(Digeorge syndrome)
Radiology Cases in Pediatric Emergency Medicine Volume 2, Case 2
Loren G. Yamamoto, MD, MPH

This is a 2 month old male with a history of a VSD arriving in the ED for a possible seizure. He has had some cold symptoms since yesterday. This evening, his parents noted an episode of body stiffness, jerking of all extremities, and upward rolling of his eyes lasting one minute. An ambulance was called. His face was described as being blue toward the end of the episode. Paramedics noted him to be breathing spontaneously with no cyanosis. He was transported to the ED. An IV was attempted en route, but this was not successful. No fever was noted in the ambulance. There was no history of fever prior to this episode.

VS T36.6 (rectal), P132, R60, weight 4.36 kg. He was alert and active. Fontanelle soft and flat. Neck supple. Heart regular, harsh grade III/VI systolic murmur. Lungs clear. Good color, perfusion, and tone. Shortly after arrival in the ED, another seizure was witnessed. His upper extremities were flexed and jerking. His lower extremities were extended and jerking. No one could recall what his eyes were doing. An IV was attempted during the seizure but this was not successful. The seizure stopped on its own after five minutes. His oxygen saturation was 100% throughout the seizure with an oxygen mask in place. After the seizure, he was crying. He was not drowsy. He was moving around a lot during other IV attempts. He was noted to be very strong. An IV was started. He was given 0.1 mg/kg of lorazepam and 10 mg/kg of phenobarbital. He was more sedated at this point. His respiratory effort and perfusion remained good.

A CBC, blood culture, electrolytes, glucose, and calcium were drawn. A quick glucose check was 175 mg/dl.
He was given 50 mg/kg of cefotaxime IV. A portable chest radiograph was obtained and a CT of the head was ordered.

There is cardiomegaly with slightly prominent pulmonary vascularity suggesting a left to right shunt. Compare this CXR to his CXR taken at birth.

Birth history:

He was born to a 22 year old G3P2, O+, rubella immune, syphilis negative, hepatitis B negative mother at 40 weeks gestation via spontaneous vaginal delivery weighing 3.9 kg with apgar scores of 8 and 9. Membranes were ruptured at delivery. Amniotic fluid was clear. His newborn exam noted small ears. A heart murmur was not noted initially, but two hours after birth a grade II/VI systolic murmur was noted. A CXR taken at birth [Click on Birth] showed cardiomegaly without pulmonary edema. An echocardiogram performed the next day showed a large VSD with an overriding aorta and a relatively narrow main pulmonary artery (consistent with a mild Tetralogy of Fallot; however, minimal pulmonic stenosis and no right to left shunting). Despite the cardiomegaly noted on the CXR, the echocardiogram showed normal chamber sizes and contractility. He was discharged on day 2 of life. Several weeks later, he developed worsening congestive heart failure. He was treated with digoxin. Returning to the E.D. and his current condition, his head CT study was normal. Other lab results: CBC, WBC 5,300, 59% segs, 20% lymphs, 17% monos, 4% eos, Hgb 10, Hct 30, platelets 310,000. Na 133, K 4.4, Cl 91, Bicarb 26, glucose 144, Ca 6.0, digoxin level 2.0, creatinine 0.4. The calcium value is very low (normal 8.0-10.0 mg/dl). Mg and Phos levels were run when the low calcium was noted. Mg 1.9 (normal), Phos 8.9 (high, normal range 4.0-6.0). DiGeorge syndrome was suspected. Review of his CXR's revealed the absence of a thymic shadow consistent with thymic aplasia (a feature of DiGeorge syndrome). Review his CXR's again. They are very similar. Click on [Birth]. His newborn CXR shows a narrow superior mediastinum. In normal newborns, the superior mediastinum is enlarged due to the presence of a normal large thymus.

These two normal newborn CXR's show a normal thymus configuration. The upper mediastinum is wider than our DiGeorge patient's CXR. The normal thymus can be very large. It may sometimes protrude to the side exhibiting a "sail sign". The thymus may sometimes be elevated in a pneumomediastinum. The lateral view of the newborn CXR is most important in distinguishing these features. The normal newborn CXR will have the space anterior to the heart filled by the thymus.

In this lateral CXR, our patient with DiGeorge syndrome has no thymus. Thus, the space anterior and superior to the heart is empty. The radiologist who initially read his newborn CXR commented on the absence of a thymic shadow. The thymus can also be hypoplastic in the presence of physiologic stress such as sepsis and shock.

Further studies and clinical features confirmed the diagnosis of DiGeorge Syndrome. His parathyroid hormone level in the presence of hypocalcemia was low. DiGeorge syndrome is predominantly a syndrome of hypoparathyroidism and T-lymphocyte deficiency due to thymic aplasia or hypoplasia. The thymus and the parathyroid glands both arise from the same pharyngeal pouches (3rd and 4th) during embryogenesis. Failure of these pouches to develop results in deficiencies of the thymus and parathyroids. DiGeorge syndrome is classified as an immunodeficiency syndrome. Patients with DiGeorge syndrome are susceptible to opportunistic infections. However, patients with DiGeorge syndrome typically present initially with tetany and hypocalcemia (resembling seizures) due to hypoparathyroidism long before any immunodeficiency is appreciated. Other clinical features of DiGeorge syndrome include congenital heart and aortic defects, hypoplastic mandible, defective ears, and other subtle facial features. The expression of all the clinical features of DiGeorge syndrome is variable. Although a serum calcium measurement is often included in the laboratory evaluation of a child with a first time seizure, it is rarely abnormal. Febrile seizures are most common and are not associated with any electrolyte or calcium abnormalities.

DiGeorge syndrome is a rare occurrence when hypocalcemia is the cause of the "seizure" (tetany). Children under five months of age are unlikely to have benign febrile convulsions. Thus, a calcium measurement should be performed in all young infants (under 6 months) with an apparent seizure. The yield of a serum calcium measurement in older children is much lower. A seizure is difficult to distinguish from tetany in an infant. In this instance it appeared to be a true seizure as it was witnessed by an emergency pediatrician and many pediatric ED nurses.