Heterozygous pathogenic variants involving CBFB cause a new skeletal disorder resembling cleidocranial dysplasia.

BACKGROUND: Cleidocranial dysplasia (CCD) is a rare skeletal dysplasia with significant clinical variability. Patients with CCD typically present with delayed closure of fontanels and cranial sutures, dental anomalies, clavicular hypoplasia or aplasia and short stature. Runt-related transcription factor 2 (RUNX2) is currently the only known disease-causing gene for CCD, but several studies have suggested locus heterogeneity. METHODS: The cohort consists of eight subjects from five unrelated families partially identified through GeneMatcher. Exome or genome sequencing was applied and in two subjects the effect of the variant was investigated at RNA level. RESULTS: In each subject a heterozygous pathogenic variant in CBFB was detected, whereas no genomic alteration involving RUNX2 was found. Three CBFB variants (one splice site alteration, one nonsense variant, one 2 bp duplication) were shown to result in a premature stop codon. A large intragenic deletion was found to delete exon 4, without affecting CBFB expression. The effect of a second splice site variant could not be determined but most likely results in a shortened or absent protein. Affected individuals showed similarities with RUNX2-related CCD, including dental and clavicular abnormalities. Normal stature and neurocognitive problems were however distinguishing features. CBFB encodes the core-binding factor ß subunit, which can interact with all RUNX proteins (RUNX1, RUNX2, RUNX3) to form heterodimeric transcription factors. This may explain the phenotypic differences between CBFB-related and RUNX2-related CCD. CONCLUSION: We confirm the previously suggested locus heterogeneity for CCD by identifying five pathogenic variants in CBFB in a cohort of eight individuals with clinical and radiographic features reminiscent of CCD.

Nosology of genetic skeletal disorders: 2023 revision.

The "Nosology of genetic skeletal disorders" has undergone its 11th revision and now contains 771 entries associated with 552 genes reflecting advances in molecular delineation of new disorders thanks to advances in DNA sequencing technology. The most significant change as compared to previous versions is the adoption of the dyadic naming system, systematically associating a phenotypic entity with the gene it arises from. We consider this a significant step forward as dyadic naming is more informative and less prone to errors than the traditional use of list numberings and eponyms. Despite the adoption of dyadic naming, efforts have been made to maintain strong ties to the MIM catalog and its historical data. As with the previous versions, the list of disorders and genes in the Nosology may be useful in considering the differential diagnosis in the clinic, directing bioinformatic analysis of next-generation sequencing results, and providing a basis for novel advances in biology and medicine.

A homozygous hypomorphic BNIP1 variant causes an increase in autophagosomes and reduced autophagic flux and results in a spondylo-epiphyseal dysplasia.

BNIP1 (BCL2 interacting protein 1) is a soluble N-ethylmaleimide-sensitive factor-attachment protein receptor involved in ER membrane fusion. We identified the homozygous BNIP1 intronic variant c.84+3A>T in the apparently unrelated patients 1 and 2 with disproportionate short stature. Radiographs showed abnormalities affecting both the axial and appendicular skeleton and spondylo-epiphyseal dysplasia. We detected ~80% aberrantly spliced BNIP1 pre-mRNAs, reduced BNIP1 mRNA level to ~80%, and BNIP1 protein level reduction by ~50% in patient 1 compared to control fibroblasts. The BNIP1 ortholog in Drosophila, Sec20, regulates autophagy and lysosomal degradation. We assessed lysosome positioning and identified a decrease in lysosomes in the perinuclear region and an increase in the cell periphery in patient 1 cells. Immunofluorescence microscopy and immunoblotting demonstrated an increase in LC3B-positive structures and LC3B-II levels, respectively, in patient 1 fibroblasts under steady-state condition. Treatment of serum-starved fibroblasts with or without bafilomycin A1 identified significantly decreased autophagic flux in patient 1 cells. Our data suggest a block at the terminal stage of autolysosome formation and/or clearance in patient fibroblasts. BNIP1 together with RAB33B and VPS16, disease genes for Smith-McCort dysplasia 2 and a multisystem disorder with short stature, respectively, highlight the importance of autophagy in skeletal development.

Bi-allelic Loss-of-Function Mutations in the NPR-C Receptor Result in Enhanced Growth and Connective Tissue Abnormalities.

