Bone Abstracts

Background: Mutations in SATB2 have been described in association with a unique phenotype known as SATB2-associated syndrome (SAS). This condition is characterised by severe intellectual disability affecting speech development, behaviour, facial features and dental anomalies. Skeletal features and osteoporosis have been reported in older individuals (aged 15–36), in association with point mutations. We report a 24-year-old man with a SATB2 missense mutation and classical SAS phenotype, with osteoporosis, fractures and tibial bowing from early childhood.

Presenting problem: The patient developed anterior bowing of the tibiae at 4 years of age. He had 17 fractures, the first at six years of age. Osteoporosis was diagnosed on DEXA scan at age 9.

Clinical management: He was treated with intravenous bisphosphonates for 10 years. Radiological examination aged 12 showed lateral bowing of both femora and anterior bowing of the tibulae and fibulae, in association with diaphyseal widening and cortical thickening. DEXA showed normal bone density 6 months after stopping bisphosphonate therapy. Bone chemistry, including ALP level, is normal. He has severe intellectual disability. He has also required treatment for multiple dental abscesses, with abnormal tooth architecture. Exome sequencing identified a de novo heterozygous missense mutation in exon 6 of SATB2 (c.1169 C>T, p.Thr390Ile), confirmed by Sanger sequencing.

Discussion: This case provides further evidence for the association between SAT2B mutation, osteoporosis and tibial bowing, presenting younger in this patient than previously reported. In patients with intellectual disability of unknown cause, the presence of these distinctive skeletal features may aid clinical diagnosis of SAS. The optimal bone density surveillance and treatment strategy remains to be determined for patients diagnosed with SAS.

Disclosure: The authors declared no competing interests.