Autosomal dominant transmission of nonsyndromic diastasis recti and weakness of the linea alba

We report on vertical familial segregation of nonsyndromic anterior abdominal wall deficiency, characterized by diastasis recti and weakness of the linea alba. The proband is a 33-year-old female who underwent genetic counseling for intrauterine growth retardation of her son. On pedigree analysis three family members in three generations displayed diastasis recti and weakness of the linea alba (Fig. 1). All affected patients showed anterior abdominal deficiency (Fig. 2A,B) without associated dysmorphic features or internalmalformations. Theproband had normal growth parameters. Birth weight at term was 3,200 g (25th centile), length 50 cm (50th centile), and head circumference 35 cm (50th–75th centile). At present, her weight is 58 kg (50th–75th centile), height 161 cm (50th centile), and head circumference 55.5 cm (50th–75th centile). Her son was born at the 39th week of gestation. Birth weight was 2,500 g (below the 3rd centile), length 47 cm (below the 3rd centile), and head circumference 35 cm (50th centile). Growth parameters have been improved with time. At 8 months of age, weight was 7.700 kg (10th–25th centile), length 67 cm (10th centile), and head circumference 45 cm (50th centile). Echocardiography and abdominal ultrasonography were normal in all affected subjects, urethral obstruction sequence was excluded by urethral cistography, and mental development was normal. Chromosome analysis in the proband and her child was normal at 500-band resolution. The process of truncal ventral wall closure can be viewed as a circumferential convergence of the original cephalic, caudal, and lateral wall folds toward the umbilicus [Seno, 1961; Christ et al., 1983]. During maturation of the ventral wall, the ventral migration of the mesenchyme from the somites leads to relative overgrowth of the lateral folds and restrictionof the cephalic and caudal folds to two thin median triangular flaps overlying the sternum, linea alba, medial rectus sheaths, and pubic symphysis [Wyburn, 1937, 1938, 1939]. Timing and degree of involvement of the somatic and visceral layers play an important role in the resulting spectrum of malformations. These range from more severe anomalies involving many tissue components, such as Cantrell pentalogy [Cantrell et al., 1958; Carmi and Boughman, 1992] or cloacal and bladder extrophy [Martinez-Frias et al., 2001] to less severe defects, including epigastric/infraumbilical omphalocele and epispadias. Maturational defects of the lateral abdominal wall folds occurring after normal body wall closure may result in primary deficiency of muscle formation. Heterogeneous mechanisms and etiologies are known to be involved in this process, including primary deficiency of muscle formation [Reid et al., 1986] and secondary atrophy due to abdominal dilation from obstructive uropathy in the setting of ‘‘prune belly syndrome’’ [Hoagland and Hutchins, 1987]. ‘‘Prune belly syndrome’’ is a malformation sequence due to early urethral obstruction leading to bladder dilatation, distention of the fetal abdomen, and secondary hypoplasia of the abdominal wall muscles. In the present report, hypoplasia of the abdominal wall muscles with weakness of the linea alba and diastasis recti occurred as a maturation deficiency without an associated sequence or syndrome. Chan and Bird [2004] reported a similar family, presenting vertical transmission in three generations of the abdominal phenotype of ‘‘prune belly syndrome’’,