After fibroblast RNA studies revealed a mechanism consistent with LMNA haploinsufficiency, we used whole exome sequencing, bioinformatics analysis, and family studies to identify a novel, heterozygous missense variant in the Asteroid Homolog 1 gene (ASTE1 c.230T>C, p.Val77Ala) as a candidate susceptibility variant in fibromatosis for patients with LMNA haploinsufficiency and a potential genetic factor in the etiology of DD and LD. Here, LMNA is linked to fibromatosis.