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PURPOSE: To review the molecular genetics of Axenfeld-Rieger syndrome and related phenotypes and to discuss how this information might affect the way that we classify these disorders. METHODS: A review of historical and recent literature on Axenfeld-Rieger syndrome and related disorders. The review includes clinical and molecular genetic literature relevant to these phenotypes. RESULTS: Three chromosomal loci have recently been demonstrated to link to Axenfeld-Rieger syndrome and related phenotypes. These loci are on chromosomes 4q25, 6p25, and 13q14. The genes at chromosomes 4q25 and 6p25 have been identified as PITX2 and FKHL7, respectively. Mutations in these genes can cause a wide variety of phenotypes that share features with Axenfeld-Rieger syndrome. Axenfeld anomaly, Rieger anomaly, Rieger syndrome, iridogoniodysgenesis anomaly, iridogoniodysgenesis syndrome, iris hypoplasia, and familial glaucoma iridogoniodysplasia all have sufficient genotypic and phenotypic overlap that they should be considered one condition. CONCLUSIONS: Axenfeld-Rieger syndrome is a term that can be used to describe a variety of overlapping phenotypes. To date, at least three known genetic loci can cause these disorders. The single most important feature of these phenotypes is that they confer a 50% or greater risk of developing glaucoma. Currently there is a fairly arbitrary grouping of disorders into small categories. Considering all of these phenotypes under the heading of Axenfeld-Rieger syndrome will allow easier communication between clinicians and scientists and eliminate arbitrary and confusing subclassification.
BACKGROUND: Overlapping phenotypes including LHON, MELAS, and Leigh syndrome have recently been associated with numerous mtDNA point mutations in the ND5 gene of complex I, now considered a mutational hot spot. OBJECTIVE: To identify the mtDNA defect in a family with a prevalent ocular phenotype, including LHON-like optic neuropathy, retinopathy, and cataract, but characterised also by strokes, early deaths, and miscarriages on the maternal line. RESULTS: Sequencing of the entire mitochondrial genome from the proband's muscle DNA identified the heteroplasmic 13042G-->A transition, which was previously described only once in a patient with a different mitochondrial disease. This mutation fulfils the major pathogenic criteria, inducing an amino acid change (A236T) at an invariant position in a highly conserved domain of the ND5 gene. Phosphorus magnetic resonance spectroscopy in the proband disclosed an in vivo brain and skeletal muscle energy metabolism deficit. CONCLUSIONS: These findings conclusively establish the pathogenic role of the 13042G-->A mutation and underscore its variable clinical expression.
The growth and differentiation factor transforming growth factor-beta2 (TGFbeta2) is thought to play important roles in multiple developmental processes. Targeted disruption of the TGFbeta2 gene was undertaken to determine its essential role in vivo. TGFbeta2-null mice exhibit perinatal mortality and a wide range of developmental defects for a single gene disruption. These include cardiac, lung, craniofacial, limb, spinal column, eye, inner ear and urogenital defects. The developmental processes most commonly involved in the affected tissues include epithelial-mesenchymal interactions, cell growth, extracellular matrix production and tissue remodeling. In addition, many affected tissues have neural crest-derived components and simulate neural crest deficiencies. There is no phenotypic overlap with TGFbeta1- and TGFbeta3-null mice indicating numerous non-compensated functions between the TGFbeta isoforms.
