Turner's syndrome

Turner's syndrome is characterized by a female phenotype with short stature, webbed neck, ovarian dysgenesis, cubitus valgus, and congenital heart disease (CHD).[1] Skeletal abnormalities and malformations of the chest are known features of Turner's syndrome and include a trapezoidal chest (shieldchest deformity), enlarged shoulders, mild pectus excavatum, and wide-spaced nipples.[1,2] The genotype usually is 45,X (less frequently, 46,X +, partial deletions of one X chromosome). There are few data published about the sternum in Turner's syndrome, though there is one report on the sternum in Noonan's syndrome[3] which resembles the Turner's syndrome phenotype but has a normal chromosomal pattern. Patients with other chromosomal aberrations, such as trisomy 21 and trisomy 18, also are known to have sternal abnormalities such as premature fusion with shortening of the sternum and multiple ossification centers in the manubrium. A high association of premature fusion of the manubrio-sternal (M-S) junction and short sternum (Currarino-Silverman syndrome) and CHD has been reported in the literature.[4,5] Hypoplasia, bifidity, and even absence of the sternum have been reported in association with C H D. Since there is no report on systematic analysis of sternal anomalies in Turner's syndrome, we reviewed lateral chest roentgenograms of 15 children and adolescents with Turner's syndrome to study sternal patterns, including premature fusion of the ossification centers and the M-S junction, the sternal body-to-manubrium ratio, and sternal length.

METHODS AND MATERIALS

All children with previously diagnosed Turner's syndrome from our cardiology clinics were reviewed or evaluated by a pediatric cardiologist and geneticist. The diagnosis of Turner's syndrome was made on the basis of clinical findings and was confirmed by blood karyotype. Any child without confirmatory blood karyotype and an adequate lateral chest roentgenogram was excluded from the study. The lateral chest roentgenograms of all patients were reviewed for the overall sternal length, sternal body-to-manubrium ratio, and state of fusion of the mesosternum and the M-S junction by at least two authors in this study. These sternal values were compared with data collected from 162 lateral chest roentgenograms of normal children and adolescents. In the normal group, only films with well-defined tipper and lower ends of the sternum and without chest deformity were included. Any child with CHD or median sternotomy was excluded from the normal group. The lengths of sternal body, manubrium, and its ratio were recorded in all normal children. The recorded measurements were analyzed for normal mean length of the sternum (top of the manubrium to the lower end of the ossified sternebrae), adjusted for age and sex of the patients. Measurements of sternal lengths were summarized by the mean and standard deviation for the entire data set and for the age-sex subgroup. The tube-film distances in patients older than 1 year were done at 70 inches (magnification about 10 percent) while those less than 1 year were done at 40 inches on the tabletop (magnification factor about 20 percent). A color Doppler echocardiogram was performed in all but one patient. Additionally, cardiac catheterization and angiography were performed in six patients with coarctation of the aorta.

RESULTS

Table 1 summarizes the normal maximum and minimum lengths of the sternum in each age and sex group, the mean length, and standard deviation in normal children. The mean ratio of the body of the sternum to the manubrium in the normal group was found to be 1. 99 (S D = 0.33). Of 162 normal children, none had premature fusion of the M-S junction or a short sternum; 3 had a narrow M-S junction, 4 had premature fusion of the mesosternum, and the other 7 had only two sternal segments. The clinical data and radiologic findings of the sternum in patients with Turner's syndrome are summarized in Table 2. The patients' ages ranged from 2 weeks to 20 years at the time the chest roentgenograms were done. Only three patients had a normal configuration and length of sternum as shown by the lateral chest roentgenograms. Five patients had a short sternum (less than 2 SD below the mean of the age-adjusted lengths; Table 1 lists the normal values), 4 patients had sternal lengths in the lower limits of normal; 6 had a sternum of normal length. Three patients (cases 7, 8, and 14) had premature fusion of the M-S junction and 3 other patients had a very narrow, almost fused, M-S junction. Four patients, who were less than 16 years of age, had premature fusion of the mesosternum. Three other patients had only two sternal body segments. There were two manubrial ossification centers in three patients (cases 5, 9, and 10). The ratio of the sternal body to the manubrium was found to be abnormally low in five patients, at the lower limit of normal in three others, and normal in seven patients. Patient 9 had a short sternum with an unusually angular first sternal segment (Fig 1). Four patients had anterior bowing of the sternal body as evidenced on a lateral chest roentgenogram (Fig 2); three of them had clinical signs of pectus excavatum. Two of them also had fused mesosternum. Except case 9, none received growth hormone therapy at the time the chest roentgenograms were done and none of the patients had signs of stress fracture on the chest roentgenogram. Four patients had a coarctation of the aorta, two had isolated bicuspid aortic valve, and two had both. All 6 patients with coarctation of the aorta had angioplasty and case 5 had aortic valvotomy, additionally None had mitral valve prolapse or dilatation of the aortic root. Of 15 patients, 10 had monosomy (7 patients had CHD), 3 had isochromosome Xq (1 had CHD), and 2 had mosaicism (none had CHD) on the blood karyotype. In our series, none had a ring pattern of chromosomes.

