Eye Movement Condition Nystagmus May Be Feature of Infantile Pompe, Report Shows
The report, “Nystagmus in Infantile Pompe Disease: a new feature?” was published in the journal Acta Bio Medica.
Pompe disease is caused by mutations that limit the body’s ability to break down the complex sugar molecule glycogen, which causes it to build up in the body’s tissues. Glycogen primarily accumulates in muscles, resulting in symptoms such as muscle weakness and heart problems. However, glycogen buildup also may impact other parts of the body, in ways that are still not fully understood.
Eye problems, including refractive errors such as near- and farsightedness and related conditions, ptosis or eyelid drooping, and strabismus — when the eyes do not line up with each other — have previously been reported in infants with Pompe. In contrast, nystagmus has rarely been described in people with the inherited disorder.
Now, researchers at the University-Hospital of Parma, in Italy, described the case of a 3-month-old girl who was transferred to their hospital due to hypertrophic cardiomyopathy, or enlarged heart muscles — a common symptom of Pompe disease. Other clinical findings included muscle weakness, failure to thrive, and difficulty breathing and eating. The baby had been born to biologically related (consanguineous) parents after an uneventful pregnancy.
During a neurological examination, the researchers described impaired eye tracking, as well as involuntary, rhythmic, and multi-directional oscillation of the eyes — that is, nystagmus. Other eye problems, such as ptosis, were not noted.
A chest examination on the baby revealed coarse breathing sounds. Further analyses also found liver enlargement and elevated levels of creatine phosphokinase, an indicator of muscle injury. The little girl also had elevated levels of the enzymes alanine transaminase and aspartate aminotransferase, two markers of liver damage.
The presence of hypertrophic cardiomyopathy and muscle weakness, combined with results from lab tests and a delay in achieving motor milestones, led the researchers to suspect that the baby had infantile Pompe disease. This diagnosis was confirmed with subsequent laboratory and genetic tests.
After being diagnosed, the baby was transferred to another hospital to begin enzyme replacement therapy (ERT). She died shortly after, following cardiovascular complications.
Little is known about how the brain is affected in Pompe disease, the investigators said, because most people born with the condition have died before brain effects could be meaningfully investigated. With new treatment paradigms such as ERT, more about how Pompe disease affects the body may be learned in the future.
“In this paper we highlight an ocular sign, whose uncertain pathogenesis [disease processes], rarely described before, must be taken into consideration, because by now, with increasing survival with ERT, a new phenotype [manifestation] of Pompe disease is taking shape,” the researchers concluded.