We report on a patient with de novo interstitial deletion of the long arm of chromosome 12: 46,XY,del(12)(q24.31q24.33). To our knowledge this is the first patient with this chromosomal abnormality reported. He was born with minor anomalies, ambiguous genitalia, tracheomalacia, and he was developmentally delayed at age 9 months. The phenotype associated with this deletion may be characteristic. However, because of the absence of reported cases of other patients with loss of this chromosomal region, we cannot delineate the specific phenotype further. Ambiguous genitalia or hypogonadism has been reported in other patients with chromosomal rearrangements involving 12q24.

The effects of an experimental reduced-protein (13 g/L), milk-based formula with a whey-casein ratio of 40:60 and added tryptophan (Trp) (490 mumol/L, or 100 mg/L; EF) were measured by growth and protein biochemistry in term infants from 0 to 12 wk postnatally. Newborn infants (n = 95) were randomly assigned to receive EF or conventional formula (15 g protein/L, whey-casein ratio of 60:40; CF) and compared with 58 breast-fed infants (BF). Growth velocity for weight, length, and head circumference was similar between groups. In 79 infants, blood was sampled preprandially at 4, 8, and 12 wk. For all times, plasma Trp was similar in BF and EF infants (58.4 +/- 10.4 vs 59.5 +/- 14.7 mumol/L, mean +/- SD) but lower in CF infants (53.4 +/- 8.4, P < 0.05). The plasma Trp-large neutral amino acid (AA) ratio was higher with EF than with CF, as was prealbumin (P < 0.05). Formula-fed infants had higher (P < 0.05) plasma urea, prealbumin, total essential AA, branched-chain AA, and threonine than did BF infants. A reduced-protein formula with added Trp resulted in Trp status similar to that in BF infants, without compromising growth or protein biochemistry compared with CF infants.