A spectrum of TP63-related disorders with eight affected individuals in five unrelated families.

TP63-related disdorders broadly involve varying combinations of ectodermal dysplasia (sparse hair, hypohydrosis, tooth abnormalities, nail dysplasia), cleft lip/palate, acromelic malformation, split-hand/foot malformation/syndactyly, ankyloblepharon filiforme adnatum, lacrimal duct obstruction, hypopigmentation, and hypoplastic breasts and/or nipples. TP63-related disorders are associated with heterozygous pathogenic variants in TP63 and include seven overlapping phenotypes; Ankyloblepharon-ectodermal defects-cleft lip/palate syndrome (AEC), Ectrodactyly-ectodermal dysplasia-cleft lip/palate syndrome 3 (EEC3), Limb-mammary syndrome (LMS), Acro-dermo-ungual-lacrimal-tooth syndrome (ADULT), Rapp-Hodgkin syndrome (RHS), Split-hand/foot malformation 4 (SHFM4), and Orofacial cleft 8. We report on five unrelated families with 8 affected individuals in which the probands presented with varying combinations of ectodermal dysplasia, cleft lip/palate, split-hand/foot malformation, lacrimal duct obstruction, and ankyloblepharon filiforme adnatum. The clinical diagnosis involved AEC syndrome (2 patients), EEC3 syndrome (2 patients), and a yet hitherto unclassified TP63-related disorder. Sanger sequence analysis of the TP63 gene was performed revealing five different variants among which four were novel and three were de novo. The identificated TP63 variants co-segregated with the other affected individuals in the families. The abnormalities of ectoderm derived structures including hair, nails, sweat glands, and teeth should alert the physician to the possibility of TP63-related disorders particularly in the presence of orofacial clefting.

Evaluation of polysomnography findings in children with genetic skeletal disorders.

Children with genetic skeletal disorders have variable conditions that can lead to sleep-disordered breathing, and polysomnography is the gold standard for diagnosing this condition. We aimed to review polysomnography findings, to assess the severity of sleep apnea, and to investigate the clinical variables predictive of sleep-disordered breathing in these patients. We retrospectively collected the medical records of patients with genetic skeletal disorders who underwent polysomnography for 5 years. Twenty-seven children with various genetic skeletal disorders, including achondroplasia (14), Crouzon syndrome (3), acromesomelic dysplasia Maroteaux type (3), Apert syndrome (2), osteopetrosis (1), Jeune dysplasia (1), Desbuquois dysplasia (1), acrodysostosis (1), and spondyloepiphyseal dysplasia (1) were enrolled. The median age at the first polysomnography was 58 (1st-3rd quartile: 31-113) months. The overall sleep-disordered breathing results were: 19 (70.3%) had obstructive sleep apneas (OSA) (4 mild, 6 moderate, 9 severe), 2 (7.4%) had central apneas, 4 (14.8%) had nocturnal hypoventilation. There was a significant correlation between non-ambulatory status with both total AHI and OSA (p < 0.001, rho: -0.66/p = 0.04, rho: 0.38, respectively). Nine patients received positive airway pressure titration, and the oAHI values of all returned to the normal range. These patients were started with positive airway pressure treatment. Our cohort showed that the majority of the patients with skeletal dysplasia had sleep apnea syndrome characterised mainly by OSA, highlighting the importance of polysomnography screening for sleep disorders. Positive airway pressure therapy represents an effective treatment for sleep-disordered breathing in those patients.

Al-Gazali Skeletal Dysplasia Constitutes the Lethal End of ADAMTSL2-Related Disorders.

Lethal short-limb skeletal dysplasia Al-Gazali type (OMIM %601356), also called dysplastic cortical hyperostosis, Al-Gazali type, is an ultra-rare disorder previously reported in only three unrelated individuals. The genetic etiology for Al-Gazali skeletal dysplasia has up until now been unknown. Through international collaborative efforts involving seven clinical centers worldwide, a cohort of nine patients with clinical and radiographic features consistent with short-limb skeletal dysplasia Al-Gazali type was collected. The affected individuals presented with moderate intrauterine growth restriction, relative macrocephaly, hypertrichosis, large anterior fontanelle, short neck, short and stiff limbs with small hands and feet, severe brachydactyly, and generalized bone sclerosis with mild platyspondyly. Biallelic disease-causing variants in ADAMTSL2 were detected using massively parallel sequencing (MPS) and Sanger sequencing techniques. Six individuals were compound heterozygous and one individual was homozygous for pathogenic variants in ADAMTSL2. In one of the families, pathogenic variants were detected in parental samples only. Overall, this study sheds light on the genetic cause of Al-Gazali skeletal dysplasia and identifies it as a semi-lethal part of the spectrum of ADAMTSL2-related disorders. Furthermore, we highlight the importance of meticulous analysis of the pseudogene region of ADAMTSL2 where disease-causing variants might be located. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

