Expanding the phenotype of anauxetic dysplasia caused by biallelic NEPRO mutations: A case report

Abstract

The cartilage hair hypoplasia and anauxetic dysplasia (CHH-AD) spectrum encompasses a group of rare skeletal disorders, with anauxetic dysplasia (ANXD) at the most severe end of the spectrum. Biallelic variants in RMRP, POP1, and NEPRO (C3orf17) have previously been associated with the three currently recognized ANXD types. Generally, all types are characterized by severe short stature, brachydactyly, skin laxity, joint hypermobility and dislocations, and extensive skeletal abnormalities visible on radiological evaluation. Thus far, only five patients with type 3 anauxetic dysplasia (ANXD3) have been reported. Here, we describe one additional ANXD3 patient. We provide a detailed physical and radiological evaluation of this patient, in whom we identified a homozygous variant, c.280C > T, p.(Arg94Cys), in NEPRO. Our patient presented with clinically relevant features not previously described in ANXD3: atlantoaxial subluxation, extensive dental anomalies, and a sagittal suture craniosynostosis resulting in scaphocephaly. We provide an overview of the literature on ANXD3 and discuss our patient's characteristics in the context of previously described patients. This study expands the phenotypic spectrum of ANXD, particularly ANXD3. Greater awareness of the possibility of atlantoaxial subluxation, dental anomalies, and craniosynostosis may lead to more timely diagnosis and treatment.

Keywords: NEPRO; POP1; RMRP; anauxetic dysplasia; cartilage hair hypoplasia.