A 41-year-old G1P0 Caucasian lady presented with atraumatic polyarticular pain on a background of obesity and likely polycystic ovarian syndrome. She developed left knee pain at 17 weeks gestation followed by severe right knee and bilateral hip pain at 28 weeks. She was unable to weight bear due to pain. Later, she developed gestational diabetes mellitus.
Based on the MRI findings of the hips and knees which showed bony oedematous changes, a diagnosis of transient osteoporosis of pregnancy (TOP) was made. Postpartum BMD showing lumbar spine Z score of -1.9 (T score -1.8) and femoral neck Z score of -3.6 (T score -3.9) and fractures at T7 and T8 on x-ray confirmed the diagnosis. Secondary osteoporosis screen was unremarkable.
At 38 weeks, the patient had an uncomplicated elective caesarian section. The patient returned to full weight bearing over the following 6 months. At six months post partum, there was resolution of the bony oedematous changes on MRI. At seven months, lumbar Z score improved to -1.7 (T score -1.5) and left hip Z score to -2.3 (T score -2.6).
Transient Osteoporosis of Pregnancy (TOP) is a rare condition that typically presents in the third trimester of pregnancy with severe hip pain on weight bearing, sometimes with fracture. 1 There is only one prior case report of polyarticular TOP. 2 Symptoms and imaging changes resolve without intervention within weeks to months postpartum. 3
Our TOP case is unique because of simultaneous multiple sites of involvement.
Differential diagnosis includes transient migrating osteoporosis of pregnancy. 4 Other conditions including avascular necrosis, infection, and non-osteoporotic stress fractures were ruled out. 1 It is unclear if genetic causes (e.g. LRP5 mutation) should be searched for. 5 Aetiology of TOP is unclear. Treatment is conservative and involves rest, vitamin D and calcium replacement. 1