BORN WITH ONE LEG MUCH BIGGER THAN THE OTHER, CASSIE’S RARE CONDITION LEFT HER FAMILY SEARCHING FOR ANSWERS

A Difference Doctors Noticed Before Birth

Before Cassie Chow was born, pregnancy scans had already revealed something unusual: her left leg was much larger than her right.

After her birth in Singapore, Cassie was taken to the neonatal intensive care unit for observation because of the difference in the size of her legs. Although her vital signs and organs were reported to be in order, she also had large, reddish-purple birthmarks across her body.

Her parents, Lynnette Tay and Kenneth Chow, knew that their daughter needed answers. But in those early days, doctors were unable to identify the condition with certainty.

When Cassie was around two weeks old, she underwent an MRI. Even with further investigations, the medical team still could not immediately establish a definitive diagnosis.

A Diagnosis That Took Until Her First Birthday

Cassie was eventually referred to a specialist at KK Women’s and Children’s Hospital. Her family continued seeking information while doctors investigated the unusual growth affecting her leg and the marks on her skin.

It was not until Cassie turned one in 2021 that she received an official diagnosis of PIK3CA-Related Overgrowth Spectrum, commonly known as PROS. Biopsies were performed to help confirm the condition.

PROS is a group of rare disorders associated with changes in the PIK3CA gene. These changes can cause certain tissues to grow excessively or develop abnormally. Depending on the individual, the condition may affect blood vessels, lymph vessels, skin, muscle, soft tissue or bone.

For Cassie, the effects were visible from birth. Her enlarged left leg and widespread birthmarks were important clues, but understanding what they meant required time, specialist assessments and further testing.

When Growing Up Came With Extra Challenges

As Cassie began crawling, the affected leg became more swollen and painful. At around 10 months old, she was photographed wearing a compression bandage intended to help manage the swelling and discomfort.

Her condition required care beyond a single appointment. Her parents had to learn about a rare disorder that many people had never heard of, while navigating a range of medical consultations and treatment decisions.

According to her specialist, PROS can sometimes lead to complications such as pain, infections, reduced function and abnormal blood clotting. The specific effects vary from person to person, which makes continued monitoring important.

Cassie’s care has included medication and regular medical follow-up. Her family has worked closely with specialists to monitor her health and manage the condition as she grows.

A Family Determined to Understand the Condition

Lynnette and Kenneth did not stop looking for information after receiving the diagnosis. They read medical journals, joined rare-disease support groups and attended conferences to better understand the different ways PROS can affect children.

At one point, the family was seeing seven different medical specialists within a two-month period. The parents had to become advocates for their daughter while learning how to coordinate the many parts of her care.

They also took practical steps to help others understand Cassie’s needs. When she started preschool, Lynnette prepared a guide with photographs and factual information about her condition so teachers could better support her in everyday situations.

The family hopes Cassie will be able to participate in activities and enjoy childhood without being unnecessarily restricted by her diagnosis. At the same time, they know that some situations may require planning, awareness and additional support.

More Than a Rare Diagnosis

By the time she was five, Cassie was described as a bright and joyful little girl who enjoyed simple pleasures and had the support of a family determined to help her thrive.

Her story highlights the challenges of living with a rare condition that can affect a child’s body in visible ways. It also shows how difficult it can be for families to find answers when a disorder is unfamiliar and its effects vary from one patient to another.

Cassie’s journey is ongoing, and her medical needs will continue to be monitored. Her parents’ hope is that she can grow up with the freedom to explore the world, build relationships and enjoy the same everyday experiences as other children—with appropriate support whenever she needs it.

Source: The Straits Times, “Her left leg is much bigger than her right due to a gene mutation,” April 19, 2025; updated April 21, 2025.