Chronic low back pain caused by metastatic adenocarcinoma of unknown origin in a young man: a case report

Introduction and importance: Low back pain (LBP) is one of the most common complaints and sacroiliac joint dysfunction is the third cause of this chronic burden. Sacroiliitis might be a primary sign of axial spondylarthritis, although it might be found in other diseases, and malignancies, either primary tumors or metastases, meanwhile, this is a rare case that is described as sacroiliitis with adenocarcinoma of unknown origin. Case presentation: A 24-year-old male presented at the hospital with fever and urinary retention. He had a history of progressively worsening chronic LBP, with increased curvature in the dorsal vertebrae. Physical examination revealed fever (39°C), a dorsal kyphosis with an absence of lumbar lordosis. Strength was low in the proximal and distal muscles of the lower limbs, with hyperreflexia in the left lower limb and paresthesia limbs in the whole lower and lower region of the abdomen. Laboratory studies revealed normocytic anemia, high ESR and CRP levels, and hypercalcemia with low PTH. The radiology study showed sacroiliitis, many lytic bone lesions, and a collapse in the 4th lumbar vertebral, and increased lung density. Biopsy from a lytic lesion showed metastatic poorly differentiated adenocarcinoma of unknown origin with features suggestive of pancreatic primary. Palliative radiotherapy was started; unfortunately, he died after 4 months. Clinical discussion: Cancer is an additional risk factor for the development of sacroiliac joint pain and disorder. A lot of tumors and metastases can be associated with sacroiliitis. Many patients present with bone lytic metastases of unknown origin as a first manifest. The association between metastatic adenocarcinoma and sacroiliitis was reported three cases in the literature; meanwhile, this was a rare case that described sacroiliitis with adenocarcinoma of unknown origin. Conclusion: Low back pain is one of the most common complaints, but it may be an initial symptom of serious conditions. Awareness of clinical clues can prevent faulty or delayed diagnoses. Although sacroiliitis is usually associated with axial spondylarthritis in adult patients, it can be the first manifestation of adenocarcinoma.