Multi-system mitochondrial disorder with recurrent steroid-responsive eosinophilia.

Though mitochondrial disorders due to a respiratory chain defect may manifest with haematological abnormalities such as anaemia, neutropenia, or thrombocytopenia, recurrent steroid-responsive eosinophilia has not been reported as a manifestation of a mitochondrial disorder. In a polymorbid 65-year old female recurrent erythema, asthma, chronic bronchitis, gastritis with eosinophilic granuloma, recurrent episodes of hypereosinophilia, and polyarthralgia suggested Churg–Strauss syndrome, which was excluded upon absence of eosinophilic vasculitis on any of the biopsies. However, corticosteroids were effective for hypereosinophilia. In addition to the hypereosinophilic syndrome a mitochondrial disorder with multi-system affection was diagnosed upon the clinical presentation and a muscle biopsy indicative of a mitochondrial disorder. Hypereosinophilia was interpreted as a manifestation of the mitochondrial disorder after exclusion of various differentials. Mitochondrial disease may go along with marked eosinophilia mimicking Churg–Strauss syndrome. Steroids may be useful to resolve episodic eosinophilia but may be ineffective for other features of mitochondrial disorders.