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Invisible and Visible Limb Differences in Children

As humans, we’re all unique. Sometimes, those differences are more noticeable to the outside world. A limb difference is having an arm or leg that’s different on one side than the other, or having a limb, such as a finger, that looks different from others. Sometimes, these differences can change the course of a child’s life, while others are less noticeable, or even “invisible” to an onlooker, and can have multiple treatment options. No matter the limb difference, children can be incredibly adaptable and can learn to live well with their limitations, given the right support.

Types of Limb Differences

Limb differences vary from extremely minor to severe and disabling. On the mild end, about half the population is thought to have some kind of difference in leg length, usually barely perceptible. Clinodactyly, when the pinkie finger is slightly curved, is inherited and thought to affect about 1 in 5 babies.

Among the more noticeable but mild limb differences, the most common is polydactyly—when a baby is born with one or more extra fingers. The condition tends to run in families, affecting roughly 1 in every 500 to 1,000 babies. About 1 in every 2,000 babies have syndactyly, which is when two or more fingers don’t separate. Clubfoot is perhaps the most well-known lower limb difference, found in roughly 1 to 2 in every 1,000 newborns. All of these conditions can be managed with surgery and other therapies.

A more significant limb difference occurs when one limb is significantly larger or smaller than the other. When a child is missing part of, or an entire, arm or leg at birth, it’s known as a limb reduction. Limb reductions are relatively rare, occurring in about 1 in 1,900 babies.

Image of Hutt Martin in an incubator at the hospital
Credit: Lindi Martin | Hutt Martin

At Lindi Martin’s 11-week prenatal appointment, doctors couldn’t detect upper limbs and suspected Hutt, her baby, wouldn’t survive much past birth. An amniocentesis (a prenatal genetic test using amniotic fluid) diagnosed him with thrombocytopenia, absent radius syndrome (TAR). TAR is a very rare genetic disease that affects fewer than 1 in 100,000 newborns. It’s caused by two recessive gene mutations, meaning a child is affected only if they inherit the gene mutations from both parents.

In kids with TAR, the bone marrow doesn’t make platelets. Blood doesn’t clot, causing mild to severe hemorrhaging episodes. Hutt, born in August 2022, has a normal life expectancy but will require lifelong platelet transfusions. While this is his most serious complication, it isn’t the most obvious. Kids with TAR are missing their radius, the bone between the elbow and wrist. Hutt has an extra rare case: he is missing all of the bones between his shoulders and wrists, and his hands begin at his shoulders.

What Causes Limb Differences?

Congenital limb differences are thought to occur when a baby’s blood vessel system doesn’t mature at the typical rate during pregnancy, so some tissues don’t get the blood flow they need to develop, explains Hutt’s doctor Laurel Benson, M.D., a pediatric orthopedic surgeon in Denver, CO. In many cases, doctors aren’t able to pinpoint the cause. Researchers believe limb differences may be linked to exposure to chemicals, medications, viruses, or tobacco during pregnancy. Otherwise, “we think that just about all of the causes are in some way genetic,” says Karamitopoulos.

Some mild genetic limb differences, such as polydactyly and clubfoot, tend to run in families. But more often, limb differences are caused by random gene mutations that aren’t passed down by parents. As our ability to map out our genes improves, so have diagnoses. While there’s still a lot we don’t know, “we’re learning more and more about some limb differences that we hadn’t been able to really classify before,” says Benson.

Diagnosing Limb Differences

Limb reductions are usually picked up during routine prenatal scans, says Karamitopoulos.

Image of Angelo Cohen
Credit: Jenna Cohen | Angelo Cohen

At Jenna Cohen’s routine 20-week ultrasound, doctors discovered that her baby was missing his fibula, the smaller of the two bones in the lower leg. Her son, Angelo, born in April 2020, has fibular hemimelia, a condition that affects between 1 in 50,000 and 1 in 135,000 newborns. The condition is caused by rare genetic changes that occur randomly. Doctors estimated that without treatment, Angelo’s affected leg would end up being 6 inches shorter than his other leg.

If a limb difference is suspected after birth, doctors will perform a physical exam and may order imaging to check for bone issues. Sometimes, it’s the parents who notice a difference. “Parents know their kids best,” says Karamitopoulos. “It’s really important to bring it up to the pediatrician as soon as possible.”

Depending on the severity of the abnormality, genetic testing for your child may be recommended, says Karamitopoulos. “In some cases, the limb difference is the obvious thing, but it’s not the most dangerous thing,” she explains. For example, abnormalities on the thumb side of the hand may signal one of several genetic conditions, such as Fanconi anemia. This very rare condition impacts the bone marrow and can be fatal without a bone marrow transplant.

Families sometimes hesitate to get genetic testing even after a baby is born, says Karamitopoulos, but results may lead to a diagnosis with treatment options. “Sometimes we find that this is just isolated and random,” she says. “But it’s always good to know…because many of these issues are treatable.”

Treatments for Limb Differences

Therapies for limb differences vary widely, depending on the severity. “We do have pretty powerful technologies,” says Karamitopoulos.

