We report on a case of apparent germline mosaicism in a family of two sisters carrying a novel 19p13.13 deletion. The 11-year-old proposita was referred for evaluation of macrocephaly, moderate intellectual disability (ID), and episodic ataxia. Array comparative genomic hybridization (CGH) detected a 399 kb microdeletion with breakpoints within genes NFIX and CACNA1A. A similar deletion was also seen in the elder sibling who presented with macrocephaly, ID, and strabismus. The deletions were confirmed to be de novo after the parental aCGH analysis suggesting that this is an example of germinal mosaicism. This study contributes additional information for the newly identified 19p13 deletion syndrome and clarifies the clinical roles of genes in the involved region. This case of apparent germline mosaicism represents the only known family in the cohort of 1,800 patients analyzed by our group. © 2013 Wiley Periodicals, Inc.