Treating Hypotonia

Treating Hypotonia

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Outgoing teen Meredith Zanelotti has been able to remain active through management of her low muscle tone and underlying genetic disorder at the Johns Hopkins Hypotonia Center.

Many patients with low muscle tone go undiagnosed and untreated for months or years, leaving parents feeling lost in a system with no real answers.

In 8th grade, Meredith Zanelotti came down with a bad case of the flu, so bad that she had trouble walking in her Ellicott, Md., home. Her flu passed but from then on her parents noticed that she experienced severe pain in her legs after each soccer practice. Interestingly, the pain subsided after Meredith downed her usual post-practice snacks and Gatorade. Her Highland, Md., pediatrician, Mel Stern, puzzled by the strange symptoms and their response to the snacks, suspected they had genetic rather than skeletal origins. Indeed, at Johns Hopkins tests revealed that Meredith had Carnitine Palmitoyltransferase (CPT) II Deficiency, an extremely rare genetic disorder characterized by recurring episodes of muscle-fiber breakdown, which explained the girl’s lower limb pain. Pediatrician/geneticist Ronald Cohn, an expert on hypotonia, quickly figured it out.

“Dr. Cohn was an angel who fell out of the sky,” says Meredith’s mother, Gail Zanelotti. “When I told him food seemed to make her muscle pain go away, he put two and two together.”

Cohn explains that for CPT II Deficiency patients like Meredith, multiple triggers – from exercise to a virus – can set off the painful breakdown of muscle tissue. Loading up on carbohydrates has the effect of normalizing muscle metabolism and suppressing any muscle aches. But too often, Cohn says, such symptoms can mask as orthopedic or rheumatologic conditions, delaying diagnosis and treatment. He adds that community pediatricians are generally good at detecting signs of hypotonia and appropriately referring patients to pediatric neurologists or developmental pediatricians (see story page 6). But there is no one place where these patients can receive a comprehensive workup with an eye on both physical and genetic causes in diagnosing patients, which explains why Cohn led the development of the Johns Hopkins Hypotonia Center, the only such center in the world.

“Through my residency and clinical experience,” Cohn says, “I realized a whole lot of patients out there have low muscle tone and not necessarily a skeletal-muscle disorder.”

In fact, hypotonia is associated with over 600 known genetic conditions, and potentially many more yet unnamed conditions. Center staff like genetic counselor Emily Lisi, Cohn explains, have the ability to look beneath the surface of hypotonia and identify these often more serious underlying conditions, which otherwise go undetected and untreated with dire results. CPT II Deficiency, for example, can lead to life-threatening kidney failure, though many people with the disorder are completely unaware of its existence until they undergo genetic testing. Similarly, genetic testing of hypotonia patients has led to the identification of chromosomal abnormalities like Williams Syndrome and related structural problems in the brain, heart and kidney, among other organs. Such clinical information, Lisi notes, is also helpful for parents who are thinking about having more children.

“In addition to providing recurrence risk information, diagnosing the underlying genetic condition is important for giving parents a clearer picture of what may be in store for them in the future,” says Lisi.

Drawing more patients through the Center has also allowed Cohn and Lisi to classify patients, improving diagnostic and therapeutic options. Some patients, like 4-year-old Laneah Whiddon of Bowie, Md., suffer severe hypotonia with breathing and swallowing problems, and with no clear underlying disorder or cause of the hypotonia. The Center’s approach, Cohn says, is to empathize with parents and take the burden of diagnosis off their shoulders.

“I tell parents that while I continue to chase the diagnosis, at the same time we’ll continue to focus on the management of the child,” Cohn says. “The majority of parents appreciate not having to worry too much about what it is. Whether or not you have a diagnosis, together we will manage the child the best we can.”

His patients’ parents agree. “He’s been there to guide me on what to do and what not to do,” says Laneah’s mother, Dana Whiddon. “Without him, I’d feel pretty lost.”

“He’s been our go-to guy,” says Gail Zanelotti. “He’s allowed us to see the whole picture.”

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