[TABULAR DATA 2 OMITTED]

DISCUSSION

Various skeletal abnormalities are associated with Turner's syndrome.[1] These include short stature, cubitus valgus, midfacial hypoplasia with undergrowth of the maxilla, small mandible, high arched palate, short fourth metacarpal bones, increasing angulation of the carpal bones, Madelung's deformity, talipes cavus, irregular tibial metaphyses, somewhat android configuration of the pelvis, scoliosis, and lack of lumbar lordosis. These skeletal changes are not diagnostic but are helpful in the diagnosis of Turner's syndrome. Short stature is the most important skeletal finding that leads to the consideration of Turner's syndrome diagnosis. Noonan's syndrome, which is phenotypic Turner's syndrome with a normal karyotype, has many of these skeletal changes including short stature.

Dupuis et al[2] have reported that thoracic malformation in Turner's syndrome is common (occurring in 19 of 41 patients) and quite specific on a lateral chest roentgenogram. It includes enlargement of the M-S junction with the angle of Louis frequently less than 150[degrees], pectus excavatum, and enlargement of the thorax with wide-spaced nipples. In Noonan's syndrome, pectus excavatum and carinatum deformity are frequent and of severe degree.[1,3] Hoeffel et al[3] reported various abnormalities of the sternum on a lateral chest roentgenogram in 14 patients with Noonan's syndrome and CHD. All but one patient in their series had some form of sternal abnormality including premature fusion of the M-S junction or mesosternum, causing pectus carinatum deformity, short sternum, and decreased ratio of the sternal body to the manubrium. In our series of 15 patients with Turner's syndrome, 12 (80 percent) had sternal abnormalities shown on the lateral chest roentgenogram. Four patients had complete premature fusion of the mesosternum, which rarely is found before the age of 16 years in normal development. Additionally, three patients had only two sternal body segments. This could be due to failure of original segmentation or due to premature synostosis of the sternebrae. Three patients had premature fusion of the M-S junction, but three others had an extremely narrow, almost fused, M-S junction. The manubrium and mesosternum usually remain unfused throughout life, but synostosis of these bones is reported to occur in about 10 percent of normal adults. The decrease in the ratio of sternal body to the manubrium in five patients may be due to short sternal body length or an increase in the length of manubrium, or both. Five patients had an overall short sternum in our series. Three patients had two ossification centers of the manubrium, which commonly is reported in children with Down's syndrome. Four of the 15 patients in our series had an unusual bowing of the mesosternum; three of them had mild clinically evidenced pectus excavatum. It is possible that the bowing of the mesosternum may be playing some role in the shieldchest deformity as well as pectus excavatum in Turner's syndrome. In contrast to Noonan's syndrome, our report and that of Dupuis and coworkers[2] suggest that pectus excavatum is mild and uncommon in Turner's syndrome, although Jones[1] has reported mild but frequent pectus excavatum in children with Turner's syndrome. Although some of our patients had premature fusion of the M-S junction, mesosternum, or both, none had Currarino-Silverman syndrome (pectus carinatum type 2 deformity), as evidenced by clinical examination and by chest roentgenogram, or pectus carinatum type 1 deformity.[5] In our series, 6 patients were young (at or younger than 15 months in age), and thus some potential radiologic abnormalities of the sternum may not yet have been evident, such as premature fusion of the M-S junction or fusion of the mesosternum.

Although none of the radiologic abnormalities of the sternum are pathognomonic for Turner's syndrome, the combination of the described radiologic findings in a female with either a bicuspid aortic valve or coarctation of the aorta predominantly is seen in Turner's syndrome. Absence of short stature in patients with Turner's syndrome is very rare but occurs in up to 5 percent of patients with mosaic Turners syndrome.[2] Short stature and similar radiologic findings also are reported in Noonan's syndrome, but Noonan's syndrome predominantly is associated with pulmonary stenosis.[3] Premature fusion of the M-S junction and sternal ossification centers (Currarino-Silverman syndrome), which results in a short sternum and a high carinate deformity of the chest, commonly is associated with CHD (>50 percent incidence), usually ventricular septal defect, patent ductus arteriosus, or atrial septal defect.[4,5] Nevertheless, short stature has not been reported with Currarino-Silverman syndrome.

