CGG/CCG Repeat Expansions in LOC642361/NUTM2B-AS1 in Thai Patients With Oculopharyngodistal Myopathy.

Objectives: This study characterizes oculopharyngodistal myopathy in 4 Thai patients from 3 families with CGG/CCG repeat expansion in LOC642361/NUTM2B-AS1.

Methods: Repeat-primed PCR analyzed CGG/CCG repeat size in LOC642361/NUTM2B-AS1 in 4 Thai patients suspected of oculopharyngodistal myopathy (OPDM). Clinical records were reviewed for clinicopathologic features.

Results: All patients exhibited strong somatic instabilities of the expanded CGG/CCG repeats, primarily manifesting as oculopharyngeal weakness. Patient 1 had mild finger extensor and intrinsic hand muscle weakness, and although patient 2 lacked limb weakness, both siblings showed electrophysiologic evidence of distal myopathy, indicative of OPDM. Patient 3, the daughter of a sibling with OPDM reported in 2004, lacked limb weakness or leukoencephalopathy on brain MRI. Patient 4, initially misdiagnosed with refractory myasthenia gravis, had generalized muscle weakness.

Discussion: While initially characterized as oculopharyngeal myopathy with leukoencephalopathy (OPML) in a Japanese family, our study suggests a stronger association between CGG/CCG expansion in LOC642361/NUTM2B-AS1 and oculopharyngodistal myopathy (OPDM) rather than OPML. The variable presence or absence of leukoencephalopathy further supports OPDM as the predominant clinical manifestation linked to CGG/CCG expansion in LOC642361/NUTM2B-AS1.