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Seckel syndrome, an autosomal recessive disorder is the most common of the microcephalic osteodysplastic dwarfisms. Seckel syndrome is characterized by a proportionate dwarfism of prenatal onset, a severe microcephaly with a bird-headed like appearance and mental retardation. Hematological abnormalities with chromosome breakage have only been found in 15 to 25% of patients. The differential diagnosis with microcephalic osteodysplastic dwarfism type II can only be made with a complete radiographic survey in the first years of life. Besides to a wide phenotypic heterogeneity between affected patients, genetic heterogeneity has also been proven, with three loci identified to date by homozygosity mapping: SCKL1 (3q22.1-q24, ataxia-telangiectasia and Rad3-related protein (ATR) gene), SCKL2 (18p11.31-q11.2, unknown gene) and SCKL3 (14q23, unknown gene). SCKL3 seems to be the predominant locus for Seckel syndrome. Approaching the function of the ATR gene, the genes with a role in DNA repair are good candidates for SCKL2 and 3. Mental retardation is usually severe and families should be helped for social problems. In case of associated hematological abnormalities (anemia, pancytopenia, acute myeloid leukaemia), medical treatment should be provided.
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