Pseudotumor Deltoideus Associated With Persistent Focal Mid-Arm Pain: A Case Report

Abstract

Background:
Pseudotumor deltoideus is a benign cortical change at the site where the deltoid muscle inserts on the humerus. It is often found by chance. On a plain radiograph, however, it can look like infection or a bone tumour. Reports of patients whose pain continues at the exact site of the lesion are few.
Case presentation:
A 44-year-old woman had localised pain in the right mid-arm for about three years. Analgesics did not relieve it. She reported no trauma, overhead activity, strenuous exercise or occupational overuse. Examination showed a well-defined area of tenderness over the mid-arm, at the site of the radiographic abnormality. Shoulder movement was full, and resisted abduction reproduced the pain.
There was no swelling, palpable mass or neurological symptom. Radiographs of the right humerus showed focal cortical irregularity and thickening at the deltoid insertion. MRI of the arm showed focal cortical and periosteal thickening. There was no aggressive marrow abnormality, soft-tissue mass or collection. Shoulder MRI showed mild supraspinatus tendinosis, acromioclavicular
degenerative change and features of mild adhesive capsulitis. These findings were considered unlikely to explain the isolated mid-arm tenderness. She was treated with analgesics and gabapentin. Biopsy and surgery were not undertaken because the imaging was considered typical and showed no aggressive features. After three months the pain had improved only slightly, and the focal tenderness
remained.
Conclusion:
Pseudotumor deltoideus can be diagnosed from its site and its radiographic and MRI appearance. When pain and tenderness persist at the same site, the patient needs clinical follow-up. Biopsy may be avoided when the clinical and imaging findings are characteristic and show no suspicious features.