TUBB3 E410K syndrome with osteoporosis and cough syncope in a patient previously diagnosed with atypical Moebius syndrome.

Background: A heterozygous c.1228G > A p.E410K mutation in TUBB3 encoding neuronal-specific β-tubulin isotype 3 causes TUBB3 E410K syndrome, which exhibits a wide range of neurological and endocrinological abnormalities.

Case Description: The patient is a 31-year-old Japanese woman who was diagnosed with atypical Moebius syndrome because of congenital facial weakness and extraocular ophthalmoplegia sparing abduction. She suffered a femoral neck fracture at 23 years of age, and radiological and endocrinological studies revealed osteoporosis because of hypogonadotropic hypogonadism. She also had borderline intellectual disability, cyclic vomiting, syncope with cough, and decreased sense of smell since childhood. Brain magnetic resonance imaging revealed abnormal morphology of the corpus callosum and pontine. Hypoplastic bilateral oculomotor and facial nerves were evident. Based on these symptoms, we analyzed the TUBB3 gene and identified a heterozygous c.1228G > A (p.E410K) mutation that confirmed the diagnosis of TUBB3 E410K syndrome.

Conclusion: TUBB3 E410K syndrome may be diagnosed as atypical Moebius syndrome because of overlapping clinical symptoms. Genetic analysis of c.1228G > A in TUBB3 is useful to differentiate TUBB3 E410K syndrome from other disorders presenting congenital external ophthalmoplegia and facial nerve palsy.