This is a case report on a young patient with severe osteoporosis that was initially revealed when she presented with polyarthralgia during her second pregnancy. Postpartum, the pain increased and her X-ray did not show any abnormalities. A bone scintigraphy was performed. It indicated an inflammatory rheumatic disorder. Six months after partum, an investigation of right coxalgia revealed a spontaneous basicervical fracture. Given the persistent polyarthralgia, the patient underwent a new scintigraphy, which revealed areas of what looked to be old rib and L1 fractures. A subsequent full body magnetic resonance imaging (MRI) scan revealed signal abnormalities that could indicate multiple lower limb bone fractures. Despite exhaustive biological, radiological, and histological testing, no secondary cause for the osteoporosis was found. The patient was started on teriparatide. We finally concluded that, despite the atypical presentation, the patient was suffering from postpregnancy osteoporosis. It is possible that the frequency of occurrence of this still poorly understood disease is underestimated.