OBJECTIVE: To determine the clinical phenotypes in carriers with probable disease-causing sequence variations in 1 of 6 genes established to cause Leber congenital amaurosis (LCA). DESIGN: Observational prospective comparative study. PARTICIPANTS: Thirty carriers with various probable disease-causing sequence variations in 1 of 6 genes known to cause LCA. METHODS: After the establishment of various disease-causing sequence variations in 37 (33.6%) of 110 patients with LCA, we examined a number of carriers who were either parents or offspring and who were willing to participate in our study. Evaluations included assessment of visual acuity, slit-lamp biomicroscopy, dilated fundus examination, and full-field electroretinogram (ERG) measurements. MAIN OUTCOME MEASURES: Dilated fundus examination and full-field ERGs. RESULTS: Of the 30 carriers with probable disease-causing sequence variations for LCA, 5 (16.7%) carriers had an AIPL1 variation, 4 (13.3%) CRB1, 0 (0%) CRX, 5 (16.7%) GUCY2D, 9 (30%) RPE65, and 7 (23.3%) carriers had a RPGRIP1 variation. Twenty-nine (96.7%) carriers had 20/20 or better visual acuity in their better seeing eye with correction. Drusenlike deposits were more selectively observed in carriers with mutations in the AIPL1, CRB1, RPE65, and RPGRIP1 genes, whereas mild peripheral chorioretinal atrophy was only observed in AIPL1 and RPE65 carriers. A reduced dark-adapted isolated rod ERG response and/or maximal combined cone and rod response was recorded in carriers with mutations in the AIPL1, GUCY2D, and RPGRIP1 genes. A reduced light-adapted ERG response to a single-flash and/or 32-Hz flicker was recorded in carriers with mutations in the AIPL1, CRB1, GUCY2D, and RPGRIP1 genes. Overall, our cohort of LCA carriers did not describe significant subjective visual difficulties, including nyctalopia and/or photosensitivity. CONCLUSIONS: The variation of phenotypic expression in carriers among 5 LCA genotypes indicates that there is considerable phenotypic overlap. However, phenotypic trends were noted in carriers' fundus findings and ERG responses for each genetic subtype. Observations of phenotypic associations with specific disease-causing sequence variations in carriers have potential practical value for molecular screening strategies of patients with LCA.
Disorders that include polydactyly as a manifestation are diverse and numerous. Cataloging these disorders by phenotype and genotype demonstrates numerous overlapping phenotypes, genetic heterogeneity of phenotypes, and distinct phenotypes generated from mutations in single genes. To assess these issues, a list of disorders with polydactyly has been compiled from several sources. Among 119 disorders, 39 disorders are associated with mutations in genes, and among these, genotypic and phenotypic overlap is demonstrated. These issues highlight the need for a diagnostic system that catalogs both genotype and phenotype. Published 2002 Wiley-Liss, Inc.
Cornelia de Lange syndrome (CdLS; OMIM 122470) is a dominantly inherited disorder characterized by multisystem involvement, cognitive delay, limb defects, and characteristic facial features. Recently, mutations in NIPBL have been found in approximately 50% of individuals with CdLS. Numerous chromosomal rearrangements have been reported in individuals with CdLS. These rearrangements may be causative of a CdLS phenotype, result in a phenocopy, or be unrelated to the observed phenotype. We describe two half siblings with a der(3)t(3;12)(p25.3;p13.3) chromosomal rearrangement, clinical features resembling CdLS, and phenotypic overlap with the del(3)(p25) phenotype. Region-specific BAC probes were used to fine-map the breakpoint region by fluorescence in situ hybridization (FISH). FISH analysis places the chromosome 3 breakpoint distal to RP11-115G3 on 3p25.3; the chromosome 12 breakpoint is distal to BAC RP11-88D16 on 12p13.3. A review of published cases of terminal 3p deletions and terminal 12p duplications indicates that the findings in these siblings are consistent with the del(3)(p25) phenotype. Given the phenotypic overlap with CdLS, we have reviewed the reported cases of chromosomal rearrangements involved in CdLS to better elucidate other potential loci that could harbor additional CdLS genes. Additionally, to identify chromosome rearrangements, genome-wide array comparative genomic hybridization (CGH) was performed on eight individuals with typical CdLS and without identifiable deletion or mutation of NIPBL. No pathologic rearrangements were identified.
