SAVANNAH, GEORGIA — At a pathophysiological level, juvenile myasthenia gravis (MG) seems to be identical to the adult form, neuromuscular specialists learned. But there are still important differences between children and their elders that affect pediatric care.
For example, “we have to think a little bit differently about the side effect profiles of the medications and their toxicity because children may react to medications differently,” said Matthew Ginsberg, MD, a pediatric neurologist based in Akron, Ohio, in a presentation at the American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) 2024.
And then there’s the matter of adherence. “It’s hard to get adults to take medication, but a teenager is sometimes an exceptional challenge,” Ginsberg said.
Case In Point: A 13-Year-Old With MG
Pediatric MG is rare. Cases in children are estimated to account for 10% of MG cases diagnosed each year. According to a 2020 report, “the majority will present with ptosis and a variable degree of ophthalmoplegia [paralysis of eye muscles].”
Ginsberg highlighted a case of a 13-year-old girl who’d been healthy but developed fatigable ptosis and mild restriction of extraocular movements. The patient’s acetylcholine receptor antibodies were very elevated, but she didn’t have MuSK antibodies.
“This isn’t a diagnostic conundrum. She has autoimmune myasthenia gravis with ocular manifestations,” Ginsberg said. “For someone like this, whether it’s an adult or a child, many people would start symptomatic treatment with an acetylcholinesterase inhibitor like pyridostigmine.”
The use of the drug in children is similar to that in adults, he said, although weight-based dosing is used. “Usually it’s around 3-7 mg/kg/d, but it’s still very individualized based on patient response.” The timing of symptoms can affect the distribution of doses throughout the day, he said.
“There are extended-release formulations of the medication, and I think some people use them more than I do,” he said. “The side effects are basically similar to adults. Most of the patients I have on it tolerate it really well and don’t have a lot of the muscarinic side effects that you would expect.”
Consider Prescription Eye Drops for Ptosis
Alpha-1A agonists oxymetazoline and apraclonidine in the form of topical eye drops can help with ptosis. “They potentially avoid some of the systemic toxicity of the other medications,” Ginsberg said. “So they might be an option if you’re really just trying to target ptosis as a symptom.”
However, it can be difficult to get insurers to cover these medications, he said.
The 13-year-old patient initially improved but developed difficulty walking. “Her hands began to feel heavy, and she had difficulty chewing and nasal regurgitation. On her exam, she still had fatigable ptosis plus hypernasal speech and generalized weakness. At this point, we’re starting to see that she has generalized myasthenia gravis that may be an impending crisis.”
The Young Patient Worsens. Now What?
The patient was admitted and given intravenous immunoglobulin at 2 g/kg over a couple days. But her symptoms worsened following initial improvement.
Glucocorticoids can play a larger role in treatment at this stage, and the patient was initially on prednisone. But there are reasons for caution, including effects on bone growth and interference with live vaccines.
However, live vaccines aren’t common in children, with the exception of the MMRV vaccine, he said. “It’s worth noting that you can give that second dose as early as 3 months after the initial one, so most patients really should be able to complete a course before they start on immunosuppression,” he said.
Another option is immunotherapy. “There’s a really large menu of options for immunotherapy in myasthenia gravis right now,” Ginsberg said. “It’s great that we have all these options, but it adds to the complexity.”
Rituximab may be considered based on early data, he said. And thymectomy — removal of the thymus gland — should be considered early.