During infancy, this 50-year-old man with a previously undiagnosed multiple congenital anomalies/intellectual disability (MCA/MR) syndrome had grossly symptomatic hypercalcemia and was (briefly) thought to have Williams syndrome. Results of studies with the cytogenetic methods of the 1960s and 1970s were apparently normal. He matured late, but is high-functioning and healthy. Over 50 years he remained a diagnostic enigma. Thus, it came as a surprise when recent high-resolution banding methods showed an abnormality of the terminal portion of 13q, determined on array-comparative genomic hybridization to constitute an unbalanced chromosome rearrangement with a 0.35 Mb loss of 13q34-ter and 7.67 Mb gain of 14q32.2q32.33 translocated to 13q34. This apparently de novo genomic abnormality must be presumed as the cause of this previously undescribed MCA/MR syndrome which, however, may remain a private syndrome in this family. Williams syndrome was ruled out, and presently it is not possible to ascribe this patient's severely symptomatic infantile hypercalcemia to any gene on the deleted or duplicated chromosome segments. This “case” does underscore the importance of re-studying previously obscure but evidently genetic conditions, of long-term follow-up and documentation of natural history, and of providing, at last, a causal explanation to the family. © 2011 Wiley-Liss, Inc.