Introduction Allan Herndon Dudley syndrome (AHDS) is an X-linked neuropsychomotor disorder characterized by congenital hypotonia with progressive spasticity and psychomotor delay 2. It is caused by mutations in MCT8 (monocarboxylate transporter 8) which is a transporter specific for thyroid hormone T3 2. These patients have elevated serum levels of T3, low to below normal levels of free T4 and TSH is within normal range 2. We present an interesting case of a patient with AHDS leading to ventilator-dependent respiratory failure from severe tracheobronchomalacia and endobronchial polyposis which were evident on bronchoscopy. Case Presentation Our patient is a 22-year-old male with a past medical history of Allan Herndon Dudley Syndrome who presented to the hospital with complaints of productive cough, fever, and vomiting. The patient was febrile, tachycardic, and hypoxic requiring 2L oxygen supplementation via nasal cannula. Chest X-ray revealed perihilar infiltrates. Upon further questioning, the patient’s caregivers endorsed that the patient had been producing high-pitched squealing sounds with respirations for a prolonged period of time with ongoing issues of aspiration of oral secretions. Subsequently, the patient was started on Ampicillin/Sulbactam for aspiration pneumonia. The hospital course was complicated with worsening hypoxia and increased work of breathing. Despite steroids, the patient desaturated to 60% which prompted intubation. Repeat chest X-ray revealed worsening bilateral patchy airspace opacities. Multiple attempts were made to wean the patient off of the ventilator but failed and eventually tracheostomy was done. Hypoxic episodes persisted and the patient then underwent bronchoscopy which revealed severe tracheobronchomalacia with endobronchial polyposis requiring custom length bivona hyperflex tracheostomy acting as a tracheal stent. After bivona tracheostomy placement, the patient had no further hypoxia episodes and was eventually discharged to long-term acute care hospital. Discussion AHDS causes decreased thyroid hormone uptake in the brain leading to developmental disabilities. The disease features include neurological, developmental, and psychomotor irregularities such as central hypotonia, ataxia, paralysis, aphasia, non-epileptic paroxysmal movement disorders, spastic paraplegia, and intellectual disability 1. The syndrome also causes thyroid irregularities including poor weight gain, reduced muscle mass, cold intolerance, tachycardia, and constipation 1. Per our review of the literature, there have been no reported cases of AHDS with pulmonary complications yet. Our patient was found to have severe tracheomalacia and endobronchial polyps requiring custom-made tracheostomy. Hence, bronchoscopic evaluation may be necessary for AHDS patients who have hypoxia despite medical management to evaluate for tracheobronchomalacia and endobronchial polyps as it can reduce the length of hospital stay with appropriate management. References 1. Beheshti, R., Aprile, J., & Lee, C. (2022). Allan-Herndon-Dudley Syndrome: A Novel Pathogenic Variant of the SLC16A2 gene. Cureus, 14(1), e21771. https://doi.org/10.7759/cureus.21771 2. Sarret C, Oliver Petit I, Tonduti D. Allan-Herndon-Dudley Syndrome. 2010 Mar 9 Updated 2020 Jan 16. In: Adam MP, Feldman J, Mirzaa GM, et al., editors. GeneReviews® Internet. Seattle (WA): University of Washington, Seattle; 1993-2024. Available from: https://www.ncbi.nlm.nih.gov/books/NBK26373/