A novel biallelic CRIPT variant in a patient with short stature, microcephaly, and distinctive facial features.

Primordial dwarfism (PD) is one of a highly heterogeneous group of disorders characterized by severe prenatal/postnatal growth restriction. Defects in various pathways such as DNA repair mechanism, impaired centrioles, abnormal IGF expression, and spliceosomal machinery may cause PD including Seckel syndrome, Silver-Russell syndrome. Microcephalic osteodysplastic primordial dwarfism (MOPD) types I/III, II, and Meier-Gorlin syndrome. In recent years with the wide application of exome sequencing (ES) in the field of PD, new genes involved in novel pathways causing new phenotypes have been identified. Pathogenic variants in CRIPT (MIM# 604594) encoding cysteine-rich PDZ domain-binding protein have recently been described in patients with PD with a unique phenotype. This phenotype is characterized by prenatal/postnatal growth restriction, facial dysmorphism, ocular abnormalities, and ectodermal findings such as skin lesions with hyper/hypopigmented patchy areas and hair abnormalities. To our knowledge, only three patients with homozygous or compound heterozygous variants in CRIPT have been reported so far. Here, we report on a male patient who presented with profound prenatal/postnatal growth restriction, developmental delay, dysmorphic facial features, and skin lesions along with the findings of bicytopenia and extensive retinal pigmentation defect. A novel truncating homozygous variant c.7_8delTG; p.(Cys3Argfs*4) was detected in CRIPT with the aid of ES. With this report, we further expand the mutational and clinical spectrum of this rare entity.

Typical Face, Developmental Delay, and Hearing Loss in a Patient with 3M Syndrome: The Co-Occurrence of Two Rare Conditions.

Introduction: 3M syndrome is an autosomal recessive disorder characterized by characteristic facial features, severe pre- and postnatal growth restriction (<-4 SDS), and normal mental development. 3M syndrome is genetically heterogeneous. Up to date, causative mutations have been demonstrated in 3 genes, cullin-7 (CUL7), obscurin-like 1 (OBSL1), and coiled coil domain containing protein 8 (CCDC8). Case presentation: Here, we report a patient who was referred to our clinic due to short stature and developmental delay. Physical examination revealed prenatal onset short stature, low birth weight, and normal head circumference. She displayed several dysmorphic facial features in addition to developmental delay and bilateral sensorineural hearing loss. The physical findings were suggestive of 3M syndrome. Genetic assessment revealed a novel homozygous frameshift c.418_419delAC (p.Thr140Cysfs*11) variant in the CUL7 gene and a previously reported pathogenic nonsense homozygous c.942C>A (p.Cys314Ter) variant in the ILDR1 gene. The parents were heterozygous for the same variant. Discussion: 3M syndrome should be considered in the differential diagnosis of patients with short stature and typical facial features even if in the presence of other inconsistent features such as developmental delay. In addition, it is important to take into account the co-occurrence of rare autosomal recessive genetic disorders especially in countries with a high consanguineous marriage rate.

Spondylo-meta-epiphyseal dysplasia (SMED), short limb-hand abnormal calcification type: Further expanding the mutational spectrum and dental findings of three new patients.

