American Journal of Medical Genetics Part A最新文献

RASopathies are clinically overlapping neurodevelopmental syndromes resulting from germline mutations in genes involved in the rat sarcoma/mitogen-activated protein kinases (RAS/MAPK) pathway. Historically, RASopathies have been described by clinical phenotypes, such as Noonan syndrome and Neurofibromatosis type I. There is emerging evidence of the association between Noonan syndrome spectrum disorders (NSSD) and systemic lupus erythematosus (SLE). Here, we present an SLE patient diagnosed with SOS1-associated Noonan Syndrome (c.806 T>C; p.Met269Thr) as part of a research study. Reviewing the literature, we identified further 16 cases of NSSD associated with SLE. Nine out of 16 cases (56%) had a confirmed molecular diagnosis, with pathogenic missense variants identified in KRAS, PTPN11, and SHOC2 genes, the majority in the last. Variants in SHOC2 are the cause of only a small proportion of all presentations of NSSD. Our case represents the first reported case of SLE in a patient with a SOS1 pathogenic variant. Compared to the general SLE population, SLE in the presence of NSSD develops at a younger age, with a similar prevalence among females and males, suggesting a contribution of the RAS/MAPK pathway in the development of SLE.

Missense variants in the KCNQ2 gene can cause developmental and epileptic encephalopathy (DEE). While most KCNQ2-DEE cases are attributed to loss-of-function (LOF) mutations, gain-of-function (GOF) mutations have also been implicated in the disorder. This study describes the clinical features of a DEE patient with a KCNQ2 mutation in the voltage-sensing domain (VSD) and analyzes the variant's electrophysiological properties. Whole-exome sequencing was performed to identify the genetic variant. Whole-cell patch-clamp electrophysiology was used to characterize the functional effects of the mutant channel, both alone and in combination with KCNQ3 subunits at a 1:1:2 ratio to mimic the patient's allele dosage. The effect of amitriptyline (AMI) on channel activity was also evaluated. A three-year-old female with early-onset epileptic encephalopathy presented with intractable seizures, developmental regression, microcephaly, transient thyroid dysfunction, and a mixed EEG pattern of hypsarrhythmia and intermittent burst-suppression. A de novo KCNQ2 variant (c.401T>A, p.Ile134Asn) located in the conserved S2 transmembrane domain was identified and classified as likely pathogenic. Electrophysiological analysis showed that the KCNQ2-I134N mutation caused a hyperpolarizing shift in voltage-dependent activation and significantly increased current density, indicating a GOF effect. This GOF phenotype persisted when the mutant subunit was co-expressed with KCNQ3 and under a transfection ratio mimicking the patient's genotype. The hyperactivity of the mutant channel was effectively suppressed by amitriptyline. We report a novel GOF variant (I134N) in the KCNQ2 gene associated with DEE. The KCNQ blocker amitriptyline effectively suppressed mutant channel hyperactivity, suggesting its potential as a targeted therapeutic option for patients with this pathogenic variant.

Erdheim-Chester disease (ECD) is a rare, systemic, and potentially malignant non-Langerhans cell histiocytosis characterized by the infiltration of foamy histiocytes into multiple organ systems. The diagnosis of ECD is often complicated and time-consuming due to its rarity and heterogeneous presentation. A 39-year-old female presented with a progressively enlarging yellowish plaque measuring 5 × 2 cm on left periorbital skin over the past 2 years. Besides, the patient had bilateral lower extremity pain persisting for 1.5 years, significantly affecting her mobility and quality of life. Histological examination of skin biopsies revealed frequent Touton giant cells, bland-appearing histiocytes characterized by abundant foamy (xanthomatous) cytoplasm in the dermis, which were positive for CD68, Factor XIIIa, and BRAF; negative for CD1a and S100. In bone marrow biopsy, histiocytic cells were positively stained with CD68, Factor XIIIa, and CD14, and negatively stained for CD1a, Langerin, and S100. Positron emission tomography/computed tomography imaging revealed pathological 18-fluoro-2-deoxyglucose uptake in the bone marrow and widespread sclerotic bone lesions on the bilateral lower extremity. BRAF sequencing determined a BRAFV600E mutation. The patient was diagnosed with ECD, and vemurafenib was initiated. After 6 months of treatment, significant improvements were observed in both bone pain and the size and discoloration of the yellowish plaque. In conclusion, our case highlights that the primary diagnostic clue for ECD may be a single yellowish plaque, which requires further investigation in relation to other systemic symptoms. Vemurafenib treatment may lead to regression of systemic symptoms and cutaneous yellowish plaques associated with ECD carrying a BRAF mutation.

The cover image is based on the article Identification of a Non-Coding Causative Variant Underlying Warsaw Breakage Syndrome Using Long-Read Based Genomic Sequencing and Transcriptome Analysis by Makenna DuBois et al., https://doi.org/10.1002/ajmg.a.64252.

