A Case of Cleidocranial Dysplasia with a Novel Mutation and Growth Velocity Gain with Growth Hormone Treatment

A Case Series of Three Patients with Cleidocranial Dysplasia: Clinical Presentation and Diagnostic Considerations

Cleidocranial dysplasia (CCD) is a rare genetic condition that affects the bones and teeth. In our study, we presented three cases of CCD, including one with a new mutation and two with a family history. Case 1 had a unique heterozygous frameshift mutation (NM_001015051,c.762del, p.(Ser256Valfs*2)), while Case 2 and her brother (Case 3) had a common pathogenic missense mutation (NM_001015051,c.674G, p.Arg225Gln), which was also found in their father. The mutation in Case 1 was not reported before. Interestingly, the symptoms in Case 1, with the new mutation, were less severe than the other cases and the previous reports.

Novel Loss-of-Function Mutations in NPR2 Cause Acromesomelic Dysplasia, Maroteaux Type

Acromesomelic dysplasia, Maroteaux type (AMDM) is a rare skeletal dysplasia characterized by severe disproportionate short stature, short hands and feet, normal intelligence, and facial dysmorphism. Homozygous or compound heterozygous mutations in the natriuretic peptide receptor 2 (NPR2) gene produce growth-restricted phenotypes. The current study was designed to identify and characterize NPR2 loss-of-function mutations in patients with AMDM and to explore therapeutic responses to recombinant growth hormone (rhGH). NPR2 was sequenced in two Chinese patients with AMDM via next generation sequencing, and in silico structural analysis or transcript analysis of two novel variants was performed to examine putative protein changes. rhGH treatment was started for patient 1. Three NPR2 mutations were identified in two unrelated cases: two compound heterozygous mutations c.1112G>A p.(Arg371Gln) and c.2887+2T>C in patient 1 and a homozygous mutation c.329G>A p.(Arg110His) in patient 2, yielding distinct phenotypes. RNA extracted from peripheral blood cells of patient 1 showed alternatively spliced transcripts not present in control cells. Homology modeling analyses suggested that the c.1112G>A p.(Arg371Gln) mutation disrupted the binding of NPR-B homodimer to its ligand (C-type natriuretic peptide) in the extracellular domain as a result of global allosteric effects on homodimer formation. Thus, c.2887+2T>C and c.1112G>A p.(Arg371Gln) in NPR2 were loss-of-function mutations. Furthermore, rhGH therapy in patient 1 increased the patient’s height by 0.6SDS over 15 months without adversely affecting the trunk-leg proportion. The short-term growth-promoting effect was equivalent to that reported for idiopathic short stature. Overall, our findings broadened the genotypic spectrum of NPR2 mutations in individuals with AMDM and provided insights into the efficacy of rhGH in these patients.

Skeletal and molecular findings in 51 Cleidocranial dysplasia patients from Turkey

Loss or decrease of function in runt-related transcription factor 2 encoded by RUNX2 is known to cause a rare autosomal-dominant skeletal disorder, cleidocranial dysplasia (CCD). Clinical spectrum and genetic findings in 51 CCD patients from 30 unrelated families are herein presented. In a majority of the patients, facial abnormalities, such as delayed fontanel closure (89%), parietal and frontal bossing (80%), metopic groove (77%), midface hypoplasia (94%), and abnormal mobility of shoulders (90%), were recorded following clinical examination. In approximately one-half of the subjects, wormian bone (51%), short stature (43%), bell-shaped thorax (42%), wide pubic symphysis (50%), hypoplastic iliac wing (59%), and chef's hat sign (44%) presented in available radiological examinations. Scoliosis was identified in 28% of the patients. Investigation of RUNX2 revealed small sequence alterations in 90% and gross deletions in 10% of the patients; collectively, 23 variants including 11 novel changes (c.29_30insT, c.203delAinsCG, c.423 + 2delT, c.443_454delTACCAGATGGGAinsG, c.505C > T, c.594_595delCTinsG, c.636_637insC, c.685 + 5G > A, c.1088G > T, c.1281delC, Exon 6-9 deletion) presented high allelic heterogeneity. Novel c.29_30insT is unique in affecting the P1-driven long isoform of RUNX2, which is expected to disrupt the N-terminal region of RUNX2; this was shown in two unrelated phenotypically discordant patients. The clinical findings highlighted mild intra-familial genotype-phenotype correlation in our CCD cohort.

