Unilateral Sacroiliac Hemiagenesis in a Young Woman Presenting With Chronic Mechanical Low Back and Buttock Pain: A Case Report

Sacral agenesis is a rare congenital malformation belonging to the spectrum of caudal regression syndrome, whose clinical manifestations are highly variable and depend on the phenotype of the disease.We report the case of a young woman who presented with chronic mechanical low back and buttock pain.Clinical examination revealed no significant abnormalities.Imaging studies, however, showed right-sided sacroiliac hemiagenesis associated with compensatory scoliosis.After surgical treatment was deemed unnecessary, the patient was managed conservatively with analgesics, muscle relaxants, and an individualized rehabilitation program.Her symptoms gradually improved, with a favorable clinical outcome.This case represents a mildly symptomatic form of sacral agenesis and emphasizes the important role of imaging in identifying these rare congenital abnormalities, which may otherwise remain unrecognized.