Mycoplasma pneumoniae (MP) is a common cause of respiratory infections and can be associated with extrapulmonary complications. MP mucositis has recently been described as a distinct endemic clinical entity called Mycoplasma pneumoniae-induced rash and mucositis (MIRM). The authors present the case of a 46-year-old man with atypical pneumonia associated with exuberant mucositis, conjunctival hyperaemia and positive serological assays for MP IgM. The patient was treated with azithromycin and systemic corticosteroid therapy. Supportive care including pain management, intravenous hydration and mucosal care was also given. There was complete resolution of the pneumonia and mucositis. The presence of atypical pneumonia with mucosal involvement without cutaneous lesions and a favourable clinical evolution led to the diagnosis of MIRM.LEARNING POINTSMycoplasma pneumoniae infection can be associated with mucocutaneous lesions. A new entity called Mycoplasma pneumoniae-induced rash and mucositis (MIRM) has been recently described. The mucocutaneous involvement associated with MIRM is predominantly mucositis with scarce or absent cutaneous expression.The clinical presentation, pathophysiology and disease outcomes of MIRM distinguish it from Stevens-Johnson syndrome/toxic epidermal necrolysis and erythema multiform.MIRM has an overall favourable prognosis as the majority of patients recover without sequalae and recurrence is rare.

Enlarged mitochondria and intramitochondrial dense structures have been reported to occur in a great variety of animal and human cells under normal, pathologic, and experimental conditions. Three cases of benign thyroid lesions are described in which large cytoplasmic inclusions were seen on light microscopy. These inclusions were stained with toluidine blue but not with Sudan black B, as was seen in consecutive sections. Ultrastructural observation showed that they corresponded to giant mitochondria. Bundles of dense filaments and round, electron-dense bodies were observed in the matrix of the enlarged mitochondria. Incubation of ultrathin sections with proteolytic enzymes (pepsin, trypsin, and type XVI-protease) led to a striking decrease in the electron density of both types of intramitochondrial matrical structures. These observations demonstrate that a major proteic component exists in intramitochondrial filamentous bundles and in dense bodies.

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