CHST3-related skeletal dysplasia in 14 patients: Identification of 8 novel variants and further expansion of the phenotypic spectrum.

Biallelic variants in CHST3 gene result in congenital dislocation of large joints, club feet, short stature, rhizomelia, kypho-scoliosis, platyspondyly, epiphyseal dysplasia, flared metaphysis, in addition to minor cardiac lesions and hearing loss. Herein, we describe 14 new patients from 11 unrelated Egyptian families with CHST3-related skeletal dysplasia. All patients had spondyloepiphyseal changes that were progressive with age in addition to bifid distal ends of humeri which can be considered a diagnostic key in patients with CHST3 variants. They also shared peculiar facies with broad forehead, broad nasal tip, long philtrum and short neck. Rare unusual associated findings included microdontia, teeth spacing, delayed eruption, prominent angulation of the lumbar-sacral junction and atrial septal defect. Mutational analysis revealed 10 different homozygous CHST3 (NM_004273.5) variants including 7 missense, two frameshift and one nonsense variant. Of them, the c.384_391dup (p.Pro131Argfs*88) was recurrent in two families. Eight of these variants were not described before. Our study presents the largest series of patients with CHST3-related skeletal dysplasia from the same ethnic group. Furthermore, it reinforces that lethal cardiac involvement is a critical clinical finding of the disorder. Therefore, we believe that our study expands the phenotypic and mutational spectrum, and also highlights the importance of performing echocardiography in patients harboring CHST3 variants.

Shohat type-spondyloepimetaphyseal dysplasia: Further phenotypic delineation.

Spondyloepimetaphyseal dysplasia-Shohat type (SEMDSH) is an ultra-rare type of skeletal dysplasia. Only nine patients from six families have been reported and genetically confirmed to have biallelic pathogenic variants in the DDRGK1 gene. We present a patient with typical clinical features of the disorder, including disproportionate short-limbed short stature, short neck, short chest with pectus carinatum, exaggerated lumbar lordosis and marked genu vara. Our patient further showed microcephaly, unilateral choanal atresia and antenatal fractures, features that were not reported before in association with this disorder. Radiological changes over time were presented, including delayed epiphyseal ossification, broad metaphysis with marked irregularities that progressed with age, fibular overgrowth, and characteristic spine changes with early platyspondyly and squaring of vertebral bodies at a later age. Exome sequencing revealed a homozygous pathogenic donor splice site variant in the DDRGK1 gene (NM_023935.3:c.408+1G > A). This mutation was also previously identified in patients from Iraqi descent. Our study expands the phenotypic spectrum of SEMDSH, emphasizes the radiological changes with age in SEMDSH patients, and recommends prolonged follow-up for these cases better to delineate the phenotype and surveillance for possible complications.

Mutations in SCNM1 cause orofaciodigital syndrome due to minor intron splicing defects affecting primary cilia.

Orofaciodigital syndrome (OFD) is a genetically heterogeneous ciliopathy characterized by anomalies of the oral cavity, face, and digits. We describe individuals with OFD from three unrelated families having bi-allelic loss-of-function variants in SCNM1 as the cause of their condition. SCNM1 encodes a protein recently shown to be a component of the human minor spliceosome. However, so far the effect of loss of SCNM1 function on human cells had not been assessed. Using a comparative transcriptome analysis between fibroblasts derived from an OFD-affected individual harboring SCNM1 mutations and control fibroblasts, we identified a set of genes with defective minor intron (U12) processing in the fibroblasts of the affected subject. These results were reproduced in SCNM1 knockout hTERT RPE-1 (RPE-1) cells engineered by CRISPR-Cas9-mediated editing and in SCNM1 siRNA-treated RPE-1 cultures. Notably, expression of TMEM107 and FAM92A encoding primary cilia and basal body proteins, respectively, and that of DERL2, ZC3H8, and C17orf75, were severely reduced in SCNM1-deficient cells. Primary fibroblasts containing SCNM1 mutations, as well as SCNM1 knockout and SCNM1 knockdown RPE-1 cells, were also found with abnormally elongated cilia. Conversely, cilia length and expression of SCNM1-regulated genes were restored in SCNM1-deficient fibroblasts following reintroduction of SCNM1 via retroviral delivery. Additionally, functional analysis in SCNM1-retrotransduced fibroblasts showed that SCNM1 is a positive mediator of Hedgehog (Hh) signaling. Our findings demonstrate that defective U12 intron splicing can lead to a typical ciliopathy such as OFD and reveal that primary cilia length and Hh signaling are regulated by the minor spliceosome through SCNM1 activity.

