Report of progressive myoclonus ataxia (PMA) in two Chinese pedigrees

To describe the clinical characteristics of patients diagnosed with progressive myoclonus ataxia (PMA) from two Chinese pedigrees.

An analysis of clinical data is presented and inferences drawn.

The propositus from pedigree-I (9-year-old female) could not walk stably and had a history of frequent falls. The symptoms aggravated over time until she lost the ability to take care of herself. Her physical and mental development (including cognitive ability) was normal. She had an ataxic gait, ataxic dysarthria, bilateral horizontal nystagmus and visible limb myoclonus. She failed the bilateral finger-to-nose and heel-knee-tibia tests and could not walk in a straight line. Babinski signs were not observed. EEG tracing during sleep showed low-amplitude spikes and spike-and-slow waves in the bilateral frontal and mid-frontal areas. Her magnetic resonance imaging scan was normal. In pedigree-II, the propositus (a 54-year-old male) could not walk stably and had a history of occasional falls for the past 34 years. The symptoms aggravated gradually until he lost the ability to perform routine daily activities. There was no history of convulsions. His physical and mental faculties, as well as the neurological findings were similar to those of the pedigree-I. Both proposituses did not respond well to symptomatic treatment. A novel mutation has been identified in SGCE gene (NM_003919:exon3:c.360delT:p.A120fs) using exome sequencing.

PMA patients from the two pedigrees had autosomal dominant mode of inheritance, with variability in the age of onset and disease severity. The cardinal symptoms were myoclonic seizures and ataxia without mental retardation.