Lung Transplantation in a Patient With Osteogenesis Imperfecta and Osteoporosis

Background: Osteogenesis imperfecta (OI) and transplantation (TP) are independently associated with fractures. Yet reports regarding the skeletal effects of organ TP in OI are limited. We report the early skeletal outcomes in an OI patient with osteoporosis who underwent lung TP. Clinical Case: A 35-year-old man with moderate/severe OI and severe bronchiectasis was admitted for progressive respiratory failure and expedited lung TP evaluation. OI was diagnosed at age 10 after sustaining a hairline coccyx fracture when falling off a stool; scoliosis was diagnosed at age 14; additional fractures included ankle (18 y), toes (28 y) and rib (34 y). He had dentogenesis imperfecta, but no hearing loss, easy bruising or OI family history. Bronchiectasis also began at age 10 and progressed, with multiple drug resistant infections and glucocorticoid (GC) treatments. At admission, he was on 6L oxygen and bed-bound from dyspnea. Notably, he had been rejected twice for TP because of his bone disease. Admission medications included calcium, D3, famotidine, inhaled fluticasone, tobramycin, and tiotropium bromide. His exam was notable for height 5’5”, BMI 16.5 kg/m2, kyphoscoliosis, blue sclera and joint laxity. Labs were notable for (mg/dl): serum calcium 9.4, magnesium 2.4, phosphate 4.4; albumin 4.2 g/dl, alkaline phosphatase 75 U/L, 25(OH)D 34 ng/ml, sCTX 535 pg/ml, urinary calcium 370 mg/24 hr. DXA showed T-scores of -4.7 (lumbar spine), -3.3 (femoral neck), -3.2 (total hip), -2.6 (1/3 radius). Endocrinology was consulted about the skeletal risk of lung transplantation. Discussion and Follow-up:The patient’s manifestations of OI increased the risk of adverse skeletal outcomes. His high CTX suggested increased bone resorption, often seen with OI; bone formation was not directly measured but in OI is frequently reduced. Notably, his bronchiectasis was likely related to the OI: in addition to restrictive lung disease in OI, the abnormal type 1 collagen likely alters alveolar structure and elasticity. His risk for post-TP fractures was high given that the expected post-TP bone loss would likely be exacerbated by high dose GCs further increasing bone resorption and reducing presumed low bone formation. Nevertheless, because he had never sustained a major fracture even without OI treatment, the decision was made to proceed. He received zoledronate (ZOL) 5 mg IV and underwent an uncomplicated double lung transplant; initial high dose GCs were tapered to prednisone 10 mg/d. Three months later, he has steadily rising lung function, excellent functional status, and is working full time. A current sCTX of 73 pg/ml suggests that bone loss is not increased. Admittedly, the patient remains within the early high-risk fracture window. Yet this case is the first report to our knowledge which suggests that lung TP in an OI patient treated with ZOL did not lead to fracture in the early post-TP period.