Distal oculopharyngeal myopathy (DOPM) type 4 is due to a CGG repeat expansion in the RILP1 gene. First described in 2022, it has only been reported in four Chinese families. It manifests as ptosis in the third decade, ophthalmoplegia between the ages of 25 and 35, and dysphagia and dysarthria between the ages of 30 and 40. The age of onset of distal lower limb deficit varies.
In the description of the fifth family which has just been published, also by a Chinese team:
- eight members were affected;
- most presented with distal lower limb muscle weakness and a reduction in walking ability between the ages of 20 and 30;
- followed by ptosis, ophthalmoplegia and swallowing problems;
- a later loss of walking ability between the ages of 50 and 70.
Muscle biopsy of the index case, a 53-year-old woman, revealed a fibroadiputic transformation with multiple eosinophilic intranuclear inclusions positive for protein p62; her muscle MRI showed severe adipose infiltration of the pelvic girdle and lower limb muscles.