Genetic skeletal disorders are clinically and genetically heterogeneous group of disorders that affect the normal development, growth, and maintenance of the human skeleton. Spondylo-meta-epiphyseal dysplasia, short limb-abnormal calcification type (SMED-SL/AC; MIM# 271665) is a rare autosomal recessive genetic skeletal disorder characterized by distinctive facial features, disproportionate short stature, vertebral, metaphyseal, and epiphyseal abnormalities. This unique phenotype is caused by biallelic loss-of-function variants in Discoidin domain receptor 2 gene (DDR2, MIM# 191311). To date, only 10 pathogenic variants (six missense, two nonsense, one deletion, and one splice site) in DDR2 have been reported in patients with SMED-SL/AC. Dental anomalies related to skeletal dysplasia can include various abnormalities in the number, shape, and position of teeth in the jaw, as well as enamel hypoplasia and dentinogenesis imperfecta. Although abnormal dentition has previously been reported, orodental findings were described in only six patients with SMED-SL/AC. This study aimed to define the clinical, dental, radiological, and molecular findings of three new SMED-SL/AC patients from three unrelated families. Three DDR2 variants, two of which were novel, were detected with the aid of Sanger sequencing. Interestingly, one of the patients was diagnosed with Wilson's disease (WD) during the follow-up, a co-occurrence that has never been reported in patients with SMED-SL/AC so far.

Homozygous Missense Epithelial Cell Adhesion Molecule Variant in a Patient with Congenital Tufting Enteropathy and Literature Review.

Congenital diarrheal disorders (CDDs) with genetic etiology are uncommon hereditary intestinal diseases characterized by chronic, life-threatening, intractable watery diarrhea that starts in infancy. CDDs can be mechanistically divided into osmotic and secretory diarrhea. Congenital tufting enteropathy (CTE), also known as intestinal epithelial dysplasia, is a type of secretory CDD. CTE is a rare autosomal recessive enteropathy that presents with intractable neonatal-onset diarrhea, intestinal failure, severe malnutrition, and parenteral nutrition dependence. Villous atrophy of the intestinal epithelium, crypt hyperplasia, and irregularity of surface enterocytes are the specific pathological findings of CTE. The small intestine and occasionally the colonic mucosa include focal epithelial tufts. In 2008, Sivagnanam et al. discovered that mutations in the epithelial cell adhesion molecule (EpCAM, MIM# 185535) were the genetic cause of CTE (MIM# 613217). More than a hundred mutations have been reported to date. Furthermore, mutations in the serine peptidase inhibitor Kunitz type 2 (SPINT2, MIM# 605124) have been linked to syndromic CTE. In this study, we report the case of a 17-month-old male infant with congenital diarrhea. Despite extensive etiological workup, no etiology could be established before admission to our center. The patient died 15 hours after being admitted to our center in a metabolically decompensated state, probably due to a delay in admission and diagnosis. Molecular autopsy with exome sequencing revealed a previously reported homozygous missense variant, c.757G>A, in EpCAM, which was confirmed by histopathological examination.

A lethal and rare cause of arthrogryposis: Glyt1 encephalopathy.

Glycine encephalopathy with normal serum glycine (MIM #617301), also known as GLYT1 encephalopathy, is an extremely rare disorder caused by biallelic variants in SLC6A9 and characterised by facial dysmorphic features, skeletal findings including contractures, knee hyperextension, and joint dislocations and seizures. To date, only ten patients from five families have been reported and only two of them could survive until childhood. In this study, we report on a consanguineous Turkish couple with a history of six pregnancies with three habitual abortions and three postpartum exitus. While in three pregnancies the babies were born prematurely at 32nd gestational week by emergency ceserean section due to hydrops and fetal distress, the other pregnancy was medically terminated at 16th gestational week due to absent fetal heart activity. The product of all these three pregnancies exhibited similar phenotype including short neck, thoracic kyphosis, hypertrichosis, joint contractures and dislocations, hypertonia, knee hyperextension and facial dysmorphic features. Trio exome sequencing was performed prenatally during the last pregnancy and a novel VUS variant in SLC6A9 and a likely pathogenic variant in MTOR gene were detected. DNA isolation was performed from frozen muscle and adrenal tissue of previously autopsied fetuses with similar clinical features, and the same variants were confirmed in both of them. Our data suggest that SLC6A9 and MTOR variants may be responsible for this extremely lethal phenotype in this family.

Biallelic loss-of-function variants in EXOC6B are associated with impaired primary ciliogenesis and cause spondylo-epi-metaphyseal dysplasia with joint laxity type 3.

