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Noonan Syndrome (NS) is a multisystem disorder, caused by dysregulation of the Ras/MAPK signaling pathway. Pathogenic gene variants in the Ras/MAPK pathway can therefore lead to various lymphatic diseases such as lymphedema, chylothorax and protein losing enteropathy.
DCMRL and T2 imaging were performed in seven patients with NS and lymphatic diseases. Informed consent for publication was acquired from all parents and, when appropriate, patients aged 12 years or older. This research has been approved by the Medical Ethics Committee at Radboud University Medical Center Nijmegen (file number 2020-6852).
Patient 1: 11-year-old female was diagnosed with NS and a de novo pathogenic variant in SOS2 (c.800T>A p.(Met267Lys)). Prenatal ultrasounds showed polyhydramnios. She had no signs of the lymphatic disorders until six years of age, when she presented with lower extremity lymphedema. The T2 imaging showed a partially developed thoracic duct, pulmonary (interstitial) and periportal edema and lymphangiectasia in the retroperitoneal space and mesentery. DCMRL demonstrated retrograde lymphatic flow in the lung interstitium, mesenteric and periportal lymphatic vessels, findings that are consistent with CCLA.
Patient 2: 17-year-old female who was diagnosed with NS, with a pathogenic variant in SOS2 (c.800T>A p.(Met267Lys)). Prenatal ultrasounds showed an increased nuchal translucency (>3 mm) without polyhydramnios. She had no signs of the lymphatic disorders until the age of nine years, when she developed lymphedema of the lower extremities and abdominal wall. In addition, she had neuropathic pain in both feet. The T2 images suggested a partial aplasia of the thoracic duct, an enlarged cisterna chyli, peritoneal lymphatic cysts, lymphangiectasia in the retroperitoneal space, and subcutaneous body wall as well as signs of pulmonary interstitial edema were also noted. DCMRL showed no contrast opacification of the thoracic duct, and retrograde flow in the peribronchial, mesenteric and periportal lymphatic vessels, as well as dermal backflow in the abdominal wall, findings that are consistent with CCLA.
Patient 3: 32-year-old female was diagnosed with NS, and a de novo pathogenic variant in SOS2 (c.800T>C p.(Met267Thr)). Prenatal ultrasounds showed polyhydramnios. She presented with lymphedema in the extremities during infancy, which improved within the first few years of her life. At 16 years she again developed severe lymphedema of the upper and lower extremities. DCMRL showed a dilated, and in intermittently duplicated, thoracic duct, without cisterna chyli. However there was no failure to empty into the thoracic duct or the subclavian vein. In addition, there was no abnormal retrograde lymphatic flow or extravasation of contrast. Therefore, these findings were not consistent with CCLA, according to the definition of Ricci, K.W. et al. (2021)
Patient 4: 20-year-old male was diagnosed with NS and a pathogenic variant in RIT1 (c.280G>A (p.(Ala77Thr)). At the age of 6 years, he developed chylous ascites, followed by chylothorax, lymphedema of the lower extremities and scrotal area, and scrotal chylous leakage. The T2 imaging showed left-sided pleural fluids and mesenteric edema. DCMRL images showed partial aplasia of the thoracic duct, retrograde contrast flow into the scrotum as well as dermal backflow and lymphangiectasia behind the cecum and throughout the retroperitoneum, findings that are consistent with CCLA Figure 1.
Figure 1. DCMRL results of a 20-year-old male with NS. 1. Abnormal tortuous thoracic duct and partial aplasia. 2. Left-sided pleural fluid.
Patient 5: 31-year-old female was diagnosed with NS and pathogenic variant in PTPN11 (c.181G>A p.(Asp61Asn)). Prenatal ultrasound information was not available. At the age of one year she developed chylothorax after cardiac surgery for repair pulmonary valve stenosis. At the age of ten years she developed lymphedema of the lower extremities as well as vulvar and labial lymphangiectasia, and genital lymphorrhea. At the age of 26 years, she underwent surgical resection of the vulvar lymphangiectasia, which has been reported by Winters et al. [24] T2 imaging shows a dilation of the thoracic duct and lymphangiectasia behind the cecum and throughout the retroperitoneum. DCMRL showed dermal backflow towards the labia, lower extremities, and the abdominal wall, findings that are consistent with CCLA.