Bruck syndrome in 13 new patients: Identification of five novel FKBP10 and PLOD2 variants and further expansion of the phenotypic spectrum.

Bruck Syndrome (BS) is a very rare disorder characterized by osteogenesis imperfecta (OI) associated with congenital contractures and is caused by mutations in FKBP10 or PLOD2 genes. Herein, we describe 13 patients from 9 unrelated Egyptian families with BS. All patients had white sclerae, recurrent fractures, kyphoscoliosis and osteoporosis with variable degrees of severity. Large joint contractures were seen in 11 patients, one patient had contractures of small interphalangeal joints, and one patient had no contractures. Unusual findings noted in individual patients included microcephaly, dental malocclusion, enamel hypoplasia, unilateral congenital dislocation of knee joint, prominent tailbone, and myopathy. Nine different variants were identified in FKBP10 and PLOD2 including five novel ones. FKBP10 variants were found in six families (67%) while PLOD2 variants were identified in three families (33%). The four families, with two affected sibs each, showed inter- and intrafamilial phenotypic variability. In conclusion, we report five novel variants in FKBP10 and PLOD2 thus, expanding the mutational spectrum of BS. In addition, our results expand the phenotypic spectrum, describe newly associated orodental findings, and further illustrate the phenotypic overlap between OI and Bruck syndrome supporting the suggestion of considering BS as a variant of OI rather than a separate entity.

Osteoporosis-pseudoglioma syndrome in four new patients: identification of two novel LRP5 variants and insights on patients' management using bisphosphonates therapy.

This study describes the clinical, radiological, and molecular data of four new patients with osteoporosis-pseudoglioma syndrome and assesses their response to bisphosphonate therapy. INTRODUCTION: Osteoporosis-pseudoglioma syndrome (OPPG) is a very rare disorder characterized mainly by severe juvenile osteoporosis and congenital blindness. OPPG is caused by biallelic mutations in the gene encoding low-density lipoprotein receptor-related protein 5 (LRP5). METHODS: We present the clinical, radiological, and molecular findings of four new patients with OPPG from Egypt. We also assessed patients' response to oral and intravenous bisphosphonate therapy. RESULTS: All patients had reduced bone mineral density (BMD) with variable number of fractures per year, in addition to bone abnormalities and the characteristic eye phenotype associated with OPPG. Mutation analyses of LRP5 gene revealed three different homozygous variants including two novel ones, c.7delG (p.A3Qfs*80) and c.3280G > A (p.E1094K). The c.3280G > A (p.E1094K) was recurrent in two unrelated patients who shared a unique haplotype suggesting a possible founder effect. The use of bisphosphonate therapy was beneficial; however, intravenous bisphosphonate administration led to a more favorable response. CONCLUSION: Our study described the phenotypic and genetic features of four patients with OPPG and identified two new LRP5 variants, thus expanding the mutational spectrum of OPPG. In addition, our study reinforces the efficiency of using intravenous bisphosphonates in the management of patients with OPPG.

Two new patients with focal dermal hypoplasia: A novel PORCN variant and insights on the diagnostic considerations.

