March 18, 2026

Looking Beyond the Familiar: Understanding Lesser-Known Intellectual and Developmental Disabilities

Autism Care
Stories
News

Understanding the diversity within I/DD

Conversations about accessibility, inclusion, and neurodiversity are taking place in schools, workplaces, healthcare, and everyday life. As these discussions around disability become increasingly common, many people are left wondering what certain terms mean or what diagnoses involve.

One term that often appears in these conversations is intellectual and developmental disabilities, commonly shortened to I/DD.

Conditions such as Autism Spectrum disorder or Down syndrome have become easily recognizable. These diagnoses are widely discussed and represented in media, education, and advocacy efforts.

The spectrum of intellectual and developmental disabilities is broader than media portrayals, and increased awareness can empower communities to support individuals living with these conditions.

Understanding these lesser-known disabilities is essential for fostering a more inclusive community where diverse experiences are recognized and supported, encouraging the audience to see the relevance of broadening their awareness.

What Are Intellectual and Developmental Disabilities?

Intellectual and developmental disabilities refer to a group of conditions that often begin during childhood and affect aspects of physical, learning, language, or behavioral development.

Developmental disabilities often impact areas such as learning, problem-solving, communication, mobility, or self-care. These conditions typically appear before age 18 and may persist throughout a person's life. Intellectual disabilities refer to measurable differences in cognitive functioning, particularly in reasoning, learning, and decision-making. Other areas of impact include behaviors like communication, social participation, and independent living skills.

Developmental disabilities can also include conditions that primarily affect physical or neurological development, meaning the term I/DD encompasses a wide range of diagnoses and experiences.

In the United States, developmental disabilities are more common than many people realize. Approximately one in six children has been diagnosed with a developmental disability.

Why Some Diagnoses Are More Recognized Than Others

Despite the number of people affected by I/DD, public awareness often centers on a handful of conditions.

There are several reasons why some diagnoses are more widely recognized.

First, some conditions occur more frequently. Diagnoses with larger populations naturally receive more research attention, medical focus, and public conversation.

Screening and diagnostic tools have also drastically improved, enabling earlier detection and intervention, which can significantly influence individuals' development and quality of life, underscoring how increased awareness empowers communities to make a difference.

Finally, advocacy and storytelling play a crucial role in bringing lesser-known conditions into public view, thereby increasing awareness and understanding of the diverse experiences within the disability community.

While this visibility is important, it can lead to overlooking other diagnoses. Many individuals live with rare or lesser-known conditions that still fall under the umbrella of I/DD.

Learning about these conditions helps foster empathy and appreciation for the diversity within the disability community, encouraging the audience to support inclusive environments.

Examples of Lesser-Known Intellectual and Developmental Disabilities

Rett Syndrome

A rare genetic neurological disorder, Rett Syndrome, primarily affects girls.

Children with Rett syndrome often develop typically during the first several months of life. Over time, however, they may begin to lose previously acquired skills such as spoken language or purposeful hand movements.

Stemming from a mutation in the MECP2 gene, which plays an important role in brain development, individuals with Rett syndrome may experience challenges related to communication, mobility, coordination, and seizures.

Although Rett syndrome affects roughly 1 in 10,000 females, many people outside the medical community are unfamiliar with the condition.

Sanfilippo Syndrome

Sanfilippo syndrome, also known as mucopolysaccharidosis type III (MPS III), is a rare genetic metabolic disorder that affects the body's ability to break down certain complex sugars.

Over time, these substances accumulate in the brain and nervous system, leading to progressive developmental delays, behavioral changes, and loss of previously learned skills. Because symptoms often appear in early childhood and can resemble other developmental conditions at first, diagnosis may take time.

Individuals with Sanfilippo syndrome typically require significant medical and supportive care as the condition progresses.

Fragile X Syndrome

Another condition that receives less public attention is Fragile X syndrome. It is the most common inherited cause of intellectual disability.

A mutation in the FMR1 gene on the X chromosome causes fragile X syndrome. Due to genetic origins, parents may pass the condition down to their children.

Individuals with Fragile X syndrome may experience developmental delays, learning differences, and social or behavioral challenges. Some people with Fragile X also show characteristics that overlap with autism spectrum disorder.

According to the CDC, Fragile X syndrome occurs in approximately 1 in 7,000 males and 1 in 11,000 females, making it relatively rare but still an important part of the I/DD landscape.

Williams Syndrome

Williams syndrome is another genetic condition that affects development.

The deletion of a small section of chromosome 7 that causes Williams syndrome occurs in roughly 1 in 7,500 to 18,000 people.

Individuals with Williams syndrome often experience mild to moderate intellectual disability in addition to unique cognitive occurrences. Many have strong verbal abilities and highly social personalities, while experiencing challenges with visual-spatial reasoning or certain types of learning.

Like many developmental disabilities, Williams syndrome highlights how individuals can experience both challenges and distinctive strengths.

More Lesser-Known Intellectual and Developmental Disabilities

While every developmental disability affects individuals differently, many conditions remain relatively unfamiliar outside of medical or advocacy communities. Below are a few additional examples that illustrate the diversity within the I/DD community.

Angelman Syndrome

Angelman syndrome is a rare genetic condition that affects the nervous system and causes developmental delays, limited speech, and challenges with balance and movement. Individuals with Angelman syndrome often communicate through gestures, assistive technology, or other nonverbal methods.

Prader–Willi Syndrome

Prader–Willi syndrome is a genetic condition that affects growth, metabolism, and development. Many individuals experience low muscle tone early in life and later develop a strong appetite due to differences in how the brain regulates hunger.

