PT  - JOURNAL ARTICLE
AU  - Ziegler, Marvin
AU  - Russell, Bianca E.
AU  - Eberhardt, Kathrin
AU  - Geisel, Gregory
AU  - D'Amore, Angelica
AU  - Sahin, Mustafa
AU  - Kornblum, Harley I.
AU  - Ebrahimi-Fakhari, Darius
TI  - Blended Phenotype of Silver-Russell Syndrome and SPG50 Caused by Maternal Isodisomy of Chromosome 7
AID  - 10.1212/NXG.0000000000000544
DP  - 2021 Feb 01
TA  - Neurology Genetics
PG  - e544
VI  - 7
IP  - 1
4099  - http://ng.neurology.org/content/7/1/e544.short
4100  - http://ng.neurology.org/content/7/1/e544.full
SO  - Neurol Genet2021 Feb 01; 7
AB  - Objective Uniparental isodisomy can lead to blended phenotypes of imprinting disorders and autosomal recessive diseases. To determine whether a complex neurodevelopmental disorder was caused by uniparental isodisomy, a detailed clinical and molecular characterization was performed.Methods A combination of clinical, molecular, and imaging data and functional studies in patient-derived fibroblasts.Results We report a 4-year-old female with a blended, complex phenotype of Silver-Russell syndrome (SRS) and hereditary spastic paraplegia type 50 (SPG50) caused by total maternal isodisomy of chromosome 7 (UPiD(7)mat) and a loss-of-function variant in AP4M1 (NM_00472.3: c.59-1G>C, IVS1-1G>C). Functional studies in patient-derived fibroblasts confirmed the loss of adaptor protein complex 4 function. Distinctive facial features, intrauterine growth restriction, short stature, feeding difficulties, and severe gastroesophageal reflux were consistent with SRS. Features associated with SPG50 included early-onset epilepsy, episodes of stereotypical laughter, and thinning of the corpus callosum and ventriculomegaly on brain MRI. Symptoms shared by both syndromes such as developmental delay, short stature, and axial and appendicular hypotonia were also present. Notably, other common manifestations of SPG50 such as microcephaly or spasticity had not developed yet.Conclusions This case highlights that atypical clinical features in patients with well-described imprinting disorders should lead to investigations for recessive conditions caused by variants in genes that localize to the region of homozygosity.AP-4=adaptor protein complex 4; ATG9A=autophagy-related protein 9A; CDC=Centers for Disease Control and Prevention; SPG50=spastic paraplegia type 50; SRS=Silver-Russell syndrome; SSMD=strictly standardized mean difference