Mutations in the PORCN gene cause an X-linked dominant condition; focal dermal hypoplasia (FDH), characterized by atrophic skin, pigmented skin lesions in addition to several ocular and skeletal malformations. FDH is rare with around 275 cases reported so far from diverse ethnic groups. Herein, we provide a report of two new patients with FDH from Egypt. In addition to the typical clinical manifestations of the disease, infrequently reported clinical findings in the form of broad metaphysis, bilateral short broad femurs, and dermal sinus over the sacrum were seen in Patient 1 and partial fusion of labia majora, ventral hernia, and bladder extrophy were present in Patient 2. Two heterozygous protein-truncating PORCN mutations were identified in our patients, a known nonsense c.370C>T p.(Arg124Ter) and a novel frameshift c.375delG p.(Ala126HisfsTer3). Segregation analyses confirmed that the two mutations were "de novo" and not inherited from any of the parents. Our study expands the clinical and mutational spectrum of focal dermal hypoplasia and emphasizes the importance of investigating the different body systems and organs for the early management of patients.

First Report of Two Egyptian Patients with Desbuquois Dysplasia due to Homozygous CANT1 Mutations.

Desbuquois dysplasia type 1 (DBQD1) is a very rare skeletal dysplasia characterized by growth retardation, short stature, distinct hand features, and a characteristic radiological monkey wrench appearance at the proximal femur. We report on 2unrelated Egyptian patients having the characteristic features of DBQD1 with different expressivity. Patient 1 presented at the age of 45 days with respiratory distress, short limbs, faltering growth, and distinctive facies while patient 2 presented at 5 years of age with short stature and hypospadias. The 2 patients shared radiological features suggestive of DBQD1. Whole-exome sequencing revealed a homozygous frameshift mutation in the CANT1 gene (NM_001159772.1:c.277_278delCT; p.Leu93ValfsTer89) in patient 1 and a homozygous missense mutation (NM_138793.4:c.898C>T; p.Arg300Cys) in patient 2. Phenotypic variability and variable expressivity of DBQD was evident in our patients. Hypoplastic scrotum and hypospadias were additional unreported associated findings, thus expanding the phenotypic spectrum of the disorder. We reviewed the main features of skeletal dysplasias exhibiting similar radiological manifestations for differential diagnosis. We suggest that the variable severity in both patients could be due to the nature of the CANT1 gene mutations which necessitates the molecular study of more cases for phenotype-genotype correlations.

Chromosome 9p terminal deletion in nine Egyptian patients and narrowing of the critical region for trigonocephaly.

BACKGROUND: This study aimed to delineate the clinical phenotype of patients with 9p deletions, pinpoint the chromosomal breakpoints, and identify the critical region for trigonocephaly, which is a frequent finding in 9p terminal deletion. METHODS: We investigated a cohort of nine patients with chromosome 9p terminal deletions who all displayed developmental delay, intellectual disability, hypotonia, and dysmorphic features. Of them, eight had trigonocephaly, seven had brain anomalies, seven had autistic manifestations, seven had fair hair, and six had a congenital heart defect (CHD). RESULTS: Karyotyping revealed 9p terminal deletion in all patients, and patients 8 and 9 had additional duplication of other chromosomal segments. We used six bacterial artificial chromosome (BAC) clones that could identify the breakpoints at 17-20 Mb from the 9p terminus. Array CGH identified the precise extent of the deletion in six patients; the deleted regions ranged from 16 to 18.8 Mb in four patients, patient 8 had an 11.58 Mb deletion and patient 9 had a 2.3 Mb deletion. CONCLUSION: The gene deletion in the 9p24 region was insufficient to cause ambiguous genitalia because six of the nine patients had normal genitalia. We suggest that the critical region for trigonocephaly lies between 11,575 and 11,587 Mb from the chromosome 9p terminus. To the best of our knowledge, this is the minimal critical region reported for trigonocephaly in 9p deletion syndrome, and it warrants further delineation.

3D assessment of intervertebral disc degeneration in zebrafish identifies changes in bone density that prime disc disease.