Bicuspid aortic valve is the most common CHD reported in patients with Turner's syndrome.[6] Coarctation of the aorta and aortic valvar stenosis are the next frequent CHDs in Turner's syndrome, respectively Our findings and those of others[6,7] suggest that patients with 45,X karyotypes have the highest risk of CHD (7 of 10 patients in the present series). In our series as well as that of Mazzanti et al[6] series, coarctation of the aorta was found only in the 45,X group. Of the three patients with isochrome Xq in our series, only one had CHD (bicuspid aortic valve) and, of two patients with mosaicism, none had CHD. Others[6,7] have reported variable prevalence of CHD in few patients with these karyotypes. Our findings and those of others[6,7] suggest a definite connection between coarctation of the aorta and the 45,X karyotype in Turner's syndrome, thus indicating that the factors determining this feature may be localized on the X chromosome. Furthermore, Mazzanti and coworkers[6] reported two patients with partial anomalous pulmonary venous connection with 45,X karyotype, which is a rare combination.

The main genetic defects in Turner's syndrome are reported on the short arm of the X chromosome, and the severity of the clinical presentation (short stature and CHD) correlates with the extent of the deletion. It is possible that much of the short stature results from a skeletal dysplasia consequent to the chromosomal abnormality Despite a positive response to human growth hormone therapy in the Turner's syndrome patient, there is no evidence of growth hormone deficiency. On the contrary, these thoracic deformities and heart disease may occur as isolated anomalies or part of a generalized polymalformative syndrome or connective tissue disorder (eg, Down's, Noonan's, and Marfan's syndromes). Our findings of sternal abnormalities in Turner's syndrome and those of Hoeffel et al[3] in Noonan's syndrome are somewhat similar, suggesting a common connective tissue disorder in both conditions. Unlike the series of Hoeffel et al,[3] Turner's syndrome patients with or without CHD had similar sternal abnormalities. This finding suggests that sternal abnormalities in Turner's syndrome are part of the overall skeletal dysplasia and are independent of associated CHD. A recombinant DNA technology using a series of DNA probes that detect differences (restriction fragment length polymorphisms) among X chromosomes may be useful in identifying the loci for skeletal anomalies and CHDs in Turner's syndrome.[10] This is the first report that systematically analyzes the radiologic abnormalities of the sternum in Turner's syndrome.

ACKNOWLEDGMENT: We thank Cathy Munsey for her expert secretarial help and for typing the manuscript.

REFERENCES

[1] Jones KL. Smith's recognizable patterns of human malformation. 4th ed. Philadelphia: WB Saunders, 1988; 7-9, 108-09 [2] Dupuis C, Deminatti M, Maillard E, Nuyts JP, Cousin J, Frison B, et al. Les cardiopathies du syndrome d'Ullrich-Turner. Arch Franc Ped 1971; 28:395-416 [3] Hoeffel JC, Pernot C, Junker P. Radiologic patterns of the sternum in Noonan's syndrome with congenital heart defect. Am J Dis Child 1981; 135:1044-46 [4] Currarino G, Silverman FN. Premature obliteration of the sternal sutures and pigeon-breast deformity. Radiology 1958; 70:532-40 [5] Chidambaram B, Mehta AV. Currarino-Silverman syndrome (pectus carinatum type 11) and mitral valve disease. Chest 1992; 102:780-82 [6] Mazzanti L, Prandstraller D, Tassinari D, Rubino I, Santucci S, Picchio FM, et al. Heart disease in Turner's syndrome. Helv Paediat Acta 1988; 43:25-31 [7] Vernant P, Corone P, de Grochy J, de Gennes JL, Emerit L. Le coeur dans le syndrome de Turner-Ullrich. Arch Mal Coeur 1966; 59:850-55 [8] Rapport R, Sauvion S. Possible mechanism for the growth retardation in Turner's syndrome. Acta Paediatr Scand 1989; 356(suppl):82-6 [9] Summitt RL, Tipton RE, Wilroy RS Jr, Martens PR, Phelan JP. X-autosome translocations: a review. Birth Defects 1978; 14(6C):219-47 [10] Connor JM, Loughlin SAR. Molecular genetics of Turner's syndrome. Acta Paediatr Scand 1989; 356(suppl):77-80 (*) From the Department of Pediatrics, James H. Quillen College of Medicine, East Tennessee State University, Johnson City, (Drs. Mehta, Chidambaram, and Garrett); and the Division of Pediatric Cardiology, University of Tennessee, Memphis (Dr. Suchedina). Supported by Children's Miracle Network Telethon, Holston Valley Hospital and Medical Center, Kingsport, Tenn. Manuscript received February 26, 1993; revision accepted May 27. Reprint requests: Dr. Mehta, Pediatrics, 310 State of Franklin Road, No. 301, Johnson City, Tenn 37605

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