Patient 6: 27-year-old male was diagnosed with NS and a pathogenic variant in SOS1 (c.1277A>C p.(Gln426Pro)). During adulthood, he was diagnosed with protein losing enteropathy. T2 images showed a normally developed thoracic duct. DCMRL demonstrated normal antegrade flow in the thoracic duct however retrograde flow into the mesentery; which can potentially explain the protein losing enteropathy, findings that are consistent with CCLA.
Patient 7: 34-year-old male was diagnosed with NS and pathogenic variant in PTPN11 (c.182A>G (p.Asp61Gly)). He was diagnosed with pericardial effusion at the age of 18 years, and chylothorax at the age of 32. T2 imaging visualized bilateral pleural and pericardial fluid as well as ascites, mesenterial and subcutaneous edema and pelvic cysts. DCMRL showed a tortuous, dilated and partially duplicated thoracic duct, without cisterna chyli, as well as retrograde flow into the periportal lymphatic vessels and dermal backflow in the abdominal wall, findings that are consistent with CCLA.
The clinical lymphatic diseases of CCLA seen in these patients include lymphedema, chylothorax, genital lymph leakage and protein losing enteropathy. In all patients the thoracic duct was abnormal. In six patients the retrograde flow in the peribronchial, periportal or mesenteric lymphatic vessels, or dermal backflow was demonstrated.
Nr. |
Age (y) (m/f) |
Clinical Manifestation of Lymphatic Disease |
Radiological Findings |
Reference |
||
---|---|---|---|---|---|---|
TD |
Flow abnormalities |
Other findings |
||||
1 |
14 (f) |
CT, PLE, MLA, RLA |
ND |
Retrograde mesenteric and pulmonary flow |
Leak of contrast into duodenal lumen, abnormal CLS |
Dori, Y [13] |
2 |
13 (m) |
LE, PLE, HT |
ND |
Pleural fluids ascites |
oedematous intestine |
Keberle, M [17] |
3 |
17 (f) |
PLE |
absent |
ND |
abdominal collateral lymphatics and bilateral iliac lymphangiectasia |
Matsumoto, T [16] |
4 |
61 (m) |
LE, SLE |
Occlusion at the neck |
Increased pelvic and retroperitoneal flow |
PLA, abdominal ascites |
Othman, S [15] |
5 |
0.9 (f) |
CT |
Dilated |
Bilateral perfusion |
- |
Biko [1] |
6 |
0.6 (m) |
CT |
Double duct, central TD not present |
Bilateral perfusion |
Body wall edema |
Biko [1] |
7 |
0.1 (m) |
CT |
ND |
Bilateral pleural effusions |
Body wall edema, ascites |
Biko [1] |
8 |
0.8 (m) |
CT, ascites |
absent |
Bilateral perfusion |
Body wall edema, ascites |
Biko [1] |
9 |
7 (f) |
CT |
absent |
Bilateral perfusion |
Pericardial effusion, ascites |
Biko [1] |
10 |
0.2 (m) |
CT |
absent |
Bilateral perfusion |
Body wall edema |
Biko [1] |
11 |
0.1 (f) |
CT |
rudimentary |
Bilateral perfusion |
ascites |
Biko [1] |
12 |
0.1 (f) |
CT |
Double duct |
Perfusion right lung |
- |
Biko [1] |
13 |
0.1 (m) |
CT, anasarca |
Dilated |
Bilateral perfusion |
Network of lymphatic collaterals in left neck, body wall edema, ascites |
Biko [1] |
14 |
5 (m) |
ascites |
absent |
Peritoneum perfusion |
Ascites |
Biko [1] |
CLS: central lymphatic system, CT: chylo-thorax, f: female, HT: hydrocele testis, LE: lymphedema, m: male, MLA: mesenteric lymphangiectasia, ND: no data, PLA: pulmonary lymphangiectasia, PLE: protein losing enteropathy, RLA: retroperitoneal lymphangiectasia, SLE: scrotal lymphedema.