Back pain is a common condition with a high social impact and represents a global health burden. Intervertebral disc disease (IVDD) is one of the major causes of back pain; no therapeutics are currently available to reverse this disease. The impact of bone mineral density (BMD) on IVDD has been controversial, with some studies suggesting osteoporosis as causative for IVDD and others suggesting it as protective for IVDD. Functional studies to evaluate the influence of genetic components of BMD in IVDD could highlight opportunities for drug development and repurposing. By taking a holistic 3D approach, we established an aging zebrafish model for spontaneous IVDD. Increased BMD in aging, detected by automated computational analysis, is caused by bone deformities at the endplates. However, aged zebrafish spines showed changes in bone morphology, microstructure, mineral heterogeneity, and increased fragility that resembled osteoporosis. Elements of the discs recapitulated IVDD symptoms found in humans: the intervertebral ligament (equivalent to the annulus fibrosus) showed disorganized collagen fibers and herniation, while the disc center (nucleus pulposus equivalent) showed dehydration and cellular abnormalities. We manipulated BMD in young zebrafish by mutating sp7 and cathepsin K, leading to low and high BMD, respectively. Remarkably, we detected IVDD in both groups, demonstrating that low BMD does not protect against IVDD, and we found a strong correlation between high BMD and IVDD. Deep learning was applied to high-resolution synchrotron µCT image data to analyze osteocyte 3D lacunar distribution and morphology, revealing a role of sp7 in controlling the osteocyte lacunar 3D profile. Our findings suggest potential avenues through which bone quality can be targeted to identify beneficial therapeutics for IVDD.

Biallelic truncating variants in MAPKAPK5 cause a new developmental disorder involving neurological, cardiac, and facial anomalies combined with synpolydactyly.

PURPOSE: This study aimed to identify the genetic cause of a new multiple congenital anomalies syndrome observed in three individuals from two unrelated families. METHODS: Clinical assessment was conducted prenatally and at different postnatal stages. Genetic studies included exome sequencing (ES) combined with single-nucleotide polymorphism (SNP) array based homozygosity mapping and trio ES. Dermal fibroblasts were used for functional assays. RESULTS: A clinically recognizable syndrome characterized by severe developmental delay, variable brain anomalies, congenital heart defects, dysmorphic facial features, and a distinctive type of synpolydactyly with an additional hypoplastic digit between the fourth and fifth digits of hands and/or feet was identified. Additional features included eye abnormalities, hearing impairment, and electroencephalogram anomalies. ES detected different homozygous truncating variants in MAPKAPK5 in both families. Patient-derived cells showed no expression of MAPKAPK5 protein isoforms and reduced levels of the MAPKAPK5-interacting protein ERK3. F-actin recovery after latrunculin B treatment was found to be less efficient in patient-derived fibroblasts than in control cells, supporting a role of MAPKAPK5 in F-actin polymerization. CONCLUSION: Our data indicate that loss-of-function variants in MAPKAPK5 result in a severe developmental disorder and reveal a major role of this gene in human brain, heart, and limb development.

Germline and Mosaic Variants in PRKACA and PRKACB Cause a Multiple Congenital Malformation Syndrome.

PRKACA and PRKACB code for two catalytic subunits (Cα and Cß) of cAMP-dependent protein kinase (PKA), a pleiotropic holoenzyme that regulates numerous fundamental biological processes such as metabolism, development, memory, and immune response. We report seven unrelated individuals presenting with a multiple congenital malformation syndrome in whom we identified heterozygous germline or mosaic missense variants in PRKACA or PRKACB. Three affected individuals were found with the same PRKACA variant, and the other four had different PRKACB mutations. In most cases, the mutations arose de novo, and two individuals had offspring with the same condition. Nearly all affected individuals and their affected offspring shared an atrioventricular septal defect or a common atrium along with postaxial polydactyly. Additional features included skeletal abnormalities and ectodermal defects of variable severity in five individuals, cognitive deficit in two individuals, and various unusual tumors in one individual. We investigated the structural and functional consequences of the variants identified in PRKACA and PRKACB through the use of several computational and experimental approaches, and we found that they lead to PKA holoenzymes which are more sensitive to activation by cAMP than are the wild-type proteins. Furthermore, expression of PRKACA or PRKACB variants detected in the affected individuals inhibited hedgehog signaling in NIH 3T3 fibroblasts, thereby providing an underlying mechanism for the developmental defects observed in these cases. Our findings highlight the importance of both Cα and Cß subunits of PKA during human development.

