Myospherulosis of the middle ear - a rare differential diagnosis of cholesteatoma

Background: Myospherulosis is a chronic-inflammatory lesion that is most commonly iatrogenic of origin and occurs in tissues exposed to petrolatum-based products. The disease does not exhibit characteristic symptoms and is therefore not diagnosed in some instances. In previous otorhinolaryngological studies, myospherulosis was mainly found in paranasal sinuses, while only four otitic cases have been reported. Methods: A 48-year-old female Egyptian patient suffered from bilateral chronic otitis media that had been treated in Egypt by tympanoplasty. The patient presented few months later at the university ENT department (Mainz) with deteriorated otorrhea and otalgia. Clinical, otoscopical, and radiological examination led to the diagnosis of cholesteatoma. During revision surgery of the right side, ointment-like material was found, which was embedded in granulation tissue. Middle ear biopsies were taken from both sides and routinely processed for standard histological examination and transmission electron microscopy. Results: Histological examination of the right middle ear biopsy showed cystic tissue spaces lined by histiocytes and foreign-body giant cells in a fibrous stroma. In the tissue spaces, scattered debris and sac-like structures containing round spherules of aggregated erythrocytes were found. In addition, erosion of adjacent bone matrix was seen. Diagnosis of myospherulosis was made. By contrast, histological evaluation of the left middle ear biopsy revealed cholesterol granuloma. Conclusion: Myospherulosis of the middle ear has been hitherto diagnosed in a very few otitic cases, but might be overlooked as it mimicks other chronic proliferative and inflammatory lesions such as cholesteatoma in the present case. Thus myospherulosis should be considered in otitic cases with a suspicious history (exposure to petrolatum-based products). Furthermore, patients with myospherulosis have a significantly higher likelihood of developing postoperative complications. Since the lesion exhibits distinct histological findings, microscopy plays a central role for the diagnosis of this important disease.