Cleidocranial dysplasia

We present a 4-year-old girl with persistent anterior fontanelle and narrow sloping shoulders. The X-ray imaging revealed widely open anterior fontanelle, supernumerary teeth, and absence of clavicles. Therefore, the diagnosis was cleidocranial dysplasia, which is a rare autosomal dominant skeletal disease, caused by the mutation in the gene on 6p21 encoding transcription factor CBFA1 (runt-related transcription factor 2-RUNX2). The girl remains under close surveilance, her anterior fontanelle closed spontaneously at the age of 9 years.

Cleidocranial dysplasia with growth hormone deficiency: a case report

Background

Cleidocranial dysplasia (CCD) is a rare skeletal disorder with autosomal dominant inheritance that is characterized by hypoplastic clavicles, delayed closure of the cranial sutures, dental abnormalities, and short stature, among other features. The responsible gene for CCD is RUNX2 located on the short arm of chromosome 6p21. In general, there are intrafamilial variations in height among CCD patients. Few studies have reported data on recombinant human growth hormone (rhGH) treatment for patients with CCD; thus, it remains to be elucidated whether rhGH treatment can improve short stature. Here, we report a case of a 6-year-old girl with CCD who has growth hormone deficiency (GHD) and a novel mutation of RUNX2.

Case presentation

At 5 years of age, this patient was diagnosed with GHD and rhGH treatment was initiated. Thereafter, she was diagnosed with CCD due to the presence of hypoplastic clavicles and an open fontanelle, which was also observed in her mother and brother. She responded well to rhGH treatment; her height improved from − 3.2 SD to − 2.4 SD after 13 months.

Conclusion

A detailed patient history and physical examination are necessary for the early diagnosis of CCD. Similarly, to ascertain the effect of rhGH treatment, careful evaluation of the patient’s final height post-therapy is needed.

Identification of RUNX2 variants associated with cleidocranial dysplasia

Background

Cleidocranial dysplasia (CCD) is a rare autosomal dominant disorder mainly characterized by hypoplastic or absent clavicles, delayed closure of the fontanelles, multiple dental abnormalities, and short stature. Runt-related transcription factor 2 (RUNX2) gene variants can cause CCD, but are not identified in all CCD patients.

Methods

In this study, we detected genetic variants in seven unrelated children with CCD by targeted high-throughput DNA sequencing or Sanger sequencing.

Results

All patients carried a RUNX2 variant, totally including three novel pathogenic variants (c.722_725delTGTT, p.Leu241Serfs*8; c.231_232delTG, Ala78Glyfs*82; c.909C > G, p.Tyr303*), three reported pathogenic variants (c.577C > T, p.Arg193*; c.574G > A, p.Gly192Arg; c.673 C > T, p.Arg225Trp), one likely pathogenic variant (c.668G > T, p.Gly223Val). The analysis of the variant source showed that all variants were de novo except the two variants (c.909C > G, p.Tyr303*; c.668G > T, p.Gly223Val) inherited from the patient’s father and mother with CCD respectively. Further bioinformatics analysis indicated that these variants could influence the structure of RUNX2 protein by changing the number of H-bonds or amino acids. The experimental result showed that the Gly223Val mutation made RUNX2 protein unable to quantitatively accumulate in the nucleus.

Conclusions

The present study expands the pathogenic variant spectrum of RUNX2 gene, which will contribute to the diagnosis of CCD and better genetic counseling in the future.