Omenn Syndrome Presenting with Striking Erythroderma and Extreme Lymphocytosis in a Newborn.

Omenn syndrome is an autosomal recessive form of "leaky" severe combined immune deficiency resulting in distinct phenotypic features. The patient described herein had an atypical presentation of Omenn syndrome, with conspicuous erythroderma and extreme lymphocytosis at birth, in contrast to the typical evolution of rash seen during the first few weeks of life. In addition, the skin findings were secondary to infiltration of CD8+ (cytotoxic) T-cells in contrast to the CD4+ (helper) T-cells typically seen, which broadens the Omenn syndrome phenotype.