Dr. Keith Roach

DEAR DR. ROACH: You have written about immunocompromised people before, but what about those of us who have immune systems that overreact instead of underperform, such as with Guillain-Barre syndrome? What is the likelihood of this happening again, and what precautions should one take? I didn’t recover completely and fear having the myelin sheath stripped from my nerves again. — L.H.
ANSWER: There are many autoimmune diseases, such as GBS, where the body attacks one, or more, specific cell types of the body. With GBS, it’s the myelin, a protein that surrounds and protects nerves, that is the target of the body’s attack. The major symptom is progressive weakness, which sometimes includes paralysis of the respiratory muscles, requiring ventilatory support (i.e., a ventilator or breathing machine).
Most cases (about 75%) have a trigger that occurs about four weeks prior to their attack of GBS. A respiratory infection (such as influenza) is most common, followed by gastroenteritis. Vaccination is often considered a risk, but the risk of being diagnosed with GBS after vaccination is about one person per million vaccinations.
I can’t answer how to prevent reocurrence of all autoimmune diseases, as the strategies are specific to each disease, but for GBS, reocurrence is rare, with only about 5% of patients who’ve made a recovery experiencing a recurrence. The Miller Fisher variant of GBS, consisting of paralysis in the eye muscles and dizziness, is more likely to reoccur than GBS. Treatment is indicated for severe or progressive symptoms during the acute event, but I don’t know of any treatment specifically for preventing reoccurrence.
Most experts believe that the risk of relapse following an influenza infection is so much larger than the risk from vaccination. So, patients with GBS should get regular vaccines, but that is ultimately a discussion between you and your neurologist.
DEAR DR. ROACH: I am not opposed to genetically modified organisms in general, but I am wondering how they might affect my niece, who has phenylketonuria (PKU). Has there been any moves to insert animal genes into fruits or vegetables to give them a protein boost for vegetarians and vegans? I can imagine this happening as more people switch to a plant-based diet. Is it possible? Is anyone working on it? And how would someone know if the vegetable they bought contains animal genes? — S.M.
ANSWER: PKU is a genetic disease caused by a deficiency of the enzyme phenylalanine hydroxylase. Phenylalanine is an amino acid, a component of proteins. With a deficiency of the enzyme, phenylalanine and its metabolites can build up in the blood and damage the brain cells. By avoiding excess phenylalanine (a small amount is safe), especially in early development, brain development will continue like normal (or nearly so), and people like your niece can still have normal brain function.
Of course, the diagnosis must be made right away, which is why PKU is universally screened for at birth. PKU is not that rare, with one in 10,000 people receiving a diagnosis in European populations. High-protein foods must be avoided, and amino acid supplements are given as medical foods.
People with PKU need to avoid high amounts of phenylalanine their whole lives, so I understand why you are concerned that safe foods, like fruits and vegetables, could become unsafe by genetic manipulation. But that kind of genetic modification does not currently exist, and I do not think it will. If anything, genetic modifications might improve life for people with PKU. I read of a genetically-modified probiotic that breaks down phenylalanine before it is absorbed in the gut.
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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.
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