If your child has a limb difference, an orthopedic surgeon can help you understand the scale of your child’s condition and treatment options. Cohen suggests getting multiple opinions and asking doctors about their success rates, their vision for your child, and their timeline.

Some therapies are curative. Clubfoot treatment, for example, involves casting, physical therapy soon after birth, and sometimes surgery. “Then they’re up and walking as typical 1-year-olds,” says Benson, who notes that sports stars Troy Aikman and Kristi Yamaguchi had clubfoot at birth.

For limbs that can be reconstructed, surgery and skin grafts may improve alignment and appearance. An extra finger or toe can be removed with a small surgery. More complex conditions may involve multiple surgeries over a child’s lifetime.

Image of Angelo Cohen
Credit: Jenna Cohen | Angelo Cohen

If limbs are a different length, it can be possible to slow down the growth of a longer limb or gradually lengthen a shorter one. Angelo had surgeries at 21 and 22 months old to realign his foot and attach a metal apparatus to the outside of his leg, which gradually lengthened his tibia bone. He’ll have to repeat the lengthening process two more times, at 5 years old and several years later when his lower body stops growing. Coupled with physical therapy (PT), this will help his shorter leg function normally. PT can help strengthen muscles and improve range of motion. “He has no limitations,” says Cohen. “He can live a normal life.”

Hutt began PT when he was 1 day old. He is currently working on exercises to strengthen his lower body to prepare for walking. Occupational therapy (OT) teaches skills to achieve everyday tasks. Thanks to twice-weekly OT sessions (and lots of practice at home), Hutt learned to roll over, sit up by himself, and grab objects by 18 months old—all without arms. Because he can’t crawl, he scoots. “He’s got his own journey. He’s going to have to figure it out. But he’s going to be able to do everything we can,” says Martin.

For kids with more severe limb differences, specialized assistive or adaptive devices can help them live more independently and make activities easier. Some tools help kids pursue passions—for example, a prosthetic hand for playing golf, baking, or riding a bike.

Benson notes that many children don’t like wearing a prosthetic to replace a missing limb because they can feel hot and heavy. “As soon as they have a choice, they take it off and play without it,” she says. She advises parents to think of using adaptive devices like playing an instrument: If your child is interested, they won’t mind practicing—but don’t pressure them.

Talking about Limb Differences

Research suggests that for kids with limb differences, self-esteem, and mental health depend strongly on how they’re viewed in their family. “The most important thing is to treat kids like kids, no matter what else is going on,” Karamitopoulos says. “Like, yep, you gotta brush your teeth. You gotta do your laundry. You gotta do your homework. You gotta go to school.”

Benson recommends figuring out how you’d like to talk about your child’s condition with others because people will stare and ask questions. She recommends saying something like, “I see you noticed her hand. Yeah, she was born like that, and we know it’s going to make some things different and difficult. But you should see her [hold a bottle, play with toys, etc.]. She’s going to figure it out. She’s amazing.” Knowing what you’re going to say can flip a frustrating scenario. “At the end, it’s all about how wonderful this baby is,” she says.

By listening to what you say, your kids will also learn how to talk about themselves. Benson recalls how one parent talked to her son, Jimmy, who is missing a hand, about how good he is at fixing things and solving problems. “His best friend’s mom told her that her son’s father couldn’t figure out how to hook up their new DVD player. And her son said, ‘Hey, we should call Jimmy. He’s really good at figuring stuff out.’”

Try to let the judgments go. “You know your child. You know what they’re capable of. Yes, they look different, but you want them to grow up and be confident,” Martin says. “Having a limb difference does not define you. You can do what you want to do. You just have to do it a little differently.”

Where Can I Get Support for My Family and My Child?

Martin and Cohen say that private health insurance and Medicaid have covered their children’s medical expenses, but not every state has the same resources. If you’re uninsured or otherwise have to pay out of pocket, Cohen recommends talking to your provider. The Paley Institute, where Angelo is a patient, has a foundation that supports families who need financial assistance.

Also, check out the Steps Charity Worldwide if your child has a lower-limb difference and the Lucky Fin Project for upper-limb differences.

Although having a child with a limb difference can feel isolating, you’re not alone. Facebook groups, nonprofit groups like Team UnLimbited, and hospital support groups offer information and networking with parents managing similar conditions. “Take it with a little bit of a grain of salt, because two kids with the same condition can have wildly different presentations,” says Karamitopoulos. Lean on people you trust for support, including family, healthcare providers, caregivers and teachers, and national and community organizations. “All of those people become part of your team and cheer squad,” Karamitopoulos adds.

Image of Hutt Martin
Credit: Lindi Martin | Hutt Martin

As with any physical disability, life has more challenges. Baby Hutt took things in stride, but things are trickier now that he’s a toddler. “There are days where it’s so frustrating,” says Martin. “Then you see him do something or learn something, like starting to scoot for the first time. It just puts a lot of things in perspective. You’re so excited. It’s just he’s worked so hard for this.”

Remember to focus on your child’s strengths. “These kids restore your faith in the world. They are kind children. They stick up for other kids, and they’re willing to accept differences in others,” says Benson. “They are remarkably well-adjusted. They thrive if you just give them the words for what’s going on.”


References and Further Reading

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