by FBXL4. Coming soon -  Tips to support affected families.

Today, there is no cure for any form of Mitochondrial Disease. For all Mitochondrial Diseases, including FBXL4, the best course of action is to offer vitamins and supplements to optimize mitochondrial efficiency and then treat secondary symptoms as they arise.

A collection of vitamins and supplements is commonly mixed together into what some call a “Mito Cocktail”. These supplements are effectively a “Hail Mary” attempt to maximize the function of the limited mitochondria that these children have. Effectivity is difficult to quantify, but is not expected to make a major impact on the child’s prognosis. Depending on the mutation, many FBXL4 children have between 50-80% of the mitochondria of a healthy human, so if we can increase the efficiency of the mitochondria they do have even 5%, every little bit counts. A supplement such as this could be the difference in if a child ever walks so should not be discredited, but also, this supplement is not going to completely “cure” the child.

More than anything, we “hope for the best” with these children and, as physical conditions arise, we treat those symptoms directly. For example, if the heart or brain is maldeveloped, surgeries can help maintain flow and function. Since the children often have poor oral-motor skills to feed, G-tube feeding can greatly increase nutritional intake. Various physical therapy techniques and orthopedic surgeries can assist these children in deficiencies related to low muscle tone and compromised skeletal development.

Emery specifically is on an experimental ketogenic diet. This is a very novel potential treatment for Mitochondrial Diseases and has only been attempted in 2 other children with FBXL4. Theory for why the keto diet may be beneficial will be added to Introduction to Mitochondrial Systems (coming soon).

Coming Soon: List of commonly considered Mitochondrial Disease drugs and their association with FBXL4

Plan A - Correct the Gene

The only true “cure” for a genetic condition would be gene therapy. This would entail modifying DNA in every cell of their bodies to no longer have this mutation. While genetic therapy has proven successful in correcting some mutations, this technology is still in infancy. Current technologies can target selected cells or tissues to achieve a therapeutic effect, but we do not yet have the capability to treat every cell in the body. The field of genetics is a new frontier and we are likely on the precipice of significant discovery. 

Read a publication summarizing current gene therapy limitations specific to mitochondrial disease. 

Plan B - Reduce the Mitophagy (destruction of mitochondria)

This is the best path forward right now with the technology we have and there are a few potential approaches. Because BNIP3 and NIX join together to cause this mitophagy, you could reduce either, both, or impede the way that the two attach to one another.

Because there are many applications outside FBXL4, most notably Parkinson's which is roughly an inverse disease to FBXL4, multiple labs around the world are working on this. Our tiny disease community yet multiple researchers dedicated to solving it! Many researchers confided their proprietary work with me, so I cannot yet share until they are ready to publish (or seek human experimentation), but please rest assured that a LOT of progress is ongoing.

1. Drug repurposing - Multiple teams are scanning a number of existing drugs to see if anything already available will do what we're looking for. Multiple labs will be publishing some results later in 2025. Even sharing which drugs didn't work which will help other labs solve FBXL4. This Australian Postdoc is just one of many labs working in this space

2. Develop an FBXL4-specific drug - Drug development takes time and so it will be at least 1-2 years before we can see these results. If we are unable to repurpose an existing drug, there is significant promise that a drug specifically targeting BNIP3/NIX proteins can be made and will rescue these children. We know this because at least one lab has FULLY RESCUED FBXL4-affected mice by reducing BNIP3 and NIX. Granted, any existing tissue damage persists (i.e. we do not yet have a way to regrow brain cells or fix organ damage), but the cells returned to a healthy state moving forward. Imagine a life moving forward without Mito crashes!

Plan C: Give Cells More Mitochondria

There may be two ways to do this.

1. Increase mitochondrial biogenesis (creation) to counteract the destruction. This means the cell itself would need signaled to make more of its own mitochondria. Since these children are already doing an insane amount of biogenesis, we likely cannot reasonably encourage much more.

2. Insert more mitochondria into the cell - Recently proven possible via mitochondrial transplantation. This is a VERY new field with many open obstacles like how to deliver across the blood-brain barrier. Also, because FBXL4 is a nuclear gene, our children would continue to destroy the new mitochondria so they would require very frequent infusions (perhaps by IV) to "top up" their total mitochondria. There is some promise from mice data from another form of Mitochondrial Disease.

Plan D: Make the mitochondria they do have more efficient

Depending on the severity of mutation, some FBXL4 children have about 60% total mitochondria of a healthy children. Its asking a lot to output the same energy with only 60%, so while getting the most energy we can out of what they do have will not be a "cure", every bit counts. Effectively, all the various mito cocktail supplements are trying to do this.

Plan E: Treat the symptoms

This is what we mostly do today. If a child develops heart conditions, initiate drugs or surgeries. Same for any other organ or system which begins to fail. It is a very reactive approach and is not saving our children.

