Clinical, genetic and structural delineation of RPL13-related spondyloepimetaphyseal dysplasia suggest extra-ribosomal functions of eL13

Spondyloepimetaphyseal dysplasia with severe short stature, RPL13-related (SEMD-RPL13), MIM#618728), is a rare autosomal dominant disorder characterized by short stature and skeletal changes such as mild spondylar and epimetaphyseal dysplasia affecting primarily the lower limbs. The genetic cause was first reported in 2019 by Le Caignec et al., and six disease-causing variants in the gene coding for a ribosomal protein, RPL13 (NM_000977.3) have been identified to date. This study presents clinical and radiographic data from 12 affected individuals aged 2-64 years from seven unrelated families, showing highly variable manifestations. The affected individuals showed a range from mild to severe short stature, retaining the same radiographic pattern of spondylar- and epi-metaphyseal dysplasia, but with varying severity of the hip and knee deformities. Two new missense variants, c.548 G>A, p.(Arg183His) and c.569 G>T, p.(Arg190Leu), and a previously known splice variant c.477+1G>A were identified, confirming mutational clustering in a highly specific RNA binding motif. Structural analysis and interpretation of the variants' impact on the protein suggests that disruption of extra-ribosomal functions of the protein through binding of mRNA may play a role in the skeletal phenotype of SEMD-RPL13. In addition, we present gonadal and somatic mosaicism for the condition.

Genome sequencing is a sensitive first-line test to diagnose individuals with intellectual disability

PURPOSE

Individuals with intellectual disability (ID) and/or neurodevelopment disorders (NDDs) are currently investigated with several different approaches in clinical genetic diagnostics.

METHODS

We compared the results from 3 diagnostic pipelines in patients with ID/NDD: genome sequencing (GS) first (N = 100), GS as a secondary test (N = 129), or chromosomal microarray (CMA) with or without FMR1 analysis (N = 421).

RESULTS

The diagnostic yield was 35% (GS-first), 26% (GS as a secondary test), and 11% (CMA/FMR1). Notably, the age of diagnosis was delayed by 1 year when GS was performed as a secondary test and the cost per diagnosed individual was 36% lower with GS first than with CMA/FMR1. Furthermore, 91% of those with a negative result after CMA/FMR1 analysis (338 individuals) have not yet been referred for additional genetic testing and remain undiagnosed.

CONCLUSION

Our findings strongly suggest that genome analysis outperforms other testing strategies and should replace traditional CMA and FMR1 analysis as a first-line genetic test in individuals with ID/NDD. GS is a sensitive, time- and cost-effective method that results in a confirmed molecular diagnosis in 35% of all referred patients.

Expanding the mutation and phenotype spectrum of MYH3-associated skeletal disorders

Pathogenic variants in MYH3 cause distal arthrogryposis type 2A and type 2B3 as well as contractures, pterygia and spondylocarpotarsal fusion syndromes types 1A and 1B. These disorders are ultra-rare and their natural course and phenotypic variability are not well described. In this study, we summarize the clinical features and genetic findings of 17 patients from 10 unrelated families with vertebral malformations caused by dominant or recessive pathogenic variants in MYH3. Twelve novel pathogenic variants in MYH3 (NM_002470.4) were identified: three of them were de novo or inherited in autosomal dominant way and nine were inherited in autosomal recessive way. The patients had vertebral segmentation anomalies accompanied with variable joint contractures, short stature and dysmorphic facial features. There was a significant phenotypic overlap between dominant and recessive MYH3-associated conditions regarding the degree of short stature as well as the number of vertebral fusions. All monoallelic variants caused significantly decreased SMAD3 phosphorylation, which is consistent with the previously proposed pathogenic mechanism of impaired canonical TGF-β signaling. Most of the biallelic variants were predicted to be protein-truncating, while one missense variant c.4244T>G,p.(Leu1415Arg), which was inherited in an autosomal recessive way, was found to alter the phosphorylation level of p38, suggesting an inhibition of the non-canonical pathway of TGF-β signaling. In conclusion, the identification of 12 novel pathogenic variants and overlapping phenotypes in 17 affected individuals from 10 unrelated families expands the mutation and phenotype spectrum of MYH3-associated skeletal disorders. We show that disturbances of canonical or non-canonical TGF-β signaling pathways are involved in pathogenesis of MYH3-associated skeletal fusion (MASF) syndrome.

Case Report: Inversion of LMX1B - A Novel Cause of Nail-Patella Syndrome in a Swedish Family and a Longtime Follow-Up

Nail-patella syndrome (NPS, OMIM #161200) is a rare autosomal dominant disorder with symptoms from many different parts of the body, including nails, knees, elbows, pelvis, kidneys and eyes. It is caused by truncating variants in the LMX1B gene, which encodes a transcription factor with important roles during embryonic development, including dorsoventral patterning of the limbs. To our knowledge, inversions disrupting the LMX1B gene have not been reported. Here, we report a family with an inversion disrupting the LMX1B gene in five affected family members with mild but variable clinical features of NPS. Our finding demonstrates that genomic rearrangements must be considered a possible cause of NPS.

Allergy and autoimmune disease: a registry-based study

BACKGROUND

Allergy and autoimmunity are two potential outcomes of a dysregulated immune system, but the relationship between them is unclear. It has been hypothesized that they could be inversely associated because of different T helper cell reactivity patterns. However, both positive and negative associations have been reported. Therefore, our aim was to perform a large epidemiological study with a defined allergic disease cohort.

METHODS

During the years 1990-2002, 68 770 subjects were tested for total serum IgE (Total-IgE) and 72 228 were tested with Phadiatop for diagnosing allergic disease at Karolinska University Hospital, Stockholm, Sweden. This cohort was then linked with the Swedish Inpatient Registry 1968-2004 for a follow-up with regard to recorded discharges for 28 autoimmune diseases. We then used Cox regression and logistic regression to estimate the risk of autoimmune diseases in general in the allergy-tested subjects.

RESULTS

Subjects with positive Phadiatop test were at a statistically decreased risk of subsequent autoimmune disease in comparison with subjects with negative test; hazard ratio (HR): 0.80 [95% (Confidence interval) CI: 0.68-0.94). Prior autoimmune disease was associated with a decreased risk of positive Phadiatop test [odds ratio: 0.83 (95% CI: 0.72-0.96)] in comparison with negative test. Subjects with highly elevated Total-IgE were at a statistically increased risk of a subsequent autoimmune disease in comparison with subjects with normal levels [HR: 1.36 (95% CI: 1.09-1.70)], but no association was found between prior autoimmune disease and different Total-IgE levels.

CONCLUSION

The study supports the hypothesis that allergy, defined as positive Phadiatop test, could be inversely related to autoimmune disease but this association is weak.