Myoclonus and Gaze Palsy in Childhood-Onset <i>SQSTM1</i>-Related Neurodegeneration

Jacky Ganguly; Sayoni Roychowdhury; Rohit Keshav; Debayan Dutta; Soumava Mukherjee; Purba Basu; Hrishikesh Kumar

doi:10.14802/jmd.26164

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Teaching Video Myoclonus and Gaze Palsy in Childhood-Onset SQSTM1-Related Neurodegeneration: Jacky Ganguly, Sayoni Roychowdhury, Rohit Keshav, Debayan Dutta, Soumava Mukherjee, Purba Basu, Hrishikesh Kumar; Journal of Movement Disorders 2026;19(3):363-364.
DOI: https://doi.org/10.14802/jmd.26164
Published online: July 6, 2026

Department of Neurology, Institute of Neurosciences Kolkata, Kolkata, India

Corresponding author: Jacky Ganguly, MD, DM, PDF Department of Neurology, Institute of Neurosciences Kolkata, 185, Acharya Jagadish Chandra Bose Rd, Elgin, Kolkata 700017, India / Tel: +91-3366579999 / E-mail: jackyganguly03@gmail.com

• Received: May 25, 2026 • Revised: June 24, 2026 • Accepted: July 5, 2026

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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A 15-year-old girl, born to nonconsanguineous parents, presented with 1 year of progressive behavioral decline and abnormal movements. She developed irritability, depressive episodes, and cognitive deterioration with declining academic performance, and increasing jerky movements involving the hands. Examination revealed impaired attention, episodic memory and executive dysfunction (MoCA 22/30) with vertical gaze limitation, myoclonus, dystonia and ataxia. Brain MRI showed mild cerebellar atrophy (Figure 1). Whole-exome sequencing revealed a homozygous pathogenic SQSTM1 frameshift variant (c.823_ 824del; p.Ser275PhefsTer17) (PS4, PVS1, and PM2). SQSTM1/p62 functions as a multidomain scaffold protein involved in selective autophagy, oxidative stress response and intracellular signaling pathways [1]. Recent reports have expanded the phenotypic spectrum of biallelic SQSTM1-related neurodegeneration with ataxia, dystonia and gaze palsy (NADGP), including vertical supranuclear gaze palsy, oculomotor apraxia and bilateral internuclear ophthalmoplegia with intrafamilial phenotypic variability [2-4]. SQSTM1-related disease should be considered in the differential diagnosis of progressive childhood-onset movement disorders with Niemann–Pick disease type C-like phenotypes.

Supplementary Materials

The Data Supplement is available with this article at https://doi.org/10.14802/jmd.26164.

Supplementary Video 1.

Oculomotor examination demonstrated slow saccades, gaze restriction (vertical>horizontal, predominant downgaze restriction) with bilateral horizontal gaze-evoked nystagmus. The patient exhibited jerky, arrhythmic, distal-predominant myoclonus involving both upper limbs, present at rest but more prominent during posture and action. The jerks were not stimulus-sensitive to tactile or auditory stimuli. Dystonic posturing of the outstretched hands was also noted. Dysmetria noted on left upper limb while doing the finger-nose test, along with some difficulty in tandem gait.

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Ethics Statement

The authors confirm that the approval of an institutional review board was not required for this work. We also confirm that the patient has given written informed consent for the publication of his clinical details, imaging, and video.

We confirm that we have read the Journal’s position on issues involved in ethical publication and affirm that this work is consistent with those guidelines.

Conflicts of Interest

The authors have no financial conflicts of interest.

Funding Statement

None

Acknowledgments

We acknowledge the patient and her caregivers for their constant support.

Author Contributions

Conceptualization: Jacky Ganguly, Sayoni Roychowdhury. Formal analysis: Rohit Keshav, Debayan Dutta, Soumava Mukherjee, Purba Basu. Investigation: Rohit Keshav, Debayan Dutta, Soumava Mukherjee, Purba Basu. Supervision: Hrishikesh Kumar. Writing—original draft preparation: Jacky Ganguly. Writing—review & editing: Sayoni Roychowdhury, Hrishikesh Kumar.

Figure 1.

MRI brain T2 axial (A and C) and T2 sagittal images (B) showing mild cerebellar atrophy.

REFERENCES

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2. Sharma C, Ganguly J, Madan D, Chowdhury SR. Bilateral internuclear ophthalmoplegia in childhood-onset SQSTM1-related neurodegeneration: expanding the clinical spectrum. Mov Disord Clin Pract 2026;13:1568–1570.PubMed
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