FBXL4 children are medically fragile and their families live in constant anxiety that health may change on a dime. FBXL4 reduces the quantity of mitochondria in the cells which gives these children two battles: not enough energy to develop properly and acid build up poisoning their systems. Generally, improper development is a gradual process which provides signs of declining function vs an immediate loss of function (i.e. we may notice the brain growing at a slower rate, the heart starting to get stiffer, etc.) The acid buildup in their systems, however, can change abruptly and have devastating consequences.

For reasons we do not always understand, any form of metabolic stress (such as an infection, diet change, medication change, environmental factors, growth spurt, etc.) can unsettle the very fine line of metabolic function these children have. Because their metabolisms are so fragile, the smallest shift can effectively “clog” the processing of food creating an immediate build-up of acid that can cause severe damage to any organ. Periods of extreme acidosis can onset as quickly as a few hours. Because their bodies are already weak, they are usually unable to self-recover when their bodies effectively spiral (more acid, less function, less function, more acid). Even with medical intervention, it's not always a guarantee that correction can be made. Depending on the extent of acidosis and the duration of the episode, significant organ damage across the body can be permanent or temporary.

Case Study Example: Say a child gets the common cold. In effort to conserve energy, most of these children do not regularly keep white blood cells staffed up to fight infection. When they do catch an infection, their bodies must ramp up a response. During this ramp process, their metabolism becomes dysregulated and the acid builds up even more than usual, spiking to acute quantities that can poison organs quickly. Their breathing increases to compensate for the acid and then, between the rapid breathing and the acidic environment, their lungs begin to fail and they enter respiratory distress. If access to advanced medical care is present, intubation may sustain the lungs while bicarbonate IV drips may counterbalance the acid until their systems can re-regulate. A metabolic episode like this could initiate many different subsequent medical conditions, all of which may involve a “well child” transitioning to “near death” in as little as a few hours.

Human development explodes during baby-hood. Babies are little engines and our metabolisms are faster as a baby than any other life stage. Most babies have tripled their birth weight in the first year. Not only do babies explode in physical size, but their nervous system is exploding with energy-intensive development. For children who already exist on a fine line of energy to support their current needs, living in a life stage with such explosive growth stresses their system. Also, the fact that their body is changing daily means their metabolism must continually adjust which opens the door to metabolic distress if their metabolism doesn’t adapt in sync with their bodily  needs.

After babyhood, these children may experience some varying amount of time with increased stability but eventually become progressively “unstable” yet again as they age due to an accumulation of ailments throughout their life. See next FAQ.

FBXL4 is a “progressive disease” and one that can affect any system in the body. Every day without a cure leaves these children with additional permanent damage.  For the children who are “fortunate” enough to evade a lethal acute acidotic event (sometimes caused by unexplained reasons - See above FAQ), their disease will still progress with age.  Due to an accumulation of under-development and/or an accumulation of injury from acidosis throughout their life, eventually enough systems are compromised enough that substantial medical intervention is required and, assuming those interventions are even possible, families may be faced with unimaginable decisions.

Each child is unique (see next FAQ) and so “disease progression” looks different from child to child. For example, some children develop “hypertrophic cardiomyopathy” which causes the heart muscle to thicken, making it progressively harder for the heart to pump. Separately, some children accumulate brain injury and regress developmental milestones until eventually the portion of their brain that controls vital bodily functions (i.e. breathing) is damaged. Such brain injuries may or may not involve progressively frequent seizures.  For any number of reasons, some GI tracts have a progressively harder time digesting food, or throats have a progressively harder time clearing their airway, or immune systems may have a progressively harder time ramping up to fight infections.

Coming soon: Additional examples of "common" symptoms that may develop over time in some children.

One analogy is that a team can still win a football game with a weak quarterback if the remainder of the offensive and defensive team is strong. Similarly, FBXL4 is just one gene among tens of thousands in the body. 

• FBXL4 children who are genetically more disposed to heart issues are more likely to develop heart issues than other FBXL4 children.

• Even metabolically, there are hundreds of genes which impact mitochondrial function, so some FBXL4 children have a more energy-efficient metabolism than others due to mitochondrial genes outside of FBXL4.

• Specific acidotic events in a child’s life can cause catastrophic damage. When these children are sick with an infection or another destabilizing event, their acidity can skyrocket and damage organs, sometimes without repair. It’s a matter of chance where the child is in stage of development at time of event, the severity of the event, and their other overall genetics which organs are affected and in what way.

• Even within a diagnosis of FBXL4, there are many different mutations a child may receive. Each specific mutation causes its own impact to the level of function of FBXL4 processes. Some mutations cause more severe mitochondria impact than other mutations. 

• Note – For above reasons, there are many siblings who share FBXL4 diagnosis with the exact same FBXL4 genetic mutation, but have vastly differing medical conditions and developmental abilities.

All of these variations accumulate over the child’s life and impact the child’s specific capabilities. Due to the number of factors, it is impossible to predict the outcome of any one child.