Blepharophimosis-ptosis-intellectual disability syndrome: A report of nine Egyptian patients with further expansion of phenotypic and mutational spectrum.

Blepharophimosis-ptosis-intellectual disability syndrome (BPID) is an extremely rare recognizable blepharophimosis intellectual disability syndrome (BID). It is caused by biallelic variants in the UBE3B gene with only 24 patients described worldwide. Herein, we report on the clinical, brain imaging and molecular findings of additional nine patients from six unrelated Egyptian families. Patients presented with the characteristic features of the syndrome including blepharophimosis, ptosis, upslanted palpebral fissures with epicanthic folds, hypertelorism, long philtrum, high arched palate, micrognathia, microcephaly, and intellectual disability. Other findings were congenital heart disease (5 patients), talipes equinovarus (5 patients), genital anomalies (5 patients), autistic features (4 patients), cleft palate (2 patients), hearing loss (2 patients), and renal anomalies (1 patient). New or rarely reported findings were spherophakia, subvalvular aortic stenosis and hypoplastic nails, and terminal phalanges. Brain MRI, performed for 7 patients, showed hypogenesis or almost complete agenesis of corpus callosum. Genetic studies revealed five novel homozygous UBE3B variants. Of them, the c.1076G>A (p.W359*) was found in three patients from two unrelated families who shared similar haplotype suggesting a likely founder effect. Our results strengthen the clinical, dysmorphic, and brain imaging characteristic of this unique type of BID and extend the mutational spectrum associated with the disorder.

Heterozygous pathogenic variants in GLI1 are a common finding in isolated postaxial polydactyly A/B.

Postaxial polydactyly (PAP) is a frequent limb malformation consisting in the duplication of the fifth digit of the hand or foot. Morphologically, this condition is divided into type A and B, with PAP-B corresponding to a more rudimentary extra-digit. Recently, biallelic truncating variants in the transcription factor GLI1 were reported to be associated with a recessive disorder, which in addition to PAP-A, may include syndromic features. Moreover, two heterozygous subjects carrying only one inactive copy of GLI1 were also identified with PAP. Herein, we aimed to determine the level of involvement of GLI1 in isolated PAP, a condition previously established to be autosomal dominantly inherited with incomplete penetrance. We analyzed the coding region of GLI1 in 95 independent probands with nonsyndromic PAP and found 11.57% of these subjects with single heterozygous pathogenic variants in this gene. The detected variants lead to premature termination codons or result in amino acid changes in the DNA-binding domain of GLI1 that diminish its transactivation activity. Family segregation analysis of these variants was consistent with dominant inheritance with incomplete penetrance. We conclude that heterozygous changes in GLI1 underlie a significant proportion of sporadic or familial cases of isolated PAP-A/B.

Cellular stress due to impairment of collagen prolyl hydroxylation complex is rescued by the chaperone 4-phenylbutyrate.

Osteogenesis imperfecta (OI) types VII, VIII and IX, caused by recessive mutations in cartilage-associated protein (CRTAP), prolyl-3-hydroxylase 1 (P3H1) and cyclophilin B (PPIB), respectively, are characterized by the synthesis of overmodified collagen. The genes encode for the components of the endoplasmic reticulum (ER) complex responsible for the 3-hydroxylation of specific proline residues in type I collagen. Our study dissects the effects of mutations in the proteins of the complex on cellular homeostasis, using primary fibroblasts from seven recessive OI patients. In all cell lines, the intracellular retention of overmodified type I collagen molecules causes ER enlargement associated with the presence of protein aggregates, activation of the PERK branch of the unfolded protein response and apoptotic death. The administration of 4-phenylbutyrate (4-PBA) alleviates cellular stress by restoring ER cisternae size, and normalizing the phosphorylated PERK (p-PERK):PERK ratio and the expression of apoptotic marker. The drug also has a stimulatory effect on autophagy. We proved that the rescue of cellular homeostasis following 4-PBA treatment is associated with its chaperone activity, since it increases protein secretion, restoring ER proteostasis and reducing PERK activation and cell survival also in the presence of pharmacological inhibition of autophagy. Our results provide a novel insight into the mechanism of 4-PBA action and demonstrate that intracellular stress in recessive OI can be alleviated by 4-PBA therapy, similarly to what we recently reported for dominant OI, thus allowing a common target for OI forms characterized by overmodified collagen.This article has an associated First Person interview with the first author of the paper.

