Age-related variation of respiratory chemosensitivity in monozygotic twins

To examine age-related variations in respiratory chemosensitivity to hypoxia and hypercapnia, the magnitudes of within-pair variances for ventilatory responses to hypoxia and hypercapnia were measured in 38 pairs of male monozygotic twins. Mean values for the slope factor of end-tidal PO2-ventilation hyperbola (A) were larger in Group I (13 pairs with a mean age of 16.3 +/- SD 0.9 yr) than those in Group II (12 pairs with a mean age of 29.8 +/- 6 yr), and Group III (13 pairs with a mean age of 46 +/- 7.2 yr). The slope factors for end-tidal PCO2-ventilation line (S) were similar among the 3 groups. Within-pair variances for A, A/body surface area (BSA), and Vo (asymptote for ventilation when end-tidal PO2 is infinite) were larger in Groups II and III than in Group I. Within-pair variances for S and S/BSA were also larger in Groups II and III than in Group I, whereas within-pair variances for B (intercept with end-tidal PCO2) were similar among the 3 groups. These results indicate that variations for respiratory chemosensitivity to hypoxia increase during the period from adolescence to adulthood and stay at a similar level thereafter. Variations of hypercapnic chemosensitivity also increase during this period, attenuating thereafter; however, the variation is 7 times larger than that of hypoxic chemosensitivity in the third and fourth decades.     

Multiple rhabdomyomas in monozygotic twins.

Rhabdomyoma is the most frequent primary cardiac tumor seen during infancy. We report multiple rhabdomyomas diagnosed in twins in the neo natal period. To the best of our knowledge, this is the first instance of this happening.     

Achalasia in monozygotic twins

Summary The familial occurrence of achalasia has been previously recorded and a genetic origin for the disease has been postulated. We present the first case of achalasia in monozygotic twins and suggest that concordance for the disease is consistent with a genetic factor in the etiology of achalasia.     

Discordance for ankylosing spondylitis in monozygotic twins.

Three monozygotic twin pairs, each over the age of 45 years, with ankylosing spondylitis are described. In two pairs there is discordance for this disease and in the third pair there is a marked difference in the severity of this disease. These findings provide evidence that environmental factors are necessary not only for the initial development of ankylosing spondylitis, but possibly also for determining its future severity.     

Focal myositis in monozygotic twins

Focal myositis is a rare disease with unknown etiology and a broad spectrum. Here, we present two cases in monozygotic twins who complained of recurrent pain of their calves and showed histological signs of inflammation and MRI image compatible with the diagnosis of focal myositis. The occurrence of twin cases not living in the same household suggests a genetic susceptibility to the disease.     

P-ANCA in monozygotic twins with inflammatory bowel disease.

Perinuclear antineutrophil cytoplasmic antibodies (P-ANCA) have been demonstrated in patients with ulcerative colitis and in a higher frequency than expected in their first degree relatives. A hypothesis was proposed that P-ANCA is genetically determined and may represent a subclinical marker of genetic susceptibility to ulcerative colitis. This study analysed P-ANCA in monozygotic twins with inflammatory bowel disease to evaluate this hypothesis further. P-ANCA was analysed with indirect immunofluorescence technique in 12 monozygotic twin pairs with ulcerative colitis and 14 twin pairs with Crohn's disease. Furthermore, the study included 21 non-twin patients with ulcerative colitis, 18 non-twin patients with Crohn's disease, and 52 healthy controls matched for sex and age. In ulcerative colitis P-ANCA occurred in nine of 14 (64.3%) monozygotic twins and in 13 of 21 (61.9%) non-twin cases, which was significantly different compared with healthy controls who were positive in three of 52 (5.8%) cases (p < 0.0001). P-ANCA was found in two of 10 (20%) healthy twin siblings to twins with ulcerative colitis, which was not significantly different from healthy controls (p = 0.18). The results in Crohn's disease did not differ from healthy controls. Previous findings of P-ANCA occurring in ulcerative colitis but not in Crohn's disease are supported. This study does not support the hypothesis that P-ANCA is a subclinical marker of genetic susceptibility to ulcerative colitis.     

Tetralogy of Fallot in monozygotic twins

A pair of monozygotic twins having tetralogy of Fallot is reported for the first time in the Indian literature. This case report will help in further enriching the existing data on genetic hypothesis of congenital heart defects.     

Occurrence of scleroderma in monozygotic twins

Familial occurrence of scleroderma is rare and concordance for the disease in twins has been reported exceptionally. We describe 2 female identical twin pairs concordant for scleroderma. The first twin pair was diagnosed with the systemic form of scleroderma, the second pair with the localized form.     

Gastroesophageal reflux disease in monozygotic and dizygotic twins.

BACKGROUND & AIMS: Gastroesophageal reflux disease (GERD) interferes with the quality of life and carries an increased risk for esophageal adenocarcinoma. We investigated genetic influence in the development of reflux. METHODS: We compared concordance for reflux in monozygotic (MZ) and dizygotic (DZ) twins. All twins age 55 and older in the nationwide Swedish Twin Registry were invited to participate. Data were collected by computer-assisted telephone interviews. Reflux disease was defined by symptomatic heartburn or acid regurgitation occurring at least weekly. RESULTS: A total of 2178 monozygotic, 3219 same-sex dizygotic, and 3014 unlike-sex dizygotic twin pairs provided information. Overall, 15.3% of the twins had reflux. In men, the intraclass correlation for reflux was 0.29 (95% confidence interval [CI], 0.15-0.43) for monozygotic and 0.13 (95% CI, 0.02-0.25) for dizygotic pairs. In women, the correlation was 0.33 (95% CI, 0.22-0.44) for monozygotic and 0.14 (95% CI, 0.04-0.24) for dizygotic pairs. For unlike-sex dizygotic pairs, the correlation was 0.06 (95% CI, -0.01 to 0.14). Concordance for reflux was not caused by inherited obesity or alcohol use; inherited smoking may be a minor factor. CONCLUSIONS: The increased concordance for reflux in monozygotic pairs, compared with dizygotic pairs, indicates genetic rather than shared environmental effects. Heritability accounted for 31% (23%-39%) of the liability to reflux disease in this population.     

Tracheobronchial clearance in asthma-discordant monozygotic twins

Tracheobronchial clearance and bronchial reactivity were studied in 6 asthma-discordant monozygotic twin pairs, and in 3 concordant pairs as controls. Clearance of 6-microns Teflon particles labeled with 99mTc was followed for 2 h. The results indicate that clearance in the larger airways is usually not severely impaired in mild to moderate asthma, and that it may be increased as well as decreased. Bronchial reactivity correlated with clearance in the nonasthmatics.     

Bicuspid aortic valves in monozygotic twins

Identical bicuspid valve anomalies were found in monozygotic twins. Screening echocardiography should be considered for first-degree relatives of patients with bicuspid aortic valve.     

Hepatitis C virus in monozygotic twins

A case of a pregnant patient with chronic hepatitis C who gave birth to monozygotic twins that were infected with HCV is reported. One of the newborns was positive for HCV-RNA in blood sample collected 12 hours after delivery. The other newborn was negative for HCV-RNA at birth, but was detected HCV viremia at three months of age. The results have led to the conclusion that one of the twins was probably contaminated in the intrauterine period, while the other acquired the infection in the perinatal period. Both were negative for HCV-RNA and for anti-HCV in the serum samples collected at nine months of age. The report describes the changes in the laboratory tests conducted in mother and twins until 29 months after delivery.