Spondylo-epi-metaphyseal dysplasias with joint laxity, type 3 (SEMDJL3) is a genetic skeletal disorder characterized by multiple joint dislocations, caused by biallelic pathogenic variants in the EXOC6B gene. Only four individuals from two families have been reported to have this condition to date. The molecular pathogenesis related to primary ciliogenesis has not been enumerated in subjects with SEMDJL3. In this study, we report two additional affected individuals from unrelated families with biallelic pathogenic variants, c.2122+15447_2197-59588del and c.401T>G in EXOC6B identified by exome sequencing. One of the affected individuals had an intellectual disability and central nervous system anomalies, including hydrocephalus, hypoplastic mesencephalon, and thin corpus callosum. Using the fibroblast cell lines, we demonstrate the primary evidence for the abrogation of exocytosis in an individual with SEMDLJ3 leading to impaired primary ciliogenesis. Osteogenesis differentiation and pathways related to the extracellular matrix were also found to be reduced. Additionally, we provide a review of the clinical and molecular profile of all the mutation-proven patients reported hitherto, thereby further characterizing SEMDJL3. SEMDJL3 with biallelic pathogenic variants in EXOC6B might represent yet another ciliopathy with central nervous system involvement and joint dislocations.

Diagnostic distribution and postnatal evaluation of prenatally detected short femur: A single center experience.

Genetic skeletal disorders (GSDs) are clinically and etiologically heterogeneous group of disorders caused by abnormal growth and development of bone and/or cartilaginous tissues. Timely and accurate diagnosis is essential for prevention of significant comorbidities. In this study demographic, parental, prenatal and natal characteristics, and postnatal diagnostic distribution along with follow-up processes of 104 individuals with the finding of "short femur" detected in routine prenatal ultrasonography were evaluated. Of 104 patients, 19 (18.2%) were medically terminated, 12 (11.6%) were deceased during follow-up and 73 (70.2%) were still under follow-up. Diagnostic distribution of 104 patients was as follows: 77 (74%) had GSD, eight (7.7%) had chromosomal disorder, seven (6.7%) were completely normal, and 12 (11.5%) had no definite diagnosis. Long-term follow up evaluation contributed to clinical diagnosis in four patients. When grouped according to Nosology and Classification of GSDs: 2019 revision, the most frequent (n = 30, 38.5%) group was "FGFR3 chondrodysplasia group", followed by "Type 2 collagen group" (n = 7, 9%), and "Osteogenesis imperfecta and decreased bone density group" (n = 5, 6.4%). The finding of prenatally detected "short femur" represents a group of diverse diagnosis with heterogeneous etiology. GSDs are the most common etiology among fetuses with short extremity.

Investigation of Genetic Causes in a Developmental Disorder: Oculoauriculovertebral Spectrum.

OBJECTIVE: Oculoauriculovertebral spectrum (OAVS) is a genetically and clinically heterogeneous disorder that occurs due to a developmental field defect of the first and second pharyngeal arches. Even though recent whole exome sequencing studies (WES) have led to identification of several genes associated with this spectrum in a subset of individuals, complete pathogenesis of OAVS remains unsolved. In this study, molecular genetic etiology of OAVS was systematically investigated. DESIGN/SETTING/PATIENTS: A cohort of 23 Turkish patients with OAVS, referred to Hacettepe University Hospital, Department of Pediatric Genetics from 2008 to 2018, was included in this study. Minimal diagnostic criteria for OAVS were considered as unilateral microtia or hemifacial microsomia with preauricular skin tag. The cohort was clinically reevaluated for craniofacial and extracranial findings. Molecular etiology was investigated using candidate gene sequencing following copy number variant (CNV) analysis. WES was also performed for 2 of the selected patients. RESULTS: Patients in the study cohort presented similar demographic and phenotypic characteristics to previously described patients in the literature except for a higher frequency of bilaterality, cardiac findings, and intellectual disability/developmental delay. CNV analysis revealed a possible genetic etiology for 3 patients (13%). Additional WES in 1 of the 2 patients uncovered a novel heterozygous nonsense variant in Elongation factor Tu GTP-binding domain-containing 2 (EFTUD2) causing mandibulofacial dysostosis with microcephaly (MFDM), which clinically overlaps with OAVS. CONCLUSION: Detailed clinical evaluation for any patient with OAVS is recommended due to a high rate of accompanying systemic findings. We further expand the existing genetic heterogeneity of OAVS by identifying several CNVs and a phenotypically overlapping disorder, MFDM.