Recessive mutations in muscle-specific isoforms of FXR1 cause congenital multi-minicore myopathy.

FXR1 is an alternatively spliced gene that encodes RNA binding proteins (FXR1P) involved in muscle development. In contrast to other tissues, cardiac and skeletal muscle express two FXR1P isoforms that incorporate an additional exon-15. We report that recessive mutations in this particular exon of FXR1 cause congenital multi-minicore myopathy in humans and mice. Additionally, we show that while Myf5-dependent depletion of all FXR1P isoforms is neonatal lethal, mice carrying mutations in exon-15 display non-lethal myopathies which vary in severity depending on the specific effect of each mutation on the protein.

GAPO syndrome in seven new patients: Identification of five novel ANTXR1 mutations including the first large intragenic deletion.

GAPO syndrome is a very rare disorder characterized by growth retardation, alopecia, pseudoanodontia and progressive optic atrophy. It is caused by biallelic mutations in the ANTXR1 gene. Herein, we describe the clinical and molecular findings of seven new patients with GAPO syndrome. Our patients presented with the characteristic clinical features of the syndrome except for one patient who did not display total alopecia till the age of two years. Strikingly, optic atrophy and glaucoma were observed in all patients and one patient showed keratopathy in addition. Moreover, craniosynstosis was an unusual associated finding in one patient. Mutational analysis of ANTXR1 gene identified five novel homozygous mutations including two frameshift, two splice site and a large intragenic deletion of exon 3. Our results reinforce the clinical characteristics of the syndrome, expand the mutational spectrum and provide more insights into the role of the ANTXR1 protein in the regulation of extracellular matrix.

Expanding the phenome and variome of skeletal dysplasia.

PURPOSE: To describe our experience with a large cohort (411 patients from 288 families) of various forms of skeletal dysplasia who were molecularly characterized. METHODS: Detailed phenotyping and next-generation sequencing (panel and exome). RESULTS: Our analysis revealed 224 pathogenic/likely pathogenic variants (54 (24%) of which are novel) in 123 genes with established or tentative links to skeletal dysplasia. In addition, we propose 5 genes as candidate disease genes with suggestive biological links (WNT3A, SUCO, RIN1, DIP2C, and PAN2). Phenotypically, we note that our cohort spans 36 established phenotypic categories by the International Skeletal Dysplasia Nosology, as well as 18 novel skeletal dysplasia phenotypes that could not be classified under these categories, e.g., the novel C3orf17-related skeletal dysplasia. We also describe novel phenotypic aspects of well-known disease genes, e.g., PGAP3-related Toriello-Carey syndrome-like phenotype. We note a strong founder effect for many genes in our cohort, which allowed us to calculate a minimum disease burden for the autosomal recessive forms of skeletal dysplasia in our population (7.16E-04), which is much higher than the global average. CONCLUSION: By expanding the phenotypic, allelic, and locus heterogeneity of skeletal dysplasia in humans, we hope our study will improve the diagnostic rate of patients with these conditions.

FAM46A mutations are responsible for autosomal recessive osteogenesis imperfecta.