FBXL4 is just one of over 100 genes which have been identified so far to cause Leigh Syndrome (aka Leigh’s Disease, or subacute necrotizing encephalomyelopathy). Mitochondrial Disease is an umbrella term for conditions which impact mitochondrial health. Under that, Leigh Syndrome is an umbrella term for a form of Mitochondrial Disease involving significant nervous system abnormalities, commonly diagnosed via Brain MRI findings. Leigh Syndrome is one of the more common varieties of Mitochondrial Disease and affects an estimated 1 in 40,000 individuals.

The diagnosis of Leigh Syndrome is largely outdated and only used today for primary diagnosis in children who do not match with a known genetic mutation. Prior to scientific advancements to identify the exact genetic mutation, doctors would group children with similar symptoms into syndromes. Today, we know that many genetic mutations may present similar symptoms, but that each gene has unique characteristics. Rather than treating patients via common symptoms, we can now treat based on the underlying cause and focus research on the exact mechanisms of the affected gene.

FBXL4 children appear with symptoms similar to other children with Leigh Syndrome, but the actual mechanisms for their diseases vary. Think of it like a different flavor of the same food. Other Leigh Syndrome children can provide some information on the kinds of secondary issues which often occur from mitochondrial dysfunction, but a treatment which helps one Leigh child may not necessarily help someone with FBXL4 since the root cause is different. In today’s world with limited data on FBXL4 specifically, data from other Leigh Syndrome individuals is the next best source of data, though should be processed with a grain-of-salt that individuals in that group have different underlying diseases.

Mitochondrial Diseases classification chart here.

Learn more about Leigh Syndrome here

Some forms of Mitochondrial Disease are passed via mitochondrial DNA (mtDNA), which exists within the mitochondria of the cell and is passed only from the mother. FBXL4 is instead a Nuclear DNA gene. Nuclear DNA exists within the nucleus of the cell and requires a copy from both parents.

There is growing evidence that "carriers" of FBXL4, meaning people who have 1 healthy copy and 1 mutated copy, may still have some symptoms. Those who are FBXL4 carriers who have otherwise compromised mitochondrial health are more likely to show symptoms.

Some prenatal genetic test panels are starting to include the FBXL4 gene and some fetuses have been diagnosed prenatally starting in 2024. That said, this gene is too rare to be included in most prenatal DNA test routines. For this reason, many fetuses are still undiagnosed. 

While not specific enough to diagnose FBXL4, there are early markers present since the disease begins during fetal development. For example, the brain cerebellum is already underdeveloped (smaller) in-utero. While this can be difficult to see in fetal ultrasounds or MRI, the increased cerebral fluid surrounding the region has been noticed via routine fetal ultrasound for some FBXL4 children. This marker is called “enlarged cisterna magna” (or “mega cisterna magna”). This marker can be indicative of many conditions, most notably an arachnoid cyst, but also many genetic conditions, most commonly Dandy-Walker Syndrome. There are also cases of children with this "cisterna magna" marker on fetal MRI who have no health impact. In Emery’s case, subsequent fetal MRI and significant  fetal genetic testing did not yield definitive diagnosis and the condition was misdiagnosed as “normal variant”, leading us to believe she would be a healthy baby.

IVF technology enables embryos to be screened for this mutation. Similar to fetal testing, this gene is so rare that most genetic panels do not include FBXL4 in their tests, but if a couple has probable reason (such as family history or prior affected child) the embryos can be tested via PGT-M technology.

Disease: “An abnormal condition that affects the structure or function of part or all of the body and is usually associated with specific signs and symptoms.” 

Most people immediately think of “infection” when they think disease. However, most diseases are not infectious. Such diseases are commonly referred to as “non-communicable diseases” (NCD). NCDs are a group of conditions that are not caused by an acute infection and result in long-term health consequences. Heart disease, stroke, cancer, diabetes and chronic lung disease, are the five most prevalent NCDs and collectively are responsible for 74% of all deaths worldwide (per WHO website). 

To help conceptualize: most people recognize cancer as a disease. Cancer cells accumulate as a person ages, leading to a higher risk of developing cancer later in life, though childhood cancer can also occur. Mitochondrial disease also affects cells, but generally every cell in the body and from the start of life.

The human body is resilient and filled with many “fail-safes” enabling our bodies to adapt to a large number of deficiencies. Sometimes these "deficiencies" make us unique and create the spectrum of humanity. Children with Mitochondrial Disease are proof that we do not need perfect mitochondrial function to survive. While FBXL4 children have significant disabilities, their bodies do have enough energy for some amount of bodily development. The exact minimum viable value is unknown. FBXL4 children are miracles from the day they are born.

While it appears the mother’s body supplements fetal development, metabolic deficiencies do begin in the womb. It is unclear how many babies are lost to miscarriage due to this condition.

Because the age, abilities, and medical complications of these children vary so significantly, life can look very different from child to child.

Meet Emery

(More spotlight children to be added in the future.)