Hyper IgE syndrome (HIES) is a rare primary immunodeficiency characterized by the triad of elevated IgE and eosinophilia, eczema, and recurrent skin and pulmonary infections. The autosomal dominant (AD) form of HIES results from mutations in STAT3 and is characterized by disordered inflammation, connective tissue, and skeletal abnormalities. Tissue-specific STAT3 deficiency in animals, cytokine and transcriptional array data, and careful clinical phenotyping have explained some of the pathophysiology of the immunologic and non-immunologic abnormalities of AD-HIES. In depth study of the role of STAT3 mutations in specific aspects of HIES may lead to better understanding and new approaches to treatment of conditions intrinsic to HIES that are common in the general population, such as staphylococcal infections, scoliosis, osteoporosis, bronchiectasis, and arterial aneurysms. As the genotypes of STAT3 deficiency are further characterized, genotype–phenotype correlations may emerge that will be informative regarding specific molecular interactions. Autosomal recessive forms of hyper IgE (AR-HIES) have also been reported. A single case of homozygous deficiency of the signal protein Tyk2 has been reported as well as a recessive syndrome with some features overlapping AD-HIES, but for which the genetic etiology is unknown. Better understanding of the pathophysiology and mechanisms of dominant and recessive hyper IgE syndromes will shed light on somatic and immune biology and may improve quality of life and survival for HIES patients.