BACKGROUND: Stüve-Wiedemann syndrome (SWS) is characterised by bowing of the lower limbs, respiratory distress and hyperthermia that are often responsible for early death. Survivors develop progressive scoliosis and spontaneous fractures. We previously identified LIFR mutations in most SWS cases, but absence of LIFR pathogenic changes in five patients led us to perform exome sequencing and to identify homozygosity for a FAM46A mutation in one case [p.Ser205Tyrfs*13]. The follow-up of this case supported a final diagnosis of osteogenesis imperfecta (OI), based on vertebral collapses and blue sclerae. METHODS AND RESULTS: This prompted us to screen FAM46A in 25 OI patients with no known mutations.We identified a homozygous deleterious variant in FAM46A in two affected sibs with typical OI [p.His127Arg]. Another homozygous variant, [p.Asp231Gly], also classed as deleterious, was detected in a patient with type III OI of consanguineous parents using homozygosity mapping and exome sequencing.FAM46A is a member of the superfamily of nucleotidyltransferase fold proteins but its exact function is presently unknown. Nevertheless, there are lines of evidence pointing to a relevant role of FAM46A in bone development. By RT-PCR analysis, we detected specific expression of FAM46A in human osteoblasts andinterestingly, a nonsense mutation in Fam46a has been recently identified in an ENU-derived (N-ethyl-N-nitrosourea) mouse model characterised by decreased body length, limb, rib, pelvis, and skull deformities and reduced cortical thickness in long bones. CONCLUSION: We conclude that FAM46A mutations are responsible for a severe form of OI with congenital bowing of the lower limbs and suggest screening this gene in unexplained OI forms.

Gnathodiaphyseal dysplasia: Severe atypical presentation with novel heterozygous mutation of the anoctamin gene (ANO5).

Gnathodiaphyseal dysplasia (GDD; OMIM #166260) is an ultra-rare autosomal dominant disorder caused by heterozygous mutation in the anoctamin 5 (ANO5) gene and features fibro-osseous lesions of the jawbones, bone fragility with recurrent fractures, and bowing/sclerosis of tubular bones. The physiologic role of ANO5 is unknown. We report a 5-year-old boy with a seemingly atypical and especially severe presentation of GDD and unique ANO5 mutation. Severe osteopenia was associated with prenatal femoral fractures, recurrent postnatal fractures, and progressive bilateral enlargement of his maxilla and mandible beginning at ~2months-of-age that interfered with feeding and speech and required four debulking operations. Histopathological analysis revealed benign fibro-osseous lesions resembling cemento-ossifying fibromas of the jaw without psammomatoid bodies. A novel, de novo, heterozygous, missense mutation was identified in exon 15 of ANO5 (c.1553G>A; p.Gly518Glu). Our findings broaden the phenotypic and molecular spectra of GDD. Fractures early in life with progressive facial swelling are key features. We assessed his response to a total of 7 pamidronate infusions commencing at age 15months. Additional reports must further elucidate the phenotype, explore any genotype-phenotype correlation, and evaluate treatments.

A novel frameshift mutation in the sterol 27-hydroxylase gene in an Egyptian family with cerebrotendinous xanthomatosis without cataract.

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive lipid storage disorder caused by deficiency of the mitochondrial cytochrome P450 sterol 27-hydroxylase enzyme encoded by CYP27A1 gene. CTX is characterized by tendon xanthomas, juvenile cataracts and multiple progressive neurological symptoms. Here we report on the clinical and molecular findings of a 35-years old Egyptian patient with CTX without cataract. Parents were first cousins with family history of two deceased sibs with mild impaired cognitive functions and epilepsy without appearance of tendon xanthomas. Our proband had learning disabilities and developed seizures at 9 years old. Tendon xanthomata appeared at the age of 16 and his neurological symptoms remained stationary till 28 years followed by progressive cerebello-pyramidal signs, dementia and psychiatric disturbance. Cataract was not evident in our patient. Brain MRI showed the characteristic focal lesions appeared as xanthomas in cerebellum and occipital horns of lateral ventricles. Molecular study identified a novel homozygous frameshift mutation in CYP27A1 gene, c.1169delT (p.K391Rfs*17). Our study emphasizes the important role of early genetic testing in prevention of morbidity and mortality of the disease and proper counseling. Moreover, it shows that the absence of cataract should not rule out the diagnosis of CTX.