Abstract Introduction Distal hereditary motor neuropathy type 7B(DHMN7B) due to a mutation in the dynactin 1 gene(DCTN1); is a recognised cause of neurodegeneration presenting in the 3rd-4th decade(1). A rare cause of respiratory compromise due to vocal cord paralysis, hypoventilation and respiratory failure, physician awareness is critical for timely diagnosis and prevention of sudden death given expectant normal longevity with appropriate medical management. We present a case of DHMN7B initially presenting with dyspnoea attributable to vocal cord paralysis and stridor. Case report A 44 year old female never smoker presented to the Emergency Department(ED) with dyspnoea, productive cough and wheeze. Past medical history included psoriatic arthritis and degenerative spinal disease. Family history included DHMN7B affecting a first cousin and a paternal history of COPD and suspected motor neurone disease. She was managed initially as a new diagnosis of adult onset asthma with inhaler therapy and discharged with outpatient Respiratory follow up. Spirometry, FENO, eosinophils and room air arterial blood gas were normal. Genetic self- referral resulted in confirmation of DCTN1 carrier(c.175GA variant). Subsequent Neurology review revealed evidence of bilateral vocal cord involvement, stridor and facial fasciculation. She later described nocturnal gasping, day time somnolence and fatigability. Pulmonary function testing demonstrated respiratory muscle weakness with fall in lying and standing FVC of 13% however overall preservation of FVC 3.79L. Maximum inspiratory pressures significantly reduced at -33cmH20. Flow volume loop absent peak suggestive of some extra thoracic upper airway obstruction. Laboratory polysomnography showed a normal apnoea hypoapnoea index of 4. ENT flexible nasendoscopy depicted restrictive vocal cord movements. Nocturnal non- invasive ventilation (NIV) was commenced as a bridge to elective tracheostomy given severity of symptoms. However, given rapid progressive stridor and failure of NIV response inpatient admission followed for emergent tracheostomy with expectant NIV cessation following tracheostomy placement. Discussion DHMN7B true incidence globally is unknown with limited literature availability. This case underscores the need for clinician vigilance and a high index of suspicion especially in those with a significant family history given its autosomal dominant nature with high penetrance and stereotyped presentation with early vocal cord weakness. Consideration of stridor in those with dyspnoea and coinciding neurological symptoms is key; diagnosis and timely airway management being critical to normal life expectancy. References 1.Wustl.edu. (2022). Hereditary Motor Syndromes. online Available at: https://neuromuscular.wustl.edu/synmot.html#vocaldyn This abstract is funded by: nil
Gillen et al. (Fri,) studied this question.