The natriuretic peptide signaling pathway has been implicated in many cellular processes, including endochondral ossification and bone growth. More precisely, different mutations in the NPR-B receptor and the CNP ligand have been identified in individuals with either short or tall stature. In this study we show that the NPR-C receptor (encoded by NPR3) is also important for the regulation of linear bone growth. We report four individuals, originating from three different families, with a phenotype characterized by tall stature, long digits, and extra epiphyses in the hands and feet. In addition, aortic dilatation was observed in two of these families. In each affected individual, we identified a bi-allelic loss-of-function mutation in NPR3. The missense mutations (c.442T>C [p.Ser148Pro] and c.1088A>T [p.Asp363Val]) resulted in intracellular retention of the NPR-C receptor and absent localization on the plasma membrane, whereas the nonsense mutation (c.1524delC [p.Tyr508∗]) resulted in nonsense-mediated mRNA decay. Biochemical analysis of plasma from two affected and unrelated individuals revealed a reduced NTproNP/NP ratio for all ligands and also high cGMP levels. These data strongly suggest a reduced clearance of natriuretic peptides by the defective NPR-C receptor and consequently increased activity of the NPR-A/B receptors. In conclusion, this study demonstrates that loss-of-function mutations in NPR3 result in increased NPR-A/B signaling activity and cause a phenotype marked by enhanced bone growth and cardiovascular abnormalities.

Biallelic variants p.Arg1133Cys and p.Arg1379Cys in COL2A1: Further delineation of phenotypic spectrum of recessive Type 2 collagenopathies.

The phenotypic spectrum of Type 2 collagenopathies ranges from lethal achondrogenesis Type 2 to milder osteoarthritis with mild chondrodysplasia. All of them are monoallelic except for the two recent reports showing that biallelic variants in COL2A1 can cause spondyloepiphyseal dysplasia congenita in two children. Here we report two additional families with homozygous variants, c.4135C>T (p.Arg1379Cys) and c.3190C>T (p.Arg1133Cys) in COL2A1 resulting in two distinct skeletal dysplasia phenotypes of intermediate severity. Though all six patients from four families exhibit a spondylo-epimetaphyseal dysplasia, they demonstrate a wide variation in severity of short stature and involvement of epiphyses, metaphyses, and vertebrae. We hypothesize that the variants are likely to be hypomorphic, given the underlying mechanisms of disease causation for known heterozygous variants in COL2A1. With this report, we provide further evidence to the existence of autosomal recessive Type 2 collagenopathy.

Fibrous Dysplasia, Paget's Disease of Bone, and Other Uncommon Sclerotic Bone Lesions of the Craniofacial Bones.

Imaging studies of the brain, head and neck, sinuses, and dental computed tomography are among the most frequently performed procedures in radiologic departments. Systematic evaluation in the bone window may reveal common and uncommon sclerotic osseous abnormalities of the craniofacial skeleton.Most of these findings are incidental and unrelated to the initial clinical indications. Sporadically symptoms may arise due to lesional mass effect with compression on adjacent structures and neuroforaminal encroachment, resulting in proptosis, vision, or hearing loss. Other symptoms include craniofacial deformity, mandibular occlusion deformity, and local pain.This article reviews the most common disorders characterized by an increased bone density involving the craniofacial bones including fibrous dysplasia, Paget's disease of bone, meningioma with associated hyperostosis, and osteoma. Finally, typical examples of rarer sclerosing bone dysplasias are discussed as well.Emphasis is placed on imaging features and the differential diagnosis.

Nosology and classification of genetic skeletal disorders: 2019 revision.

The application of massively parallel sequencing technology to the field of skeletal disorders has boosted the discovery of the underlying genetic defect for many of these diseases. It has also resulted in the delineation of new clinical entities and the identification of genes and pathways that had not previously been associated with skeletal disorders. These rapid advances have prompted the Nosology Committee of the International Skeletal Dysplasia Society to revise and update the last (2015) version of the Nosology and Classification of Genetic Skeletal Disorders. This newest and tenth version of the Nosology comprises 461 different diseases that are classified into 42 groups based on their clinical, radiographic, and/or molecular phenotypes. Remarkably, pathogenic variants affecting 437 different genes have been found in 425/461 (92%) of these disorders. By providing a reference list of recognized entities and their causal genes, the Nosology should help clinicians achieve accurate diagnoses for their patients and help scientists advance research in skeletal biology.

