[Isolated ACTH deficiency clinically presented as stiff-person syndrome, successfully treated by hormonal replacement: a case report].

A 65-year-old man was admitted to our hospital with a 6-year history of painful muscle stiffness in his trunk and lower limbs, preventing him from walking. Stiff-person syndrome (SPS) was diagnosed because the patient had symptoms of painful muscle spasms elicited by tactile stimulation without joint contracture. Although SPS- related autoantibodies in the serum, including anti-glycine R, anti-amphiphysin, anti-glutamic acid decarboxylase (GAD), anti-dipeptidyl peptidase-like protein (DPPX) and anti-γ-aminobutyric acid-A (GABA _A ) R, were negative, the ACTH and cortisol levels were low. On the basis of additional loading tests for anterior pituitary function and ACTH, isolated ACTH deficiency (IAD) was diagnosed. Hormonal replacement therapy with hydrocortisone at 15 mg/day ameliorated the condition quickly, and the patient became asymptomatic after three months. Flexion contractures have been reported as musculoskeletal symptoms of IAD, but are not usually evident in patients with SPS. The present case illustrates that the painful muscle spasms elicited by tactile stimulation without joint contracture characteristic of SPS can also be symptoms of IAD.