Antenatal ultrasound diagnosis of osteogenesis imperfecta type II/III with rocker bottom foot, rib beading and preserved calvarial ossification: a case report

Abstract

Osteogenesis imperfecta (OI), is a rare genetic disorder, primarily characterized by skeletal fragility, recurrent fractures, and bone deformities due to mutational defects in collagen synthesis and subsequent bone matrix. In routine, prenatal mid trimester anomaly scan can facilitate an early diagnosis of such skeletal dysplasias. We present a rare case of prenatal OI identified at 23 weeks of gestation in a 28-year-old female during a mid-trimester screening which demonstrated multiple atypical sonographic findings. There were multiple fractures, bowing of long bones and rhizomelic proximal segments suggesting OI, mostly consistent with type II/III OI. Of particular significance, striking unusual findings such as Rocker-bottom foot, beaded ribs, disproportionate limbs, and ossification with firm calvarium were noticed. The thoracic cavity however had no relevant inordinate ratios. These overlapping findings with other osteochondral disorders posed a diagnostic challenge and hampered distinction in OI subtypes. This case highlights the significance of early recognition of both classic and atypical ultrasound evaluation of OI in accurate antepartum analysis and subsequent post birth management alongside relevant counseling. The aim is to offer clinical awareness and refined diagnostic criteria for OI by suggesting an expanded phenotypic spectrum beyond conventional patterns for facilitation in terms of early recognition and directed clinical approach.