HDAC8 mutations in Cornelia de Lange syndrome affect the cohesin acetylation cycle.

Cornelia de Lange syndrome (CdLS) is a dominantly inherited congenital malformation disorder, caused by mutations in the cohesin-loading protein NIPBL for nearly 60% of individuals with classical CdLS, and by mutations in the core cohesin components SMC1A (~5%) and SMC3 (<1%) for a smaller fraction of probands. In humans, the multisubunit complex cohesin is made up of SMC1, SMC3, RAD21 and a STAG protein. These form a ring structure that is proposed to encircle sister chromatids to mediate sister chromatid cohesion and also has key roles in gene regulation. SMC3 is acetylated during S-phase to establish cohesiveness of chromatin-loaded cohesin, and in yeast, the class I histone deacetylase Hos1 deacetylates SMC3 during anaphase. Here we identify HDAC8 as the vertebrate SMC3 deacetylase, as well as loss-of-function HDAC8 mutations in six CdLS probands. Loss of HDAC8 activity results in increased SMC3 acetylation and inefficient dissolution of the 'used' cohesin complex released from chromatin in both prophase and anaphase. SMC3 with retained acetylation is loaded onto chromatin, and chromatin immunoprecipitation sequencing analysis demonstrates decreased occupancy of cohesin localization sites that results in a consistent pattern of altered transcription seen in CdLS cell lines with either NIPBL or HDAC8 mutations.

Loss-of-function HDAC8 mutations cause a phenotypic spectrum of Cornelia de Lange syndrome-like features, ocular hypertelorism, large fontanelle and X-linked inheritance.

Cornelia de Lange syndrome (CdLS) is a multisystem genetic disorder with distinct facies, growth failure, intellectual disability, distal limb anomalies, gastrointestinal and neurological disease. Mutations in NIPBL, encoding a cohesin regulatory protein, account for >80% of cases with typical facies. Mutations in the core cohesin complex proteins, encoded by the SMC1A, SMC3 and RAD21 genes, together account for ∼5% of subjects, often with atypical CdLS features. Recently, we identified mutations in the X-linked gene HDAC8 as the cause of a small number of CdLS cases. Here, we report a cohort of 38 individuals with an emerging spectrum of features caused by HDAC8 mutations. For several individuals, the diagnosis of CdLS was not considered prior to genomic testing. Most mutations identified are missense and de novo. Many cases are heterozygous females, each with marked skewing of X-inactivation in peripheral blood DNA. We also identified eight hemizygous males who are more severely affected. The craniofacial appearance caused by HDAC8 mutations overlaps that of typical CdLS but often displays delayed anterior fontanelle closure, ocular hypertelorism, hooding of the eyelids, a broader nose and dental anomalies, which may be useful discriminating features. HDAC8 encodes the lysine deacetylase for the cohesin subunit SMC3 and analysis of the functional consequences of the missense mutations indicates that all cause a loss of enzymatic function. These data demonstrate that loss-of-function mutations in HDAC8 cause a range of overlapping human developmental phenotypes, including a phenotypically distinct subgroup of CdLS.

Mutations in PIGO, a member of the GPI-anchor-synthesis pathway, cause hyperphosphatasia with mental retardation.

Hyperphosphatasia with mental retardation syndrome (HPMRS), an autosomal-recessive form of intellectual disability characterized by facial dysmorphism, seizures, brachytelephalangy, and persistent elevated serum alkaline phosphatase (hyperphosphatasia), was recently shown to be caused by mutations in PIGV, a member of the glycosylphosphatidylinositol (GPI)-anchor-synthesis pathway. However, not all individuals with HPMRS harbor mutations in this gene. By exome sequencing, we detected compound-heterozygous mutations in PIGO, a gene coding for a membrane protein of the same molecular pathway, in two siblings with HPMRS, and we then found by Sanger sequencing further mutations in another affected individual; these mutations cosegregated in the investigated families. The mutant transcripts are aberrantly spliced, decrease the membrane stability of the protein, or impair enzyme function such that GPI-anchor synthesis is affected and the level of GPI-anchored substrates localized at the cell surface is reduced. Our data identify PIGO as the second gene associated with HPMRS and suggest that a deficiency in GPI-anchor synthesis is the underlying molecular pathomechanism of HPMRS.