Phelan-McDermid Syndrome

Phelan-McDermid syndrome stems from a deletion on chromosome 22 and may lead to developmental delays, intellectual disability, and speech differences. Some individuals also show characteristics associated with autism.

Smith-Magenis Syndrome

Smith-Magenis syndrome is a developmental disorder caused by a genetic change on chromosome 17. Individuals may experience intellectual disability, sleep disturbances, and behavioral differences.

Cri-du-chat Syndrome

A deletion on chromosome 5 causes Cri-du-chat syndrome. Named after the distinctive cry some infants make, the condition can resemble a cat's cry.

Kabuki Syndrome

Kabuki syndrome is a rare genetic condition that can affect growth, learning, and development, often accompanied by mild to moderate intellectual disability.

Additional Conditions Often Seen in Developmental Disability Services

Other conditions within developmental disability support systems lack awareness, including:

Fetal Alcohol Spectrum Disorders (FASD)

Fetal Alcohol Spectrum Disorders describe a group of conditions that can occur when the parent exposes their developing baby to alcohol during pregnancy. Individuals may experience learning disabilities, attention differences, and challenges with memory or impulse control.

Tuberous Sclerosis Complex

Tuberous sclerosis complex is a genetic condition that causes benign tumors to grow in different organs, including the brain. Many individuals experience seizures or developmental delays.

CDKL5 Deficiency Disorder

CDKL5 deficiency disorder is a rare neurological condition that often begins in early infancy and involves severe seizures along with developmental delays.

Landau-Kleffner Syndrome

Landau-Kleffner syndrome is a rare childhood neurological disorder that affects a child's ability to understand and use language. Children may develop speech typically at first, only to gradually lose language skills.

While many of these diagnoses are rare, they highlight the incredible diversity within the intellectual and developmental disability community.

Why Awareness Matters

For individuals and families navigating a rare diagnosis, awareness can make all the difference.

Lesser-known conditions may be harder to identify, delaying diagnosis and access to services. Families may also struggle to find resources, support networks, or community connections.

Research suggests that early intervention and supportive services, including therapies, educational supports, and community programs, can help individuals with developmental disabilities build skills and independence over time.

Increasing awareness helps ensure that people with all types of disabilities, not just the most familiar ones, have access to the understanding and support they deserve.

Advocacy in Action: Turning Awareness into Impact

Understanding intellectual and developmental disabilities is an important step in building a more inclusive world; however, awareness alone isn't enough. Behind many of the services, supports, and opportunities available to individuals with I/DD is ongoing advocacy work that helps shape the systems people rely on every day.

At I Am Boundless, advocacy is a key part of our work. In addition to providing care and support, Boundless actively engages in policy and systems-level conversations at both the state and federal levels. By partnering with organizations such as the Ohio Council and the Ohio Children's Alliance, these efforts help ensure that the needs of individuals with developmental disabilities and their families are represented in decisions that affect care, funding, and access to services.

A major focus of this work is supporting programs serving children and youth, including OhioRISE. This statewide initiative provides coordinated care for young people with complex behavioral health needs. As one of the care management entities helping implement OhioRISE, Boundless brings real-world experience into conversations about how the program can continue to grow and improve.

Advocacy also means looking ahead. Policy decisions don't happen in isolation—they are shaped by elected officials, budgets, and broader systems like Medicaid, which plays a significant role in funding services for individuals with I/DD. Because of this, maintaining strong relationships with policymakers and staying engaged in the legislative process is essential to ensuring that services remain accessible and responsive to community needs.

For those who want to be part of that impact, there are ways to get involved. Boundless Advocates, the organization's grassroots advocacy group, offers opportunities for individuals to stay informed, participate in events, and engage in meaningful conversations about policy and change. As the policy landscape continues to evolve, especially during election years, staying informed and engaged can make a meaningful difference.

As conversations around disability continue to grow, advocacy ensures those conversations lead to action. By staying engaged and informed, communities can help shape a future where all individuals, regardless of diagnosis, have access to the support and opportunities they deserve.

Supporting the Full Spectrum of Human Potential

At I Am Boundless, the focus extends beyond a diagnosis.

Every person deserves opportunities to learn, connect, and live a meaningful life, regardless of whether their disability is widely recognized or rarely discussed.

Through whole-person, whole-life care, I Am Boundless works to meet people where they are and support them wherever their path may lead.

The diversity within the intellectual and developmental disability community reminds us that there is no single story or experience. Each person brings their own strengths, challenges, and potential.

By continuing to learn about the full range of developmental disabilities, communities can become more compassionate, inclusive, and supportive places for everyone.

Now is the time to turn awareness into action. Stay informed about the issues that impact individuals with I/DD, engage with advocacy efforts like Boundless Advocates, and make your voice heard—especially during key moments like elections and policy changes. The systems that shape care and opportunity depend on people who are willing to show up, speak out, and stay involved.

To get involved with Boundless Advocates, contact

Anthony Kukura at akukura@iamboundless.org

Resources

https://www.cdc.gov/ncbddd/developmentaldisabilities/data.html

https://www.cdc.gov/fasd/about/index.html

https://www.cdc.gov/fragile-x-syndrome/about/index.html

https://www.nichd.nih.gov/health/topics/idds/conditioninfo

https://www.ninds.nih.gov/health-information/disorders/tuberous-sclerosis

https://www.ninds.nih.gov/health-information/disorders/cdkl5-deficiency-disorder

https://www.mayoclinic.org/diseases-conditions/rett-syndrome/symptoms-causes/syc-20377227

https://medlineplus.gov/genetics/condition/angelman-syndrome/

https://medlineplus.gov/genetics/condition/prader-willi-syndrome/