Columbia Neurologist Transforms Child Muscle Disease Outlook

Experimental treatment gives new hope to patients with rare, fatal genetic disorder

Published on Feb. 28, 2026

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When Arthur Estopiñan's 18-month-old son Arturito was diagnosed with a rare and usually fatal genetic disorder that rapidly weakens and destroys muscles, doctors told the family there was no treatment. But Columbia neurologist Michio Hirano had developed an experimental therapy that ended up transforming Arturito's outlook, allowing him to regain motor functions and attend school. The treatment, now approved by the FDA, has dramatically improved survival rates for patients with this condition.

Why it matters

This story highlights the potential for scientific breakthroughs to transform outcomes for patients with rare, devastating genetic diseases. The successful development of this treatment, which was made possible through collaboration between dedicated families, doctors, scientists, and companies, offers hope for addressing the over 400 known mitochondrial diseases that collectively affect about 1 in 5,000 people.

The details

Hirano created a line of mice with the TK2 enzyme deficiency disorder that Arturito had, which allowed him to test potential treatments. He found that administering certain compounds could restore mitochondrial health and prevent muscle cell degeneration. When Arturito came to Hirano's clinic in 2012, he was in the terminal stage of the disease and couldn't move his limbs. After receiving the experimental therapy, Arturito slowly regained motor functions, and by age 10 he was riding a tricycle. The treatment was eventually approved by the FDA in 2025 for TK2 deficiency patients whose symptoms emerge by age 12, dramatically improving survival rates.

  • In 2012, Arturito Estopiñan was diagnosed with the rare genetic disorder at 18 months old.
  • In the early 2010s, Hirano created a mouse model of the TK2 deficiency disorder to test potential treatments.
  • By 2019, Hirano had treated about 20 patients and opened a phase 2 clinical trial for the therapy.
  • The FDA approved the therapy, now called KYGEVVI, in November 2025 for TK2 deficiency patients whose symptoms emerge by age 12.
  • As of 2026, over 100 patients are now being treated with the approved therapy.

The players

Michio Hirano

A Columbia neurologist who developed an experimental treatment for the rare genetic disorder that Arturito Estopiñan had.

Arthur Estopiñan

The father of Arturito Estopiñan, who was diagnosed with a rare and usually fatal genetic disorder that rapidly weakens and destroys muscles.

Arturito Estopiñan

An 18-month-old boy who was diagnosed with a rare genetic disorder that rapidly weakened and destroyed his muscles, but was given a second chance at life through Hirano's experimental treatment.

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What they’re saying

“Dr. Hirano said he had an experimental treatment, and I nearly fell out of my chair. I repeated the diagnosis to make sure he had understood. He said, 'I understood what you said. And yes, we have a clinical path forward.'”

— Arthur Estopiñan (Mirage News)

“When Arturito came to us, he was in terrible condition, unfortunately, and in the terminal stage of the disease. He couldn't lift his arms or legs, he couldn't lift his head; he was like a rag doll.”

— Michio Hirano, Columbia Neurologist (Mirage News)

“Obviously, without this treatment, my son would not be here today. Dr. Hirano and his team gave my son a second chance at life.”

— Arthur Estopiñan (Muscular Dystrophy Association)

What’s next

Hirano continues to search for even better treatments and has found that, in mice, a gene therapy combined with the drug therapy is markedly more effective. He is also testing a different therapy for another rare mitochondrial deficiency disease.

The takeaway

This story demonstrates the power of scientific collaboration and perseverance to transform the outlook for patients with rare, devastating genetic diseases. The successful development of this treatment for TK2 deficiency offers hope that similar breakthroughs can be achieved for the over 400 known mitochondrial diseases that collectively affect a significant number of people.