Multicentric carpotarsal osteolysis is caused by mutations clustering in the amino-terminal transcriptional activation domain of MAFB.

Multicentric carpotarsal osteolysis (MCTO) is a rare skeletal dysplasia characterized by aggressive osteolysis, particularly affecting the carpal and tarsal bones, and is frequently associated with progressive renal failure. Using exome capture and next-generation sequencing in five unrelated simplex cases of MCTO, we identified previously unreported missense mutations clustering within a 51 base pair region of the single exon of MAFB, validated by Sanger sequencing. A further six unrelated simplex cases with MCTO were also heterozygous for previously unreported mutations within this same region, as were affected members of two families with autosomal-dominant MCTO. MAFB encodes a transcription factor that negatively regulates RANKL-induced osteoclastogenesis and is essential for normal renal development. Identification of this gene paves the way for development of novel therapeutic approaches for this crippling disease and provides insight into normal bone and kidney development.

A novel mutation (g.106737G>T) in zone of polarizing activity regulatory sequence (ZRS) causes variable limb phenotypes in Werner mesomelia.

Werner mesomelia is characterized by a sequence variation in the specific region (position 404) of the enhancer ZRS of SHH. The phenotype comprises variable mesomelia, abnormalities of the thumb and great toe and supernumerary digits. We describe extensive variation in limb phenotype in a large family and report on a novel sequence variation NG_009240.1: g.106737G>T (traditional nomenclature: ZRS404G>T) in the ZRS within the LMBR1 gene. The newly recognized clinical features in this family include small thenar eminence, sandal gap, broad first metatarsals, mesoaxial polydactyly, and postaxial polydactyly. We provide information on 12 affected family members. We review the literature on how a sequence variation in ZRS may cause such diverse phenotypes.

Mesomelia-synostoses syndrome results from deletion of SULF1 and SLCO5A1 genes at 8q13.

Mesomelia-synostoses syndrome (MSS) or mesomelic dysplasia with acral synostoses Verloes-David-Pfeiffer type is a rare autosomal-dominant disorder characterized by mesomelic limb shortening, acral synostoses, and multiple congenital malformations. So far, five patients in four unrelated families have been reported worldwide with MMS. By using whole-genome oligonucleotide array CGH, we have identified an interstitial deletion at 8q13 in all patients. The deletions vary from 582 Kb to 738 Kb in size, but invariably encompass only two genes: SULF1, encoding the heparan sulfate 6-O-endosulfatase 1, and SLCO5A1, encoding the solute carrier organic anion transporter family member 5A1. SULF1 acts as a regulator of numerous growth factors in skeletal embryonic development whereas the function of SLCO5A1 is yet unknown. Breakpoint sequence analyses performed in two families showed nonrecurrent deletions. Real-time quantitative RT-PCR analysis showed the highest levels of SULF1 transcripts in human osteoblasts and cartilage whereas SLCO5A1 was highly expressed in human fetal and adult brain and heart. Our results strongly suggest that haploinsufficiency of SULF1 contributes to this mesomelic chondrodysplasia, highlighting the critical role of endosulfatase in human skeletal development. Codeletion of SULF1 and SLCO5A1--which does not result from a low-copy repeats (LCRs)-mediated recombination event in at least two families--was found in all patients, so we suggest that haploinsufficiency of SULF1 combined with haploinsufficiency of SLCO5A1 (or the altered expression of a neighboring gene through position effect) could be necessary in the pathogenesis of MSS.

NEK1 and DYNC2H1 are both involved in short rib polydactyly Majewski type but not in Beemer Langer cases.

