Background: A link between progressive dental malocclusion, the use of a continuous positive airway pressure mask and GH-secreting pituitary macroadenoma (acromegaly) has not been previously reported. The present clinicopathological analysis stresses that tooth malposition should not be seen exclusively as a local process. Case Presentation: A 62-year-old caucasian man with no relevant medical history reported difficulty chewing food and perceived voice alteration during his annual periodontal check-up. He also referred stiffness of the tongue, face, and submandibular area. The patient had been diagnosed with obstructive sleep apnea syndrome two years previously, since when he had worn a continuous positive airway pressure device during sleep. Exploration of the occlusion revealed significant changes: an atypical left lateral and anterior open bite with major buccoversion of teeth 33, 34, 35, 36. Inspection of the soft tissue revealed only macroglossia, although external palpation indicated a subcutaneous stiffness of the submandibular area. General analytical tests, including hormone profiles, and magnetic resonance imaging confirmed the diagnosis of acromegaly induced by a pituitary adenoma. Intrasellar tumor resection via transsphenoidal approach was performed. After surgery, the patient already noted a marked improvement of all symptoms associated with the acromegaly. Desaturation data also evolved favourably and the pulmonologist advised the patient to abandon the continuous positive airway pressure treatment. Conclusion: Progressive dental malocclusion may be associated with a systemic disease and the use of a nasal mask with premaxillary support may distort the diagnosis of acromegaly.