Ectrodactyly and Lethal Pulmonary Acinar Dysplasia Associated with Homozygous FGFR2 Mutations Identified by Exome Sequencing

ABSTRACT Ectrodactyly/split hand‐foot malformation is genetically heterogeneous with more than 100 syndromic associations. Acinar dysplasia is a rare congenital lung lesion of unknown etiology, which is frequently lethal postnatally. To date, there have been no reports of combinations of these two phenotypes. Here, we present an infant from a consanguineous union with both ectrodactyly and autopsy confirmed acinar dysplasia. SNP array and whole‐exome sequencing analyses of the affected infant identified a novel homozygous Fibroblast Growth Factor Receptor 2 (FGFR2) missense mutation (p.R255Q) in the IgIII domain (D3). Expression studies of Fgfr2 in development show localization to the affected limbs and organs. Molecular modeling and genetic and functional assays support that this mutation is at least a partial loss‐of‐function mutation, and contributes to ectrodactyly and acinar dysplasia only in homozygosity, unlike previously reported heterozygous activating FGFR2 mutations that cause Crouzon, Apert, and Pfeiffer syndromes. This is the first report of mutations in a human disease with ectrodactyly with pulmonary acinar dysplasia and, as such, homozygous loss‐of‐function FGFR2 mutations represent a unique syndrome. The upper frames of the picture demonstrate hand abnormalities and corresponding x‐ray in a newborn infant consistent with complex ectrodactyly. The lower frame shows the heart and severely hypoplastic lungs with histological picture consistent with acinar dysplasia. Homozygous FGFR2 mutations were identified in this infant.