Author response: IgLON5-mediated neurodegeneration is a differential diagnosis of CNS Whipple disease

Abstract

We thank Drs. Bally and Lang for their interest in our report,1 and for alerting clinicians to the fact that palatal tremor (PT) occurs in only a minority of patients with neurologic Whipple disease (WhD). Drs. Bally and Lang also point out that PT occurred in the absence of olivary pseudohypertrophy in WhD. Interestingly, olivary pseudohypertrophy was also absent in our patient with IgLON5, as well as a patient with IgLON5 and cranial myorhythmia reported by Honorat et al.2 Drs. Bally and Lang also suggest that the absence of vertical gaze palsy makes WhD a less likely possibility. While we agree, the presence of vertical gaze palsy does not distinguish between the 2 conditions, as vertical gaze palsy is also reported in 27% of patients with IgLON5.3 The combination of myorhythmia and myoclonus in our patient was reminiscent of neurologic WhD, but the presence of sleep apnea—and eventually severe sleep disturbance—was the trigger to consider IgLON5. Both IgLON5-mediated neurodegeneration and WhD may rarely present with PT, vertical supranuclear gaze palsy, and normal MRI. While facial spasms are increasingly recognized in IgLON5,3 it may be that oculomasticatory myorhythmia is the most specific neurologic sign of WhD.4,5