Seckel syndrome is a rare, autosomal recessive disorder characterized by intrauterine and postnatal growth retardation resulting in dwarfism, characteristic dysmorphic features, and intellectual disability. The dysmorphic facial features characteristic of SCKL are exemplified by severe microcephaly, beak-like nasal protrusion, receding forehead and lower jaw, narrow face, micrognathia, abnormally large eyes, and malformed ears, all giving a bird-headed profile. Occasionally, clinodactyly, hip dysplasia, radial dislocation, cryptorchidism, hirsutism, clitoridomegaly, dental abnormalities, corpus callosum agenesis, and others may also be observed. More than a hundred cases of SCKL have been reported worldwide. Although the exact incidence is not known, it is assumed that 1 in every 10,000 children is born with the condition.
The first locus for SCKL to be identified, SCKL1, was localized to chromosome 3q22.1-q24. The gene was later identified to be the ATR (Ataxia-Telangiectasia and RAD3-Related) gene. The ATR protein product plays an important role in the cellular response to DNA damage and has been found to be important for both development as well as somatic cell growth. Patients affected with SCKL have been shown to have fragile chromosomes, with several break points; an effect which can be attributed to the defect in DNA repair.