Hydrops fetalis (HF) consists of an abnormal accumulation of fluid in two or more fetal compartments, including
ascites,
pleural effusion,
pericardial effusion, and skin
edema. Almost all observed cases of HF are of the nonimmune type, the causes of which remain undetermined in 15% of patients. We report a newborn infant with
nonimmune hydrops fetalis (NIHF) and
congenital hypothyroidism. The infant's mother was healthy and there were no malformations of the placenta or umbilical cord. The infant did not show any structural abnormalities of his central nervous, cardiovascular, gastrointestinal, or urinary tract systems, and there was no evidence of
anemia,
infectious disease, or inborn error of metabolism. An immune-based process was unlikely, because the
blood group of the mother and infant was A-positive and results of an indirect Coombs test in the mother and a direct Coombs test in the infant were negative. The patient's condition gradually improved with
mechanical ventilation, repeated thoracocentesis, and
total parenteral nutrition. By day 5 of age the skin
edema,
pericardial effusion, and
ascites disappeared, but accumulation of significant amounts of chylous pleural fluid persisted. Because of
lethargy, FT4 and
thyroid-stimulating hormone levels were obtained and showed
hypothyroidism.
Thyroid hormone supplementation was then started, and within 4 days the infant became more vigorous and was weaned from
mechanical ventilation. After 7 days, the
chylothorax resolved completely as the serum
thyroxine level normalized. No reaccumulation of
pleural effusion was noticed. The infant started to
gain weight and was discharged from the hospital at 35 days of age. A possible pathophysiologic association between
congenital hypothyroidism and NIHF is discussed. NIHF may be caused by lymphatic congestion attributable to an impairment of lymphatic flow and a delayed return of lymph to the vascular compartment. There could be a possibility that because of
thyroid hormone deficiency in this patient, there was reduced
adrenergic stimulation of the lymphatic system. This could result in a sluggish flow of the lymph with engorgement of the lymphatic system, leakage of lymph into the pleura and the interstitial spaces, and the production of
chylothorax with NIHF. Animal studies demonstrate a direct relationship between lymph flow rate or lung liquid clearance and
adrenergic receptor activity in the lymphatic system. These observations support our hypothesis that deficient
adrenergic activity in
congenital hypothyroidism might lead to
chylothorax with NIHF in the fetus. We speculate that
thyroid hormone may play a role in the regulation of
adrenergic receptors in the lymphatic system and lungs, thus modulating both the lymphatic flow rate and lung liquid clearance, and facilitating the resolution of
chylothorax. Examination of thyroid functions should be included in the investigation of fetuses and neonates with NIHF of an obscure origin.