BACKGROUND: DNASE1L3 deficiency is a rare monogenic cause of lupus and lupus-like autoimmunity resulting from impaired extracellular DNA clearance and sustained immune activation. Although most reported patients present with early-onset systemic lupus erythematosus (SLE), emerging evidence suggests broader phenotypic variability, including vasculitic and overlap manifestations. Whether these presentations represent distinct clinical entities or a continuum of DNASE1L3-associated immune dysregulation remains unclear. We aimed to define the clinical spectrum of DNASE1L3 deficiency and examine the relationship between recurrent pathogenic variants and disease severity. METHODS: We conducted a combined pediatric case series and systematic literature review. Four children with genetically confirmed biallelic DNASE1L3 variants followed at a tertiary pediatric rheumatology centre were retrospectively analysed for clinical, immunological, genetic, treatment, and outcome data. In parallel, a systematic search of PubMed/MEDLINE, Scopus, and Web of Science identified previously reported patients with confirmed biallelic pathogenic or likely pathogenic DNASE1L3 variants and extractable patient-level clinical data. To facilitate cross-case comparison, we applied an exploratory three-tier descriptive framework reflecting increasing disease severity: vasculitic or organ-limited disease (G1), systemic lupus or overlap phenotypes without irreversible organ damage (G2), and severe systemic organ-damaging disease (G3). The assigned grades were descriptive rather than permanent categories, as some patients may meet the criteria for a higher grade if broader systemic manifestations or irreversible organ damage develop during follow-up. FINDINGS: Fifteen reports provided extractable patient-level data, corresponding to 45 unique previously reported patients after accounting for known or probable overlapping reports. Combined with four patients from our centre, the analysis included 49 genetically confirmed individuals. SLE-dominant disease was the most frequent phenotype (27 [60%] of 45), followed by hypocomplementaemic urticarial vasculitis/HUVS-dominant disease (10 [22.2%]) and overlap phenotypes (8 [17.8%]). Renal involvement was reported in 30 (66.7%) of 45 patients, and disease onset occurred by age 3 years in 20 (44.4%). Persistent hypocomplementemia affecting C3 and C4 was frequently reported across the spectrum. Recurrent DNASE1L3 variants were observed across multiple phenotypic and severity grades. Variants such as p.Asn191Ser and p.Thr97Ilefs*2 occurred in patients spanning organ-limited vasculitic disease, lupus overlap phenotypes, and severe multisystem lupus with major organ involvement. CONCLUSION: DNASE1L3 deficiency was associated with a broad clinical spectrum of immune-mediated disease rather than a single clinicopathological entity. The occurrence of identical pathogenic variants across distinct phenotypic and severity states argues against a simple genotype-phenotype model and suggests that additional modifiers influence disease expression.
IMPORTANCE: Severe cutaneous adverse reactions (SCARs), including Stevens-Johnson syndrome/toxic epidermal necrolysis (SJS-TEN), drug reaction with eosinophilia and systemic symptoms (DRESS), acute generalized exanthematous pustulosis (AGEP), and generalized bullous fixed drug eruption (GBFDE), are rare but life-threatening drug hypersensitivity syndromes. Due to their low incidence and diagnostic complexity, large-scale characterization of SCAR is challenging. OBJECTIVE: To characterize the demographics, causative agents, trends, latency, and phenotypic overlap of SCAR using a large-scale, sanitized pharmacovigilance dataset from FAERS (FDA Adverse Event Reporting System). DESIGN: Cross-sectional study of spontaneous adverse event reports. Cases were drawn from the U.S. Food and Drug Administration Adverse Event Reporting System (FDA FAERS) from January 2004 to December 2023 and subjected to sanitization and deduplication. Disproportionality analysis was used to characterize causative agents. Machine learning (random forest