OBJECTIVE: To present the case of a patient with otomastoiditis with poor clinical significance that evolved with a mixed hearing loss. CASE: C.L.S, 67 year old, male, complaining of hearing loss for 10 days after frame of IVAS, reported mild otalgia, autophonia and fullness in her left ear (OE). Presented co morbidities: diabetes, hypertension, uncontrolled and dyslipidaemia. Otoscopy: opacity of the MT to the OE. And impedance audiometry: hearing loss in the left ear and severe mixed type curve B. Due to the possibility of involvement of the membranous labyrinth, we proceeded to hospitalization, intravenous antibiotic therapy with Ceftriaxone and steroids. It was realized computed tomography of the ear: presence of opacification of soft tissue density of the mastoid and tympanic cavity. No improvement after 48 hours of clinical treatment was performed timpanomastoidectomy closed cavity and placement of tympanotomy tubes. The patient recovered well and was discharged on the second day after surgery. CONCLUSION otomastoiditis as a complication of OMA can evolve atypical and oligosymptomatic in order to remain hidden so that the otologist should have a false sense of security regarding the presence of milder symptoms and should be alert to signs of involvement of the ear internal, especially in patients with co morbidities.