Expanding the phenotype of Seckel syndrome associated with biallelic loss-of-function variants in CEP63.

Seckel syndrome is an ultrarare autosomal recessive genetically heterogenous condition characterized by intrauterine and postnatal growth restriction, proportionate severe short stature, severe microcephaly, intellectual disability, and distinctive facial features including a prominent nose. Up to now, 40 patients with molecularly confirmed Seckel syndrome have been reported with biallelic variants in nine genes: ATR, CENPJ, CEP63, CEP152, DNA2, NIN, NSMCE2, RBBP8, and TRAIP. Homozygosity for nonsense variant (c.129G>A, p.43*) in CEP63 was described in three cousins with microcephaly, short stature, mild to moderate intellectual disability and diagnoses of Seckel syndrome. Here, we report a second family with three siblings who are compound heterozygous for loss-of-function variants in CEP63, c.1125T>G, p.(Tyr375*) and c.595del, p.(Glu199Asnfs*11). All siblings present with microcephaly, prominent nose, and intellectual disability but only one has severe short stature. Two siblings have aggressive behavior, a feature previously not reported in Seckel syndrome. This report adds two novel truncating variants in CEP63 and extends the clinical knowledge on CEP63-related conditions.