BACKGROUND: The lethal short rib polydactyly syndromes (SRP type I-IV) are characterised by notably short ribs, short limbs, polydactyly, multiple anomalies of major organs, and autosomal recessive mode of inheritance. Among them, SRP type II (Majewski; MIM 263520) is characterised by short ovoid tibiae or tibial agenesis and is radiographically closely related to SRP type IV (Beemer-Langer; MIM 269860) which is distinguished by bowed radii and ulnae and relatively well tubulated tibiae. NEK1 mutations have been recently identified in SRP type II. Double heterozygosity for mutations in both NEK1 and DYNC2H1 in one SRP type II case supported possible digenic diallelic inheritance. METHODS: The aim of this study was to screen DYNC2H1 and NEK1 in 13 SRP type II cases and seven SRP type IV cases. It was not possible to screen DYNC2H1 in two patients due to insufficient amount of DNA. RESULTS: The study identified homozygous NEK1 mutations in 5/13 SRP type II and compound heterozygous DYNC2H1 mutations in 4/12 cases. Finally, NEK1 and DYNC2H1 were excluded in 3/12 SRP type II and in all SRP type IV cases. The main difference between the mutation positive SRP type II group and the mutation negative SRP type II group was the presence of holoprosencephaly and polymycrogyria in the mutation negative group. CONCLUSION: This study confirms that NEK1 is one gene causing SRP type II but also reports mutations in DYNC2H1, expanding the phenotypic spectrum of DYNC2H1 mutations. The exclusion of NEK1 and DYNC2H1 in 3/12 SRP type II and in all SRP type IV cases further support genetic heterogeneity.

Loss-of-function mutations in LEMD3 result in osteopoikilosis, Buschke-Ollendorff syndrome and melorheostosis.

Osteopoikilosis, Buschke-Ollendorff syndrome (BOS) and melorheostosis are disorders characterized by increased bone density. The occurrence of one or more of these phenotypes in the same individual or family suggests that these entities might be allelic. We collected data from three families in which affected individuals had osteopoikilosis with or without manifestations of BOS or melorheostosis. A genome-wide linkage analysis in these families, followed by the identification of a microdeletion in an unrelated individual with these diseases, allowed us to map the gene that is mutated in osteopoikilosis. All the affected individuals that we investigated were heterozygous with respect to a loss-of-function mutation in LEMD3 (also called MAN1), which encodes an inner nuclear membrane protein. A somatic mutation in the second allele of LEMD3 could not be identified in fibroblasts from affected skin of an individual with BOS and an individual with melorheostosis. XMAN1, the Xenopus laevis ortholog, antagonizes BMP signaling during embryogenesis. In this study, LEMD3 interacted with BMP and activin-TGFbeta receptor-activated Smads and antagonized both signaling pathways in human cells.

Pseudoachondroplasia and multiple epiphyseal dysplasia: a 7-year comprehensive analysis of the known disease genes identify novel and recurrent mutations and provides an accurate assessment of their relative contribution.

Pseudoachondroplasia (PSACH) and multiple epiphyseal dysplasia (MED) are relatively common skeletal dysplasias resulting in short-limbed dwarfism, joint pain, and stiffness. PSACH and the largest proportion of autosomal dominant MED (AD-MED) results from mutations in cartilage oligomeric matrix protein (COMP); however, AD-MED is genetically heterogenous and can also result from mutations in matrilin-3 (MATN3) and type IX collagen (COL9A1, COL9A2, and COL9A3). In contrast, autosomal recessive MED (rMED) appears to result exclusively from mutations in sulphate transporter solute carrier family 26 (SLC26A2). The diagnosis of PSACH and MED can be difficult for the nonexpert due to various complications and similarities with other related diseases and often mutation analysis is requested to either confirm or exclude the diagnosis. Since 2003, the European Skeletal Dysplasia Network (ESDN) has used an on-line review system to efficiently diagnose cases referred to the network prior to mutation analysis. In this study, we present the molecular findings in 130 patients referred to ESDN, which includes the identification of novel and recurrent mutations in over 100 patients. Furthermore, this study provides the first indication of the relative contribution of each gene and confirms that they account for the majority of PSACH and MED.

Mutation-based growth charts for SEDC and other COL2A1 related dysplasias.

From data collected via a large international collaborative study, we have constructed a growth chart for patients with molecularly confirmed congenital spondylo-epiphyseal dysplasia (SEDC) and other COL2A1 related dysplasias. The growth chart is based on longitudinal height measurements of 79 patients with glycine substitutions in the triple-helical domain of COL2A1. In addition, measurements of 27 patients with other molecular defects, such as arginine to cysteine substitutions, splice mutations, and mutations in the C-terminal propeptide have been plotted on the chart. Height of the patients progressively deviate from that of normal children: compared to normal WHO charts, the mean length/height is -2.6 SD at birth, -4.2 SD at 5 years, and -5.8 SD in adulthood. The mean adult height (male and female combined) of patients with glycine substitutions in the triple-helical region is 138.2 cm but there is a large variation. Patients with glycine to cysteine substitutions tend to cluster within the upper part of the chart, while patients with glycine to serine or valine substitutions are situated between +1 SD and -1 SD. Patients with carboxy-terminal glycine substitutions tend to be shorter than patients with amino-terminal substitutions, while patients with splice mutations are relatively tall. However, there are exceptions and specific mutations can have a strong or a relatively mild negative effect on growth. The observation of significant difference in adult height between affected members of the same family indicates that height remains a multifactorial trait even in the presence of a mutation with a strong dominant effect.