Obstructive sleep apnea in children with Down syndrome: is it possible to predict severe apnea?

The objectives are to explore the demographic and polysomnographic features of children with Down syndrome and to determine the predictive factors associated with severe sleep apnea. A total of 81 children with Down syndrome referred for full-night polysomnography were analyzed. In addition, parental interviews were performed for each child. Data were available for 81 children, with a mean age of 4.8 years. Severe obstructive sleep apnea was determined in 53.1%. Age, sex, exposure to second-hand smoke, clinical findings, anthropometric features, and the presence of comorbidities were not predictors of severe obstructive sleep apnea. Children who were exposed to second-hand smoke had more sleep-related symptoms. Even in children without symptoms, the prevalence of severe obstructive sleep apnea was 40%. Moreover, 86% of parents had no previous information regarding possible sleep breathing disorders in their children. Clinically significant central apnea was present in 10 patients (12.3%).Conclusion: Our results demonstrate that severe obstructive sleep apnea is common in children with Down syndrome, even in children without a history of symptoms of sleep apnea. It is not possible to predict patients with severe apnea; thus, screening of children with Down syndrome beginning from young ages is very important. Central apneas could be a part of the spectrum of sleep abnormalities in Down syndrome.

Main Physical Features, Echocardiographic and Renal Ultrasonographic Findings of Turner Syndrome in 107 Pediatric Patients.

Turner syndrome (TS) is one of the most common malformation syndromes in females. A total number of 107 TS patients, diagnosed between 2000 and 2018, were evaluated for their phenotypic features, and cardiac and renal findings. The mean age of patients at admission was 10.08 ± 4.9 years (range, newborn to 18 years). Four different karyotype groups were encountered, and the most common findings in all groups were short stature, followed by cubitus valgus. Echocardiographic findings of 85 patients were available among which 63 (n = 63/85, 74.1%) were found to be normal. The most common cardiac anomaly was left ventricular outflow tract/aortic arch pathology detected in 9 patients (n = 9/22, 40.9%). Renal malformations were detected in 15 patients (n = 15/84, 17.9%) by renal ultrasonography, and horseshoe kidney was the most common renal malformation, followed by left multicystic dysplastic kidney. There was no significant difference in the frequency of renal malformation and cardiac anomalies among the 4different karyotype groups (χ2 exact test, p > 0.05). Compared with the literature, the frequency of renal anomalies was detected at a lower rate. Karyotype analysis should be carried out in all female patients with short stature, even if there are no associated phenotypic findings suggestive of TS. Since cardiac anomalies are frequently seen in TS patients and they represent a common cause of mortality, echocardiography should be carried out as soon as the definite diagnosis is established. Renal anomalies may be less frequent than cardiac anomalies; however, evaluation of TS patients with renal ultrasonography should be done at the time of diagnosis. Although renal ultrasonography can be used as the initial renal screening in TS patients, it may underestimate the frequency of renal malformation; hence, further management may be required.

Biallelic ITGB4 variants in familial pyloric atresia without epidermolysis bullosa: Report of two families with five siblings.

Pyloric atresia (PA) is a rare gastrointestinal anomaly that occurs either as an isolated lesion or in association with other congenital or hereditary anomalies. Familial occurrence of PA with epidermolysis bullosa (EB) has been well documented and variants in ITGA6, ITGB4, and PLEC are known to cause EB with PA. However, no gene variants have been defined in familial isolated PA. Five siblings with familial isolated PA are presented that suggest biallelic ITGB4 variants may underlie the development of PA without EB. Five siblings from two unrelated families with isolated PA were studied with exome sequencing (ES) to identify the genetic etiology in isolated familial cases. Exome sequencing was performed in one affected patient from each family. Validation and segregation studies were done by Sanger sequencing. Parents were first cousins in one family but there was no consanguinity in the other family. Type-2 PA was detected in both families and none of the probands had associated anomalies. All patients underwent successful gastroduodenostomy and have been under follow-up uneventfully. All patients had biallelic ITGB4 variants, c.2032G > T p.(Asp678Tyr) being a novel one. Biallelic ITGB4 variants may underlie the development of PA without associated EB. Further detection of variants in this gene may establish any possible genotype-phenotype correlations.

