Cleidocranial dysplasia (CCD) is an autosomal-dominant condition characterized by hypoplasia/aplasia of clavicles, patent fontanelles, supernumerary teeth, short stature, and other changes in skeletal patterning and growth. In some families, the phenotype segregates with deletions resulting in heterozygous loss of CBFA1, a member of the runt family of transcription factors. In other families, insertion, deletion, and missense mutations lead to translational stop codons in the DNA binding domain or in the C-terminal transactivating region. In-frame expansion of a polyalanine stretch segregates in an affected family with brachydactyly and minor clinical findings of CCD. We conclude that CBFA1 mutations cause CCD and that heterozygous loss of function is sufficient to produce the disorder.

Thirty years old, white man, presented with congenital reddish slightly thicken facial lesion with scattered nodules on the left side, to dermatology clinic, seeking a cosmetic alleviate. He has no other complains (i.e., no bleeding, no headache, no eye pain or visual impairment). Also, the patient has noticed that the lesion slightly decreased with aging. Family history (FH) was irrelevant.

Objectives To test the hypothesis that somatic PIK3CA mutations would be found in patients with more common disorders including isolated lymphatic malformation (LM) and Klippel-Trenaunay syndrome (KTS). Study design We used next generation sequencing, droplet digital PCR (ddPCR), and single molecule molecular inversion probes (smMIPs) to search for somatic PIK3CA mutations in affected tissue from patients seen at Boston Children’s Hospital who had an isolated LM (n=17), KTS (n=21), fibro-adipose vascular anomaly (FAVA; n=8), or congenital lipomatous overgrowth with vascular, epidermal, and skeletal anomalies syndrome (CLOVES; n = 33), the disorder for which we first identified somatic PIK3CA mutations. We also screened 5 of the more common PIK3CA mutations in a second cohort of patients with LM (n=31) from Seattle Children’s Hospital. Results Most individuals from Boston Children’s Hospital who had isolated LM (16/17) or LM as part of a syndrome, such as KTS (19/21), FAVA (4/8), and CLOVES (30/32) were somatic mosaic for PIK3CA mutations, with 5 specific PIK3CA mutations accounting for ~ 80% of cases. Seventy-four percent of patients with LM from Seattle Children’s Hospital also were somatic mosaic for 1 of 5 specific PIK3CA mutations. Many affected tissue specimens from both cohorts contained fewer than 10% mutant cells. Conclusions Somatic PIK3CA mutations are the most common cause of isolated lymphatic malformations and disorders in which lymphatic malformation is a component feature. Five PIK3CA mutations account for most cases. The search for causal mutations requires sampling of affected tissues and techniques that are capable of detecting low-level somatic mosaicism, because the abundance of mutant cells in a malformed tissue can be low.