Standing in the small room, we waited for the doctor. I couldn't tell you how many times we had repeated this scene over the past 16 years, and each time was the same. The doctor would measure our son's head circumference, check his reflexes and tone, see if he responded to various stimuli, and then ask about his behavior and whether he'd had any seizures lately.

We'd been coming to this room and others like it since my son was five months old. We had added a host of doctors to our roster: neurologists, gastroenterologists, nephrologists, orthopedists, and geneticists. As the years progressed, we learned about social services, special education, and the need to apply for guardianship for our own child.

We took our son from doctor to doctor to address his symptoms: an unusually small head (microcephaly), multiple ear infections, months of diarrhea followed by years of chronic constipation, missed developmental milestones, and, as he neared three years old, multiple seizures. One doctor told us, "He'll never walk and he'll be a vegetable." We never returned.

As our baby grew into a young man, we learned to be our child's most vocal advocate, making difficult choices about testing. And there were lots of tests: magnetic resonance imaging scans, electroencephalograms, as well as more specific genetic and metabolic tests. We weren't just looking for a diagnosis—we were looking for information that would help with his treatment, and, in the early years, to help us decide whether to have another child. The physicians believed the cause was genetic, but had no proof. When we decided to have another child, seven years later, we felt like we were playing genetic Russian roulette. Our second boy is now a healthy 10-year-old.

When you have a profoundly disabled child, there is an equally profound sorrow. With or without a diagnosis, the moment you understand the severity of the disability marks the death of all the hopes and dreams you ever had for that child. It's the realization that this special child of yours will never graduate, go to college, fall in love, get a job, or have his own children. He'll never truly grow up.

Yet, as we watched him grow, the jagged edges of our sorrow diminished like a stone in the river, becoming more rounded and worn with time. We found tremendous joy in our shared lives. I remember his first steps, in splints and a helmet, in the middle of a store. As I cheered him on with tears in my eyes, so did a number of other parents who had realized the very special moment they were witnessing. Though he has few words, it is clear that my son finds joy in the world around him and in the people who love him as he loves them.

When his neurologist entered the room that day and said, "So, I see we have a diagnosis," my husband and I were stunned. We'd long given up on a diagnosis and now, after all this time, we had one.

My son has Mowat-Wilson syndrome, a rare genetic disorder. The condition typically includes distinctive facial features, intellectual disability, delayed development, and an intestinal disorder called Hirschsprung disease, among other birth defects. We finally have a diagnosis, but little can be done about it. Even less is known about the prognosis for these children.

Having this diagnosis after 16 years has had an impact on us beyond what I could have imagined. We now know that the seizures, which finally calmed down as he entered puberty, are likely to remain more manageable. My younger son has found a way to connect with his older brother now that he has something tangible to point to as he comes to grips with why this happened. And the niggling, albeit irrational, question lingering in the back of my mind—whether I could have done something to change things—disappeared in a flash, freeing me to experience more of the joy of being with my son, even if that weathered stone of sorrow remains.