Tuesday, October 12, 2021

Marshall-Smith syndrome

Inspired by a patient

Mulder PA, van Balkom IDC, Landlust AM, Priolo M, Menke LA, Acero IH, Alkuraya FS, Arias P, Bernardini L, Bijlsma EK, Cole T, Coubes C, Dapia I, Davies S, Di Donato N, Elcioglu NH, Fahrner JA, Foster A, González NG, Huber I, Iascone M, Kaiser AS, Kamath A, Kooblall K, Lapunzina P, Liebelt J, Lynch SA, Maas SM, Mammì C, Mathijssen IB, McKee S, Mirzaa GM, Montgomery T, Neubauer D, Neumann TE, Pintomalli L, Pisanti MA, Plomp AS, Price S, Salter C, Santos-Simarro F, Sarda P, Schanze D, Segovia M, Shaw-Smith C, Smithson S, Suri M, Tatton-Brown K, Tenorio J, Thakker RV, Valdez RM, Van Haeringen A, Van Hagen JM, Zenker M, Zollino M, Dunn WW, Piening S, Hennekam RC. Development, behaviour and sensory processing in Marshall-Smith syndrome and Malan syndrome: phenotype comparison in two related syndromes. J Intellect Disabil Res. 2020 Dec;64(12):956-969. doi: 10.1111/jir.12787. Epub 2020 Oct 9. PMID: 33034087.


Background: Ultrarare Marshall-Smith and Malan syndromes, caused by changes of the gene nuclear factor I X (NFIX), are characterised by intellectual disability (ID) and behavioural problems, although questions remain. Here, development and behaviour are studied and compared in a cross-sectional study, and results are presented with genetic findings. 

Methods: Behavioural phenotypes are compared of eight individuals with Marshall-Smith syndrome (three male individuals) and seven with Malan syndrome (four male individuals). Long-term follow-up assessment of cognition and adaptive behaviour was possible in three individuals with Marshall-Smith syndrome. 

Results: Marshall-Smith syndrome individuals have more severe ID, less adaptive behaviour, more impaired speech and less reciprocal interaction compared with individuals with Malan syndrome. Sensory processing difficulties occur in both syndromes. Follow-up measurement of cognition and adaptive behaviour in Marshall-Smith syndrome shows different individual learning curves over time. 

Conclusions: Results show significant between and within syndrome variability. Different NFIX variants underlie distinct clinical phenotypes leading to separate entities. Cognitive, adaptive and sensory impairments are common in both syndromes and increase the risk of challenging behaviour. This study highlights the value of considering behaviour within developmental and environmental context. To improve quality of life, adaptations to environment and treatment are suggested to create a better person-environment fit. 

Schanze D, Neubauer D, Cormier-Daire V, Delrue MA, Dieux-Coeslier A, Hasegawa T, Holmberg EE, Koenig R, Krueger G, Schanze I, Seemanova E, Shaw AC, Vogt J, Volleth M, Reis A, Meinecke P, Hennekam RC, Zenker M. Deletions in the 3' part of the NFIX gene including a recurrent Alu-mediated deletion of exon 6 and 7 account for previously unexplained cases of Marshall-Smith syndrome. Hum Mutat. 2014 Sep;35(9):1092-100. doi: 10.1002/humu.22603. Epub 2014 Jul 8. PMID: 24924640.


Marshall-Smith syndrome (MSS) is a very rare malformation syndrome characterized by typical craniofacial anomalies, abnormal osseous maturation, developmental delay, failure to thrive, and respiratory difficulties. Mutations in the nuclear factor 1/X gene (NFIX) were recently identified as the cause of MSS. In our study cohort of 17 patients with a clinical diagnosis of MSS, conventional sequencing of NFIX revealed frameshift and splice-site mutations in 10 individuals. Using multiplex ligation-dependent probe amplification analysis, we identified a recurrent deletion of NFIX exon 6 and 7 in five individuals. We demonstrate this recurrent deletion is the product of a recombination between AluY elements located in intron 5 and 7. Two other patients had smaller deletions affecting exon 6. These findings show that MSS is a genetically homogeneous Mendelian disorder. RT-PCR experiments with newly identified NFIX mutations including the recurrent exon 6 and 7 deletion confirmed previous findings indicating that MSS-associated mutant mRNAs are not cleared by nonsense-mediated mRNA decay. Predicted MSS-associated mutant NFIX proteins consistently have a preserved DNA binding and dimerization domain, whereas they grossly vary in their C-terminal portion. This is in line with the hypothesis that MSS-associated mutations encode dysfunctional proteins that act in a dominant negative manner.

Aggarwal A, Nguyen J, Rivera-Davila M, Rodriguez-Buritica D. Marshall-Smith syndrome: Novel pathogenic variant and previously unreported associations with precocious puberty and aortic root dilatation. Eur J Med Genet. 2017 Jul;60(7):391-394. doi: 10.1016/j.ejmg.2017.04.012. Epub 2017 Apr 24. PMID: 28442439.


Marshall-Smith Syndrome (MRSHSS) is a very rare genetic disorder characterized by failure to thrive and characteristic dysmorphic features associated with accelerated osseous maturation. We present a nine-year-old girl who was diagnosed with MRSHSS based on characteristic clinical features supported by the identification of a novel de novo pathogenic variant in the NFIX gene. The patient also presented with precocious puberty diagnosed at five years of age and had an abnormal GnRH stimulation test indicative of central precocious puberty. Central precocious puberty has not been described in association with MRSHSS previously in the medical literature and broadens our knowledge of the natural history of MRSHSS. The causes of advanced bone age in this syndrome are also reviewed. Additionally, the patient showed progressive dilatation of the aortic root. Although connective tissue abnormalities have been described in association with MRSHSS, aortic root dilatation has not. Understanding the mechanism of comorbidities such as advanced bone age and aortic root dilatation in MRSHSS patients enables future development of anticipatory guidance, preventative care measures, and treatment guidelines.


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