We present a 73-year-old man with isolated adrenocorticotropic hormone deficiency and "flexion contractures" syndrome along with a review of the relevant literature. The patient initially presented anorexia, vomiting, arthralgias, malaise, and weight loss, which progressively deteriorated during the subsequent 6 months. He was admitted to the hospital with fever, confusion, severe cachexia, sinus tachycardia, low blood pressure, hyponatremia, and inability to stand or walk due to severe flexion contractures of the lower extremities (from hips to knees). The flexion contractures were not resolved by physiotherapy or diazepam administration. Due to his life-threatening condition the patient was empirically submitted to glucocorticoid replacement therapy and a remarkable relief from all the above symptoms was observed. A subsequent thorough endocrine investigation suggested the diagnosis of isolated ACTH deficiency (IAD) of unknown pathogenetic mechanism. Hence, in patients with "flexion contractures" syndrome, the pituitary adrenal axis should be evaluated.