Marfan syndrome (MFS) is a rare connective tissue disorder characterized by involvement of the cardiovascular, ocular, and musculoskeletal systems. Pathogenic variants in FBN1 cause most of the MFS cases; however, intellectual disability (ID) is rarely observed. A non-consanguineous Pakistani family with four affected individuals was recruited. Physical examinations, echocardiography, and doppler ultrasound were performed as part of the clinical assessment. Exome sequencing was conducted on the index patient, and Sanger sequencing was performed for the entire family. ID was the primary symptom in all the affected individuals. A detailed examination showed that all affected individuals and their affected mother were tall, had long limbs, craniofacial abnormalities, and exhibited low IQ, aggressive, and hyperactive behaviors. Heart defects, such as atrial septal defects and pulmonary hypertension, were observed in one affected individual and her mother. Genetic analysis identified two rare missense variants in FBN1, c.1552G>A (p.Gly518Arg) and c.3046A>G (p.Thr1016Ala), both predicted to be deleterious. The p.Gly518Arg variant is predicted to be likely pathogenic, while the p.Thr1016Ala variant is of uncertain significance. Notably, these variants were found in two affected individuals in a compound heterozygous state, correlating with more severe symptoms. Each variant alone, seen in the two patients, is associated with milder symptoms, indicating incomplete penetrance. In conclusion, this study identified rare heterozygous missense variants in FBN1, suggesting a potential connection between neurodevelopmental outcomes and variants in FBN1. However, further research is needed to clarify the role of FBN1 in ID.

Mosaicism is relatively common in Tuberous Sclerosis Complex (TSC) but can be difficult to detect using routine diagnostic tests, particularly when the variant allele frequency (VAF) is low. We describe two cases of mosaic TSC diagnosed using an ultra-deep sequencing approach in multiple tissues and review the literature about this topic in order to discuss new diagnostic paradigms. In the first case, further testing was prompted by the presence of angiomyolipomas in the otherwise unaffected 51-year-old father of a woman diagnosed with TSC2; the familial pathogenic variant was present with a very low VAF in angiomyolipoma tissue and peripheral blood. The second case, a 17-year-old boy diagnosed with infantile myofibromatosis, presented dermatological and brain MRI findings suggestive of TSC; a TSC1 pathogenic variant was first identified on DNA extracted from angiofibroma biopsy, and then confirmed on non-lesional skin, peripheral blood, and saliva. The identification of the causative TSC1/2 variant is crucial to provide appropriate management and genetic counseling for family planning. Most mosaic individuals in the literature have cutaneous features of TSC; in the presence of an accessible lesion, we recommend considering a tissue biopsy to have a higher chance of identifying a low-level mosaicism.

Hereditary sensory and autonomic neuropathy type IV (HSAN4) is a rare neurological disorder characterized by anhidrosis and congenital insensitivity to pain caused by biallelic pathogenic variants in NTRK1. The condition develops because of dorsal root and autonomic ganglion neurodegeneration, which ultimately results in reduced sensation and autonomic neurological dysfunction. We ascertained several neuropathic patients and performed genetic testing using gene panels and exome sequencing (ES). Genetic variants were confirmed by Sanger sequencing. Thirteen families, each with a single affected individual, participated in this study. Genetic testing revealed that all patients carried disease-causing variants in NTRK1. We identified seven different variants within our cohort, including two novel variants (c.1922T>C:p.Leu641Pro and c.1071_1072insTGCC:p.Asn358Cysfs*45). While some variants suggest a possible founder effect, the identification of new variants reflects the genetic diversity within the Saudi population. In addition to the cardinal clinical feature of HSAN4, patients exhibited various other symptoms like motor difficulties, microcephaly, recurrent hip dislocation, dystrophic nails, hypotrichosis, and various dysmorphic features. This study provides clinical information on a large number of patients, updates the prevalence and epidemiologic data in our population, and further expands the understanding of the disease's genetic and clinical spectrum within a highly consanguineous population.

The KDM2B-related neurodevelopmental disorder is a recently identified Mendelian disorder of the epigenetic machinery associated with pathogenic variants in KDM2B. Global developmental delay, intellectual disability, congenital anomalies, and systemic manifestations characterize the disorder. Variants in KDM2B that primarily affect the CxxC DNA-binding domain are strongly linked to a specific epigenetic signature. We present three children with KDM2B-related neurodevelopmental disorder, each with a heterozygous variant in the CxxC domain of KDM2B. Patient 1 is a 2-year-old boy with developmental delay, solitary kidney, atrial septal defect, feeding difficulties, hemangiomas, and myopic astigmatism. Patient 2 is a 2-year-old girl with global developmental delay, hip dysplasia, feeding difficulties, hemangiomas, and myopic astigmatism. Patient 3 is a 5-year-old girl with autism, developmental delay, atrial septal defect, and ventricular septal defect, hypertrichosis, atopic dermatitis, and myopic astigmatism. Genetic analysis revealed a variant in KDM2B in each patient. Targeted methylation analysis for the epigenetic signature associated with the KDM2B-related syndrome revealed an abnormal methylation pattern consistent with a positive epigenetic signature of the disorder in individuals 2 and 3. These results provided supportive functional evidence for KDM2B-related neurodevelopmental disorder in the context of the clinical findings and KDM2B variants. Our findings emphasize the value of integrating genomic and epigenomic analyses for variant interpretation. This case series reinforces the consistent phenotype of KDM2B-related neurodevelopmental disorder and highlights ocular and dermatologic manifestations as recurring features in affected individuals.