Proximal muscle weakness as the sole manifestation of Cushing’s disease, misdiagnosed as dermatomyositis: a case report

BACKGROUND: Cushing’s syndrome consists of signs and symptoms related to prolonged exposure to high levels of glucocorticoid, and should be considered in individuals with the discriminatory signs and symptoms. Proximal myopathy is an important discriminatory sign. CASE PRESENTATION: We report the case of a 36-year-old Iranian man who presented with proximal muscle weakness. He visited a rheumatologist in an outpatient clinic, and according to proximal muscle weakness and heliotrope rash (based on the rheumatologist’s notes) with the impression of dermatomyositis, prednisolone and azathioprine were prescribed for him that did not improve his clinical status and he was gradually wheelchair dependent. He was admitted to the hospital for evaluation of paraneoplastic syndromes. Standard laboratory tests and imaging were unremarkable, other than a brain magnetic resonance imaging that demonstrated a 30 × 12 mm homogeneously enhancing mass in the sellar region with extension to the suprasellar area. He had serum cortisol of 295 ng/mL, and adrenocorticotropic hormone of 222 pg/mL (on 5 mg prednisolone twice daily), with a diagnosis of Cushing’s disease. He underwent two sessions of trans-sphenoidal surgery 4 months apart. After the first surgery, the proximal muscle weakness improved dramatically and he was walking with the aid of a walker, and after the second surgery he is walking without any aids. CONCLUSION: This case report emphasizes the high diagnostic importance of proximal muscle weakness as the sole presenting manifestation of Cushing’s syndrome/disease.