We report the case of a 48-year-old male, whose musculoskeletal manifestations, previously related to long-term renal replacement therapy (RRT), were diagnosed as ankylosing spondylitis when symptoms changed their pattern on daily hemodialysis (DHD). The patient started RRT in 1981; in 1985 he received a cadaver graft, which failed in 1987. Secondary hyperparathyroidism, amyloid geoids, bilateral carpal tunnel syndrome and high aluminium levels were present. Musculoskeletal pain, reported since 1986, involved feet, heels, hips, shoulders, hands, spine. Symptoms impairing daily life did not improve after parathyroidectomy. He developed chronic hypotension and recurrent atrial fibrillation. In 1994 and 1998, because of thoracic pain, coronarography was performed (normal on both occasions). In June 2000, DHD was started. Equivalent renal clearance increased from 9-12 to 15-17 mL/min. Well-being remarkably improved. In September 2000, musculoskeletal pain worsened and bilateral Achilles tendinitis occurred. The worsening of musculoskeletal symptoms despite the improvements in well-being and other dialysis related symptoms prompted a re-evaluation of the case. The diagnosis of ankylosing spondylitis was based on: history of plantar fasciitis, bilateral Achilles tendinitis, inflammatory spinal pain with limitation of lumbar spine mobility (positive Schober test), radiological evidence of grade 2 bilateral sacroiliitis, presence of HLA-B27. This diagnosis cast light on the episodes of chest pain, explained by enthesopathy at the costosternal and manubriosternal joints and atrial fibrillation, due to HLA-B27 associated impairment in heart conduction. This case exemplifies the difficulty of differential diagnosis of multisystem illness in patients with long RRT follow-up.