classifiers) was used to analyze predictors of drug latency and mortality. SETTING: Global pharmacovigilance reports submitted to FAERS. PARTICIPANTS: A total of 56,683 deduplicated SCAR reports were identified, representing 0.33% of reports during the study period. EXPOSURES: Suspected causative drugs, including both small molecules and biologics. MAIN OUTCOMES AND MEASURES: Main outcomes included the frequency and distribution of SCAR syndromes, reporting trends over time, latency from drug start to reaction onset, drug-specific disproportionality (PRR, ROR, IC), and co-reporting between SCAR types and related conditions. RESULTS: A total of 56,683 unique SCAR reports were identified, including SJS-TEN (28,871), DRESS (22,444), AGEP (6,183), and GBFDE (150). We identified 237 drugs with significant disproportionality for SCAR overall. Co-reporting between SCARs was significantly enriched (p < 1e-200), suggesting overlapping phenotypes. Latency varied by drug and syndrome (median: GBFDE 3 days, AGEP 4 days, SJS-TEN 12 days, DRESS 20 days). CONCLUSIONS AND RELEVANCE: SCAR syndromes display distinct but overlapping phenotypes, with variable latency and diverse causative agents. These findings, based on the largest SCAR dataset to date, highlight the need for improved classification frameworks and molecular validation. Large-scale pharmacovigilance, integrated with genomic and histopathologic data, will be critical to improving diagnosis, mechanistic understanding, and clinical management of SCAR.
This report describes a child having the syndrome of overlapping phenotypic features of mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) and mitochondrial neurogastrointestinal encephalopathy syndrome (MNGIE). Mitochondrial DNA analysis revealed a point mutation at position A3243G, whereas activity of thymidine phosphorylase and its corresponding gene analysis were normal. The most striking feature of this case was paralysis of one segment of the terminal ileum observed on laparotomy. The electron microscopic findings of the resected ileum and colon by limited right hemicolectomy disclosed accumulation of numerous enlarged mitochondria with ill-defined cristae which were similar to mitochondria reported in three previous MELAS cases and one MNGIE case with intestinal dysmotility. We emphasize that the MELAS and MNGIE phenotypes overlapped in this case and that the mechanism of acute ileus in MELAS was associated with functional paralysis of the intestine.
Stickler and Marshall syndromes are dominantly inherited chondrodysplasias characterized by midfacial hypoplasia, high myopia, and sensorineural-hearing deficit. Since the characteristics of these syndromes overlap, it has been argued whether they are distinct entities or different manifestations of a single syndrome. Several mutations causing Stickler syndrome have been found in the COL2A1 gene, and one mutation causing Stickler syndrome and one causing Marshall syndrome have been detected in the COL11A1 gene. We characterize here the genomic structure of the COL11A1 gene. Screening of patients with Stickler, Stickler-like, or Marshall syndrome pointed to 23 novel mutations. Genotypic-phenotypic comparison revealed an association between the Marshall syndrome phenotype and splicing mutations of 54-bp exons in the C-terminal region of the COL11A1 gene. Null-allele mutations in the COL2A1 gene led to a typical phenotype of Stickler syndrome. Some patients, however, presented with phenotypes of both Marshall and Stickler syndromes.
We describe a Bedouin boy with multiple congenital anomalies/mental retardation (MCA/MR). He has frontal bossing, ridged metopic suture, bilateral ptosis, right squint, depressed nasal bridge, small nose, anteverted nostrils, lobulated tongue, polydactyly of both hands, microphallus, hypoplastic scrotum, microtestes, dysgenesis of corpus callosum, and a Dandy-Walker variant. This phenotype overlaps both the Varadi-Papp syndrome (OFD VI) and Opitz trigonocephaly (C syndrome). This phenotypic overlap is discussed in light of the concept of splitting and lumping in genetic diseases.
