Bone Abstracts

Background: Osteogenesis imperfecta (OI) is characterized by bone fragility, resulting in low-energy fractures. Other features are compromised growth, blue sclerae, dental, cardiac and hearing abnormalities.

Presenting problem: A girl with OI, hypothyroidism and growth hormone (GH) deficiency is presented. She was born at 32 weeks [birth weight: 1890 gr, length: 44 cm]. Her mother had OI and thyroid nodules. Both were found with heterozygous mutation in the COL1A1 gene (c.2453dupG, pAla819fsX2). She presented at 5.7 yrs of age for growth failure and reported no fractures. She was on L-thyroxin due to primary hypothyroidism. On examination, her height was 99.7 cm (−2.9 SDS), weight: 15 kg (−2.25 SDS) and she had blue sclerae and hyperextensible joints. Baseline investigations [complete blood count, liver, renal and thyroid function and basic bone profile] were normal. IGF1 was low (88 ng/ml) and peak GH secretion was low at glucagon and clonidine stimulation tests (<10 ng/ml). Her bone age was delayed by two years and pituitary MRI was normal.

Clinical management: Replacement therapy with rhGH was started. She sustained a low-energy fracture at age 6.3 years and reported occasional, mild lumbar pain. A lateral spine Xray did not reveal vertebral fractures. Lumbar spine bone mineral density (BMD) was low for her age and sex, adjusted for height (Z-score=−3.2); so was the subcranial total body scan, with BMD Z-score=−2.6, at six months after initiation of therapy. After two years of rhGH treatment, her height was 117.8 cm (−2.2 SDS) and the follow up BMD Z-scores of the lumbar spine and total body scan were improved (−2 and −1.3, respectively).

Discussion: GH has a positive effect on bone growth and turnover by stimulating osteoblasts, collagen synthesis and longitudinal bone growth. Sillence et al. showed positive effects of GH on height, skeletal volume and BMD, and infer that it may be beneficial for these group of patients. Despite the lack of robust evidence for the use of GH in OI, our case illustrates the potential for skeletal improvement in OI patients with mild phenotype and confirmed GH deficiency and highlights the importance of investigating short stature in these patients thoroughly.

Disclosure: The authors declared no competing interests.