Utility of Genetic Testing in Fetal Alcohol Spectrum Disorder

OBJECTIVE

To study the utility of genetic evaluation and testing in patients with suspected fetal alcohol spectrum disorder (FASD).

STUDY DESIGN

We performed a retrospective chart review of all patients (n = 36) referred for evaluation for suspected FASD to the genetics clinic at Boston Children's Hospital between January 2006 and January 2013. Records of all patients were reviewed to obtain the medical history, family history, examination findings, and investigations, including genetic testing.

RESULTS

Of the 36 patients, definite prenatal exposure was documented in 69%. Eight patients did not fulfill clinical criteria for FASD. Chromosomal microarray analysis (CMA) detected 19 copy number variants (CNVs) in 14 patients. Among patients who fulfilled criteria for FASD and underwent CMA, pathogenic CNVs were detected in 3 patients (2q37del, 22q11.22dup, and 4q31.21del syndromes), giving a yield of 14.3%. All 3 patients had overlapping features between FASD and the genetic syndrome.

CONCLUSION

Genetic testing, especially CMA, should be considered in patients referred for evaluation of FASD, as a significant proportion have a clinically significant CNV even when they fulfill diagnostic criteria for FASD spectrum.

Bilaterally cleft lip and bilateral thumb polydactyly with triphalangeal component in a patient with two de novo deletions of HSA 4q32 and 4q34 involving PDGFC, GRIA2, and FBXO8 genes

We report on a newborn boy with a bilateral cleft of the primary palate, duplicated triphalangeal thumbs, and a patent foramen ovale. During childhood he had moderate developmental delay. Brain MRI at 4 years was normal. The concurrence of non-syndromic clefts of the lip/palate (CL/P) and duplicated thumbs with triphalangeal component has, to our knowledge, not been reported so far. In our case, array-CGH analysis documented two de novo deletions (∼1.2 Mb and ∼400 Kb) of the long arm of chromosome 4, containing four genes: platelet-derived growth factor C (PDGFC), glycine receptor beta subunit (GLRB), glutamate receptor ionotropic AMPA2 (GRIA2), and F-box protein 8 gene (FBXO8). PDGFC codes for a mesenchymal cell growth factor already known to be associated with clefts of the lip. Pdgfc(-/-) mice have skeletal anomalies, and facial schisis resembling human cleft/lip palate. GRIA2 codes for a ligand-activated cation channel that mediates the fast component of postsynaptic excitatory currents in neurons, and may be linked to cognitive dysfunction. FBXO8, a gene of unknown function, is a member of the F-box gene family, among which FBXW4, within the minimal duplicated region associated with human split-hand/foot malformation type 3 (SHFM type 3). The presence of overlapping deletions in patients who do not share the same phenotype of our case suggests incomplete penetrance, and a possible effect of modifier genetic factors.