Sleep disordered breathing in patients with Prader willi syndrome: Impact of underlying genetic mechanism.

INTRODUCTION: Sleep-disordered breathing (SDB) is common in children with PWS. In the current study, we aimed to evaluate the severity of SDB in patients with PWS using polysomnography (PSG), and assess the effect of the underlying genetic mechanism on PSG parameters. METHODS: Children with PWS, referred to our sleep laboratory between March 2016 and January 2020 were enrolled. PSG parameters, demographic data, body mass index (BMI), and symptoms related to SDB were recorded. The effect of non-invasive ventilation strategies and the outcome of therapy on PSG parameters were evaluated. RESULTS: In our study, 64.5% of the patients had severe sleep apnea syndrome (total apnea hypopnea index (AHI) ≥10 events/hour). 22.6% had significantly high (>5 events/hour) central sleep apnea. Patients with a deletion had significantly lower initial and mean SaO2, longer sleep time SaO2 under 90%, oxygen desaturation % and total AHI when compared to those with uniparental disomy. PSG parameters were similar between patients who did or didn't receive growth hormone treatment. CONCLUSION: The majority of the PWS patients had severe sleep apnea syndrome characterized mainly by hypopneas which were accompanied by central apneas. There was a more severe impact on oxygen parameters and total AHI in patients with deletions.

Spondyloepimetaphyseal dysplasia EXTL3-deficient type: Long-term follow-up and review of the literature.

Spondyloepimetaphyseal dysplasia (SEMD) is a group of genetic skeletal disorders characterized by disproportionate short stature, and varying degrees of vertebral, epiphyseal, and metaphyseal involvement of the skeleton. According to the Nosology and classification of genetic skeletal disorders 2019 revision, more than 20 types of SEMD have been identified, and SEMD with immune deficiency, EXTL3 type is one of the newcomers. Affected individuals display variable skeletal abnormalities and neurodevelopmental findings. Liver and kidney cysts have also been reported frequently. Patients may exhibit varying degrees of immune deficiency as well. To date, only 14 patients from 9 unrelated families with SEMD with immune deficiency, EXTL3 type have been reported in the literature. We report a new patient who is currently 15 years old in whom cystic liver lesions were detected in the prenatal period. Disproportionate short stature, mild developmental delay and a T- NK+ B+ immunological profile were detected in the postnatal follow-up. Exome sequence analysis revealed a previously reported homozygous missense variant in exon 3 c.953C > T; p.(Pro318Leu) in EXTL3.

Two Siblings with Kaufman Oculocerebrofacial Syndrome Resembling Oculoauriculovertebral Spectrum.

Kaufman oculocerebrofacial syndrome is a rare autosomal recessive disorder which represents a phenotype mainly involving craniofacial and neurodevelopmental manifestations due to UBE3B gene mutations. The vast majority of the affected individuals exhibit microcephaly, eye abnormalities, and typical facial gestalt including blepharophimosis, ptosis, telecanthus, upslanting palpebral fissures, dysplastic ears, and micrognathia. We encountered 2 siblings in whom severe psychomotor delay, distinctive facial features, hearing loss, and respiratory distress were observed. Some clinical manifestations of the patients, including epibulbar dermoid, microtia, and multiple preauricular tags, were reminiscent of the oculoauriculovertebral spectrum. However, 2 affected siblings exhibited a similar clinical picture consisting of microcephaly, severe developmental and cognitive disabilities, failure to thrive, and dysmorphic features, which were not fully consistent with oculoauriculovertebral spectrum. Also, hypoplastic nails, considered as a core manifestation of Coffin-Siris syndrome, were present in our patients. Therefore, whole-exome sequencing was carried out in order to identify the underlying genetic alterations, contributing to the complex phenotype shared by the 2 siblings. A homozygous pathogenic mutation was found in both affected siblings in the UBE3B gene which caused Kaufman oculocerebrofacial syndrome. Kaufman oculocerebrofacial syndrome should be considered among the autosomal recessive causes of blepharophimosis-mental retardation syndromes, particularly in populations with a high rate of consanguineous marriages, even if there are dysmorphic facial features that are not typically associated with the phenotype.

