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Prader-Labhart-Willi syndrome (PWS)--characterized by severe obesity, short stature, hypogonadism, and muscle hypotonia--appears to be an interesting model for body-composition abnormalities. Twenty-seven PWS patients (15 males and 12 females) aged 6-22 y underwent total-body analysis by dual-energy X-ray photon absorptiometry (DXA). For each PWS patient two age- and sex-matched control subjects were studied: one obese subject with a relative body weight (RBW [is greater than] 120%) and body mass index (BMI) similar to that of the patient and one normal-weight subject (RBW [is less than] 120%). Percentage body fat was significantly greater in PWS patients than in obese subjects (47.4 [+ or -] 7.2% compared with 41.9 [+ or -] 9.9%, P [is less than] 0.0001) and the same difference was evident for arms and legs but not for the trunk. Lean mass was significantly lower in PWS patients (26.4 [+ or -] 8.2 kg) than in normal-weight subjects (32.9 [+ or -] 10.2 kg) and even more so than in obese subjects (40.3 [+ or -] 13.2 kg) (P [is less than] 0.0001). The most affected regions were limbs; thus, the ratio of lean mass in the trunk to that in the limbs was significantly higher in PWS patients (1.19 [+ or -] 0.15) than in obese (1.07 [+ or -] 0.13) and normal-weight (1.07 [+ or -] 0.09) subjects (P [is less than] 0.002). The ratio of fat mass to lean mass was significantly higher in PWS patients than in obese subjects (0.90 [+ or -] 0.32 and 0.74 [+ or -] 0.27, P [is less than] 0.05). Bone mineral content (BMC) was significantly lower in PWS patients (1503 [+ or -] 46 g) than in normal-weight (1876 [+ or -] 677 g) and obese (2322 [+ or -] 773 g) subjects (P [is less than] 0.0001); this difference was most pronounced in the limb region. Bone mineral density (BMD) in PWS patients (0.993 [+ or -] 0.116 g/[cm.sup.2]) did not differ significantly from that of normal-weight subjects (1.033 [+ or -] 0.147 g/[cm.sup.2]) but was significantly lower than that of obese subjects (1.154 [+ or -] 0.139 g/[cm.sup.2]). The influence of age on body composition was assessed by comparing two age subgroups ([is less than] 12 y, n = 10; and [is greater than or equal to] 12 y, n = 17). The older PWS patients had higher adiposity, lower BMC, and dramatically lower BMD. Also, the lean mass deficit increased with age so that the ratio of fat mass to lean mass was close to 1. In conclusion, PWS patients showed a peculiar body composition, to some extent similar to that found in subjects deficient in growth hormone or even to sedentary and elderly people. These results suggest the importance of an accurate analysis of body composition in PWS patients.

Myelomeningocele (MMC), also known as spina bifida, is a condition characterized by protrusion of the spinal cord through a defect in the vertebral column. This disorder is congenital and results in a serious impairment of locomotor ability. The relationship between body composition and locomotor disability was determined in 59 subjects, age 0.3 to 29 years, with MMC. Aspects of body composition that were measured included body cell mass (BCM), intracellular and extracellular water (ICW and ECW), total body water (TBW), and total body potassium (TBK). In infants with MMC, body composition was normal. However, in children with MMC beyond three to four years of age, there was a significant reduction in BCM, an altered distribution of TBW (ECW increased while ICW decreased), and an increase in body fat compared with age-matched children that did not have MMC. Beyond age four, BCM and lean mass were partially replaced by adipose (fat) tissue. The reduction in BCM was greatest for those with the most severe cases of MMC. Children with MMC who retained some mobility had less severe reductions in BCM. TBK was reduced in children with MMC as a result of the growth retardation and muscle atrophy caused by MMC. It is concluded that nutrition and mobility programs should be started at an early age in children with MMC in an attempt to minimize the body composition changes that accompany MMC. (Consumer Summary produced by Reliance Medical Information, Inc.)