Development, behaviour and sensory processing in Marshall-Smith syndrome and Malan syndrome: phenotype comparison in two related syndromes

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.

A THANATOPHORIC DYSPLASIA TYPE I CASE WITH A FGFR3 P.R248C MUTATION AND SURVIVAL BEYOND THE NEONATAL PERIOD

A Thanatophoric dysplasia, is a severe congenital anomaly which mostly causes stillbirth or death of the affected baby within hours due to respiratory insufficiency. The diagnosis of TD is typically suspected on ultrasound during the second trimester of pregnancy, when severe shortening of the long bones, frontal bossing, flattened vertebrae, and short ribs that result in a narrow thorax and bell-shaped abdomen, can be seen. Here, we present a case with prenatal ultrasonographic findings suggestive of TD, and highlight the patient's postnatal dysmorphic features and typical radiographic findings. The definitive diagnosis of TD type I (TDI) was made postnatally, when molecular genetic analysis revealed the previously described p.R248C mutation in FGFR3. This case is reported due to its relative long life span and the definitive molecular diagnosis that could be made during hospitalization.

Molecular characterisation of six patients with prolidase deficiency: identification of the first small duplication in the prolidase gene and of a mutation generating symptomatic and asymptomatic outcomes within the same family

Prolidase deficiency (PD) is a rare autosomal recessive connective tissue disorder caused by mutations in the prolidase gene. The PD patients show a wide range of clinical outcomes characterised mainly by intractable skin ulcers, mental retardation and recurrent respiratory infections. Here we describe five different PEPD mutations in six European patients. We identified two new PEPD mutant alleles: a 13 bp duplication in exon 8, which is the first reported duplication in the prolidase gene and a point mutation resulting in a change in amino acid E412, a highly conserved residue among different species. The E412K substitution is responsible for the first reported phenotypic variability within a family with severe and asymptomatic outcomes.