SAT-717 Patient With History of Noonan Syndrome and Pregnancy and Lactation Associated Osteoporosis

Abstract Disclosure: G. Gupta: None. M. Dillon: None. P. Pile: None. S. Rabieihashemi: None. I. Alpertunga: None. K. Newton: None. V. Kantorovich: None. Introduction: Pregnancy and lactation-associated osteoporosis (PLO) is rare, occurring in late pregnancy or lactation with low trauma or spontaneous fractures. Vertebral fractures are the most common fractures. Causes of PLO could be idiopathic, due to genetic predisposition, or secondary to underlying condition. Noonan syndrome (NS) is a disorder of RAS-mitogen activated protein kinase pathway which is linked to lower bone mass. We present a case of PLO in a patient with NS. Case: A 34-year-old breastfeeding female with NS (KRAS mutation), presented to the emergency room 6 weeks after delivery with sudden back pain after lifting her baby. Labs noted low magnesium 1 mg/dL, potassium 2.4 mmol/L, corrected calcium 7.8 mg/dL with PTH of 23 pg/mL (inappropriately normal), and 25 hydroxy vitamin D of 18 ng/mL. CT thoracic/lumbar spine and MRI showed T8, T12, L3 and L4 compression fractures. The patient started on calcium, magnesium and vitamin D supplementation. Nuclear bone scan showed increased uptake in 6th rib; PET/CT showed no evidence of malignancy. A new acute T11 compression fracture was noted despite bed rest. Bone density scan showed lumbar osteoporosis (Z score -3.8). She underwent kyphoplasty of T11. Bone turnover markers osteocalcin, n-telopeptide, and bone specific alkaline phosphatase were elevated. Breastfeeding stopped, and she was started on teriparatide. Sadly, she passed away a few months later due to electrolyte imbalances from underlying kidney disease. Discussion: PLO should be considered in pregnant or breastfeeding patients with new onset musculoskeletal pain or fracture. PLO occurs amid dynamic bone changes in pregnancy and lactation, where high calcium demand leads to maternal bone demineralization (more in pregnancy than in lactation) and recovery after weaning lactation. It is believed that those with PLO have underlying osteoblast defect leading to low bone formation. Our patient had back pain with vertebral compression fractures. She may have had low bone density at baseline, due to her KRAS mutation from NS which can affect bone mineralization. Lower bone density in NS is also due to muscle hypoplasia and insulin-growth factor 1 level. Fracture related pain is typical of PLO and warrants evaluation for risk factors and secondary causes. Conservative management such as stopping breastfeeding can suffice but, certain cases may need pharmacologic therapy. Emerging evidence favors teriparatide for PLO, showing greater bone density gain and better post-treatment bone mass retention with or without sequential antiresorptives compared to those with idiopathic osteoporosis. Presentation: Saturday, July 12, 2025