Kohlschütter-Tönz Syndrome With a Novel ROGD1 Variant in 3 Individuals: A Rare Clinical Entity.

Kohlschütter-Tönz syndrome (OMIM 226750) is a rare disorder with autosomal recessive inheritance among epileptic encephalopathy syndromes. To date, only 31 Kohlschütter-Tönz syndrome families have been reported in the literature. Early-onset epilepsy, progressive global developmental delay, and amelogenesis imperfecta are the main components of the syndrome. Mutations in ROGDI (MIM 226750) and SLC13A5 (MIM 615905) are responsible for Kohlschütter-Tönz syndrome. Here, we report on the clinical and molecular characteristics of 3 individuals from 2 families, all harboring the same homozygous novel deleterious variant in ROGD1, along with a long-term follow-up and review of the literature. Although the phenotypic features are almost consistent in Kohlschütter-Tönz syndrome, overlooking dental findings and diverse degrees of variability in clinical findings makes diagnosis challenging occasionally. Because there is a limited number of reported patients, identification of new patients and delineation of clinical and molecular findings will increase the awareness of clinicians and enable establishing genotype-phenotype correlations.

Natural history of TRPV4-Related disorders: From skeletal dysplasia to neuromuscular phenotype.

TRPV4-related disorders constitute a broad spectrum of clinical phenotypes including several genetic skeletal and neuromuscular disorders, in which clinical variability and somewhat overlapping features are present. These disorders have previously been considered to be clinically distinct phenotypes before their molecular basis was discovered. However, with the identification of TRPV4 variants in the etiology, they are referred as TRPV4-related disorders (TRPV4-pathies), and are now mainly grouped into skeletal dysplasias and neuromuscular disorders. The skeletal dysplasia group includes metatropic dysplasia, parastremmatic dysplasia, spondyloepiphyseal dysplasia Maroteaux type, spondylometaphyseal dysplasia Kozlowski type, autosomal dominant brachyolmia, and familial digital arthropathy-brachydactyly, whereas the neuromuscular group includes congenital distal spinal muscular atrophy (SMA), scapuloperoneal SMA and Charcot-Marie-Tooth neuropathy type 2C with common manifestations of peripheral neuropathy, joint contractures, and respiratory system involvement. Apart from familial digital arthropathy-brachydactyly, skeletal dysplasia associated with TRPV4 pathogenic variants share some clinical features such as short stature with short trunk, spinal and pelvic changes with varying degrees of long bone involvement. Of note, there is considerable phenotypic overlap within and between both groups. Herein, we report on the clinical and molecular spectrum of 11 patients from six different families diagnosed with TRPV4-related disorders. This study yet represents the largest cohort of patients with TRPV4 variants from a single center in Turkey.

Further expanding the mutational spectrum of brain abnormalities, neurodegeneration, and dysosteosclerosis: A rare disorder with neurologic regression and skeletal features.

Colony stimulating factor 1 receptor (CSF1R, MIM# 164770) encodes a tyrosine-kinase receptor playing an important role in development of osteoclasts and microglia. Heterozygous CSF1R variants have been known to cause hereditary diffuse leukoencephalopathy with spheroids (HDLS, MIM# 221820), an adult-onset leukoencephalopathy characterized by loss of motor functions and cognitive decline. Recently, a new phenotype characterized by brain abnormalities, neurodegeneration, and dysosteosclerosis (BANDDOS) with biallelic CSF1R pathogenic variants in the etiology has been described. BANDDOS differs from HDLS by early-onset neurodegenerative changes with additional structural brain abnormalities and skeletal findings resembling dysosteosclerosis (DOS). Described skeletal findings of the disease are highly variable ranging from absence of a skeletal phenotype and milder Pyle disease-like to osteopetrosis and DOS. To date, only a few patients carrying biallelic CSF1R variants have been reported. In this clinical report, we describe three siblings with variable skeletal findings along with neurological symptoms ranging from mild to severe in whom exome sequencing revealed a novel homozygous splice site variant in canonical splice donor site of intron 21 adjacent to an exon, which encoding part of kinase domain of CSF1R along with a review of the literature.