It has long been recognized that there is phenotypic overlap between Rett syndrome (RS) and autism. Advances in our clinical and genetic understanding of RS over the past decade have made clear that the cause and course of RS and autism are distinct (except perhaps in a few cases). Despite this, further delineation of the phenotypic overlap between RS and autism is warranted to enhance clinical decision-making and to further understanding of neuropathological development in both disorders. The present study measured autistic symptoms using the Autism Behavior Checklist (ABC) in a sample of girls with RS and a comparison group of girls with severe and profound mental retardation (SMR). Controlling for developmental level and motor ability, girls with RS scored more highly than those with SMR on the Sensory and Relating subscales. In contrast, there were no group differences on the Body and Object use, Language and Social and Self-help subscales. Further work on the characterisation of the behavioral phenotype of genetic disorders such as RS and autism may aid in identifying the neuropathogenic processes that lead from gene-to-brain-to-behavior.
Among the ectodermal dysplasias, there are several examples of overlapping phenotypes in disorders that are considered distinct. We report a 5-year-old boy born to nonconsanguineous parents and presenting with ectodermal dysplasia, ankyloblepharon filiforme adnatum, and bilateral choanal atresia consistent with the diagnosis of AEC syndrome. We compare the findings in our patient with the previous reported cases and discuss the overlapping phenotype of this disorder with CHAND syndrome.
Angelman syndrome (AS) is a neurodevelopmental disorder characterised by severe mental retardation, absent speech, ataxia, sociable affect, and dysmorphic facial features. Eighty five percent of patients with AS have an identifiable genetic abnormality of chromosome 15q11-13. Mutations within the X linked MECP2 gene have been identified in patients with Rett syndrome (RTT), a neurodevelopmental disorder which affects females almost exclusively and which shares phenotypic overlap with AS. RTT is usually associated with normal development in infancy followed by loss of acquired skills and evolution of characteristic hand wringing movements and episodes of hyperventilation.A panel of 25 female and 22 male patients with a clinical diagnosis of AS and no molecular abnormality of 15q11-13 were screened for MECP2 mutations and these were identified in four females and one male. Following the diagnosis, it was possible to elicit a history of regression in three of these patients, who by then were showing features suggestive of Rett syndrome. In the remaining two subjects the clinical phenotype was still considered to be Angelman-like. These findings illustrate the phenotypic overlap between the two conditions and suggest that screening for MECP2 mutations should be considered in AS patients without a demonstrable molecular or cytogenetic abnormality of 15q11-13. Since MECP2 mutations almost always occur de novo, their identification will substantially affect genetic counselling for the families concerned.
Gitelman syndrome is a renal disorder characterized by hypokalemia, hypomagnesemia, metabolic alkalosis and hypocalciuria due to the defective tubular reabsorption of magnesium and potassium. This disease is caused by mutations of thiazide-sensitive Na-Cl cotransporter (TSC) gene. Gitelman syndrome is usually distinguished from Bartter syndrome by the presence of both hypomagnesemia and hypocalciuria. However, a phenotypic overlap is sometimes observed. We encountered two sporadic Japanese patients with Gitelman syndrome and analyzed their TSC gene. These patients were diagnosed as Gitelman syndrome by the typical clinical findings and biochemical abnormalities, such as mild muscular weakness, periodic paralysis, tetany, metabolic alkalosis, hypomagnesemia and hypocalciuria. In patient 1, a novel two base deletion (del TG at nucleotide 731 and 732) in exon 5 and a two base deletion (del TT at nucleotide 2543 and 2544) in exon 21 previously reported in a Japanese patient were identified. The patient 2 had a missense mutation (L623P), that was also identified in Japanese patients, and a novel in-frame 18 base insertion in exon 6 as a heterozygous state. Family analysis of two patients confirmed an autosomal recessive inheritance. In conclusion, we add two new mutations of the TSC gene in Japanese patients with Gitelman syndrome. Because the differential diagnosis between Bartter syndrome and Gitelman syndrome is sometimes difficult, molecular analysis would be a useful diagnostic tool, particularly in unusual cases with phenotypic overlapping.