Bone Abstracts

Background: The baby growing in its mother’s womb needs calcium for skeletal development. Maternal osteoporosis has been attributed to pregnancy in some cases.

Presenting problem: A 27-year-old woman in the 7th month of her first pregnancy complained of mid-thoracic back pain after lifting a non-heavy object. The pain remained with differing intensity and was attributed to her pregnancy. After the delivery of a healthy child, the back pain prevented her from lifting her baby. Physical therapy had no effect. Her past medical history was uneventful without fractures, except for severely reduced vision of her left eye since birth. She used three dairy products daily and no medication. Family history revealed that her maternal grandmother had osteoporosis at old age. Physical examination: height 1.58 m, weight: 53 kg. No blue sclerae; amblyopic left eye. No hyperlaxity of skin or joints. Laboratory examination including serum calcium, phosphate, alkaline phosphatase, creatinine, bCTX 25-hydroxyvitamin D and TSH was normal. Spinal X-ray showed end-plate compressions of thoracic vertebrae (Th7, 9, 10 and 12). DXA-scanning showed severe osteoporosis (T-score L2-L4: −5.7 S.D., femur neck: −3.9 S.D.). DNA analyses revealed two mutations in the LRP5 gene. Family screening with DXA and DNA analyses was performed. Her mother, recently postmenopausal, had osteoporosis and carried the LRP5 mutation. Her only brother, treated with cabergoline for a microprolactinoma, had osteopenia on DXA and was an LRP5 mutation carrier.

Clinical management: The patient was diagnosed with osteoporosis pseudoglioma syndrome and treated with risedronate for 2.5 years. BMD and back pain improved. She stopped the use of bisphosponate 6 months before planning a second pregnancy.

Discussion: Potentially underlying genetic causes like osteogenesis imperfecta or osteoporosis pseudoglioma syndrome should be excluded in pregnancy-associated osteoporosis. A genetic diagnosis has implications for the patient and relatives. More studies regarding bisphosphonate treatment preceding conception are desirable.