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Pathologic Diagnosis of Achondrogenesis Type 2 in a Fragmented Fetus: Case Report and Evidence-Based Differential Diagnostic Approach in the Early Midtrimester

“…This pattern is suggestive of Blomstrand dysplasia. Classically, Blomstrand dysplasia is described as exhibiting marked generalized osteosclerosis (increased bone density/ossification) with very short long bones showing barbell-like metaphyses and thickened ribs [25]. Early midtrimester reports of Blomstrand dysplasia (12 weeks via D&E, 19.5 weeks) demonstrate that the classic above-mentioned findings are already developed at this early gestational age [26].…”

“…Osteogenesis imperfecta type 2a is one of the most common lethal GSDs [29,30] and exhibits true fractures. In contrast, Greenberg dysplasia is a very rare disorder and exhibits pseudofractures due to the presence of abnormal calcifications [25].…”

“…Classic radiologic findings for this group include extremely short long bones with true fractures in the long bones and ribs with deficient ossification of the calvarium [9,10]. The long bone fractures typically are described as appearing “crumpled” or “accordion-like” versus the stippled/moth eaten look of the pseudofractures seen in Greenberg dysplasia (see below) [25]. Two reports of fetuses with osteogenesis imperfecta type 2a diagnosed at 17 and 18 weeks gestation, respectively, both showed the characteristic long bone and rib fractures, as well as deficient ossification of the calvarium [31,32].…”

“…Classic radiologic findings for Greenberg dysplasia include marked punctate calcifications (also referred to as stippling, a moth-eaten appearance, or pseudofractures) of the long bones and ribs (among other bones) and severe shortening of the long bones. Poor skull ossification is also seen [25]. Case reports of midtrimester fetuses with Greenberg dysplasia reveal that the characteristic findings are easily identifiable by 15 and 17 weeks gestation [33,34].…”

“…Of note, the entity known as “boomerang dysplasia” is included under the same category as atelosteogenesis type 1 in the current classification system [1]. Although both entities are due to the same genetic mutation ( filamin B) , boomerang dysplasia generally exhibits more severe radiologic abnormalities [3,10,25]. They will be considered together here.…”