Steel syndrome: Report of three patients, including monozygotic twins and review of clinical and mutation profiles.

Steel syndrome (MIM# 615155) is an autosomal recessive skeletal disorder, characterized by dislocations of the hips and radial heads, carpal coalition, short stature, facial dysmorphism, and scoliosis. Until date 47 patients have been reported. However, disease causing variants have been identified only in twenty Puerto Rican and nine non-Puerto Rican families. Here we report two monozygotic twins and a boy from two families with novel missense variants, c.295G > A p.(Ala99 Thr), c.3056C > A p.(Pro1019His) and c.2521G > A p.(Gly841Arg) in COL27A1. We describe for the first time, cleft palate and delayed carpal bone ossification as features of Steel syndrome. We reviewed clinical features in all mutation-proven Steel syndrome patients. Short stature and dislocation/subluxation of hip joint are consistently observed. Other features include dislocated radial heads, scoliosis, lordosis, carpal coalition, facial dysmorphism, hearing loss, bilateral fifth finger clinodactyly, knee deformities and developmental delay. Seven missense variants and eight null variants are reported in COL27A1 until date. We also looked into the genotype-phenotype correlation in Puerto Rican and non-Puerto Rican patients.

International Consensus Statement on the diagnosis, multidisciplinary management and lifelong care of individuals with achondroplasia.

Achondroplasia, the most common skeletal dysplasia, is characterized by a variety of medical, functional and psychosocial challenges across the lifespan. The condition is caused by a common, recurring, gain-of-function mutation in FGFR3, the gene that encodes fibroblast growth factor receptor 3. This mutation leads to impaired endochondral ossification of the human skeleton. The clinical and radiographic hallmarks of achondroplasia make accurate diagnosis possible in most patients. However, marked variability exists in the clinical care pathways and protocols practised by clinicians who manage children and adults with this condition. A group of 55 international experts from 16 countries and 5 continents have developed consensus statements and recommendations that aim to capture the key challenges and optimal management of achondroplasia across each major life stage and sub-specialty area, using a modified Delphi process. The primary purpose of this first International Consensus Statement is to facilitate the improvement and standardization of care for children and adults with achondroplasia worldwide in order to optimize their clinical outcomes and quality of life.

Genotype-phenotype analysis of the branchio-oculo-facial syndrome.

Branchio-oculo-facial syndrome (BOFS; OMIM#113620) is a rare autosomal dominant craniofacial disorder with variable expression. Major features include cutaneous and ocular abnormalities, characteristic facies, renal, ectodermal, and temporal bone anomalies. Having determined that mutations involving TFAP2A result in BOFS, we studied a total of 30 families (41 affected individuals); 26/30 (87%) fulfilled our cardinal diagnostic criteria. The original family with the 3.2 Mb deletion including the TFAP2A gene remains the only BOFS family without the typical CL/P and the only family with a deletion. We have identified a hotspot region in the highly conserved exons 4 and 5 of TFAP2A that harbors missense mutations in 27/30 (90%) families. Several of these mutations are recurrent. Mosaicism was detected in one family. To date, genetic heterogeneity has not been observed. Although the cardinal criteria for BOFS have been based on the presence of each of the core defects, an affected family member or thymic remnant, we documented TFAP2A mutations in three (10%) probands in our series without a classic cervical cutaneous defect or ectopic thymus. Temporal bone anomalies were identified in 3/5 patients investigated. The occurrence of CL/P, premature graying, coloboma, heterochromia irides, and ectopic thymus, are evidence for BOFS as a neurocristopathy. Intrafamilial clinical variability can be marked. Although there does not appear to be mutation-specific genotype-phenotype correlations at this time, more patients need to be studied. Clinical testing for TFAP2A mutations is now available and will assist geneticists in confirming the typical cases or excluding the diagnosis in atypical cases.