Limbic Encephalitis as Presentation of a Sap Deficiency

X-linked lymphoproliferative disease (XLP) is a rare immune cell disorder caused by mutations in the Src homology 2 domain-containing gene 1A (SH2D1A). This gene, located on the X-chromosome, encodes a small cytoplasmic adaptor known as signaling lymphocytic activation molecule (SLAM) associated protein (SAP). SAP is expressed in natural killer cells (NK) and T-cells. It interacts with SLAM and plays a critical role in regulating signaling. Clinical manifestations of patients with XLP vary. Most patients die following exposure to Epstein Barr virus (EBV). 3] imbic encephalitis is characterized by profound memory impairment, dementia, seizures, usually complex partial, and psychiatric disturbances. On MRI, signal changes are detected on the medial sides of the temporal lobes or in the hippocampi. e report a patient with limbic encephalitis caused by SAP deficiency.