Pupillary dysfunction in an atypical case of mitochondrial myopathy with tubular aggregates

A 62-year-old man presented with diplopia, ocular ductional deficits, and sluggish pupils. Pupillometry demonstrated large hyporeactive pupils with no evidence of damage to the sympathetic or parasympathetic innervation, indicating a myopathy of the iris musculature. A single large deletion in mitochondrial DNA and characteristic histochemical features on muscle biopsy suggested a mitochondrial cytopathy. However, ultrastructural examination of skeletal muscle fibers showed tubular aggregates (TAs), a finding not reported in mitochondrial cytopathy. The combination of pupillary abnormalities and TAs suggests that mitochondrial dysfunction may not explain the full extent of abnormalities in this case.