A 2-day-old term boy is transferred to a tertiary NICU for further diagnostic evaluation and management of respiratory failure. His prenatal course was normal. Delivery was complicated by prolonged rupture of membranes with arrest of labor, necessitating cesarean delivery. During resuscitation, respiratory distress with stridor, retractions, and poor color were noted, followed by bradycardia. A 6-French nasal suction catheter could not be advanced through either nare; however, an orogastric tube was passed into the stomach without difficulty. Positive pressure ventilation was performed and demonstrated success only after the mouth was opened. Due to continued hypoxemia and stridor, a laryngeal mask airway was placed. Apgar scores were 3 and 7 at 1 and 5 minutes of life, respectively. The infant was admitted to the special care nursery of a community hospital for stabilization before transfer to the NICU.On NICU admission, oral endotracheal intubation is successfully performed. Vital signs on admission are as follows: temperature, 99.5°F (37.5°C); heart rate, 147 beats/min; respiratory rate, 51 breaths/min; blood pressure, 76/54 mm Hg; and oxygen saturation, 100% on minimal conventional mechanical ventilator settings (synchronized intermittent mandatory ventilation/pressure support mode with tidal volume of 5 mL/kg; maximum inspiratory pressure, 25 cm H2O; positive end-expiratory pressure, 5 cm H2O; respiratory rate, 30 breaths/min; and fraction of inspired oxygen, 21%). Physical examination on admission is notable for ear asymmetry with bilateral dysmorphic microtia (Fig 1), intermittent stridor before intubation with clear lung sounds bilaterally after intubation, and borderline microphallus (stretched penile length of 2.2 cm). Eye examination reveals equal pupils responsive to light without abnormalities of the irises; fundoscopy is not performed on admission. Cardiac examination findings are within normal limits, without murmur, and with normal femoral pulses. Abdominal examination discloses a soft, nontender, nondistended abdomen without organomegaly. Neurologic examination is limited in the setting of intubation but reveals an alert infant with normal tone for gestational age, equal movements of all extremities, and intact palmar grasp bilaterally. Skin examination findings are normal, without rashes or lesions.Laboratory values (reference ranges) are notable for significant hypocalcemia, with an ionized calcium level of 3 mg/dL (0.75 mmol/L) (3.9–6.0 mg/dL [0.97–1.50 mmol/L]) and a serum calcium level of 5.5 mg/dL (1.3 mmol/L) (9–11 mg/dL [2.25–2.75 mmol/L]); hyperphosphatemia, with a phosphorus level of 8.5 mg/dL (2.75 mmol/L) (4.0–6.5 mg/dL [1.29–2.10 mmol/L]); a normal white blood cell count of 17,500/µL (17.5 × 109/L) (9,400–34,000/µL [9.4–34.0 × 109/L]); and lymphopenia, with an absolute lymphocyte count of 1,575/µL (1.575 × 109/L) (5,000/µL [5.0 × 109/L]; 95% confidence interval, 2,000–17,000/µL [2–17 × 109/L]). Further evaluation reveals a low intact parathyroid hormone level of 8.9 pg/mL (8.9 ng/L) (reference range, 15–65 pg/mL [15–65 ng/L]) with a normal serum 25-hydroxyvitamin D level of 26.6 ng/mL (66.39 nmol/L) (reference range, >20 ng/mL [>49.92 nmol/L]). Newborn metabolic screening is expedited and reveals undetectable T-cell receptor excision circles (TRECs).Chest radiography shows a small, hypoplastic thymus and 11 paired ribs and is otherwise normal, with a normal cardiac silhouette. Initial echocardiography shows suprasystemic right ventricular pressures with mild right ventricular hypertrophy and mild pulmonary artery branch stenosis but no structural lesions. The aortic arch is leftward with a normal branching pattern.CHARGE (coloboma, heart defects, atresia choanae, growth retardation, genital abnormalities, and ear abnormalities) syndrome (CS) was high on the differential diagnosis because of clinical concern for choanal atresia with bilateral dysmorphic microtia (Fig 1). However, significant and refractory hypocalcemia, lymphopenia, hypoplastic thymus, and undetectable TRECs led to consideration of 22q11.2 deletion syndrome (22q11.2DS, also known as DiGeorge syndrome, Shprintzen syndrome, conotruncal anomaly face syndrome, or velocardiofacial syndrome), with which there is significant phenotypic overlap with CS. (1)(2) The normal echocardiogram lowered suspicion for 22q11.2DS, as congenital heart disease is present in up to 85% of those with the syndrome. (3) In addition, Kabuki syndrome, (4) diabetic embryopathy, (5) and embryopathy due to maternal retinoic acid exposure (6) were considered due to their phenotypic similarities to CS.Nasal obstruction prompted consideration of congenital nasal pyriform aperture stenosis, which is critical to identify because of its association with holoprosencephaly. (7) The differential diagnosis for nasal obstruction also included choanal atresia, congenital nasal tumors, septal deviation, and congenital dacryocystoceles. The external ear deformities warranted consideration of branchio-oto-renal syndrome, renal coloboma syndrome, and mandibulofacial dysostosis with microcephaly, although notably, there is no known association between any of these conditions and hypocalcemia or lymphopenia. (8)(9)(10)Bilateral inner and middle ear dysplasia and bilateral membranous choanal atresia with associated posterior nasal aperture narrowing were identified on computed tomography of the head and face. There was no nasal pyriform aperture stenosis identified. Fundoscopy revealed a left chorioretinal coloboma and possible right optic nerve hypoplasia. Right-sided facial paralysis, consisting of absent right-sided facial activity during crying and attempted eye closure, was noted and consistent with right peripheral cranial nerve VII palsy. Subsequent brain magnetic resonance imaging redemonstrated choanal atresia with new findings of vermian hypoplasia with splaying of the cerebellar hemispheres, hypoplastic internal auditory canals, and inadequate visualization of cranial nerves VII and VIII (Fig 2). Renal involvement was excluded by urinalysis negative for proteinuria, normal renal and bladder ultrasonography findings, and normal blood pressure for age throughout admission. Review of maternal prenatal records and further history excluded the possibilities of maternal diabetes and maternal retinoic acid exposure.In the setting of multiple major criteria for CS (choanal atresia, characteristic microtia with middle/inner ear anomalies, cranial nerve palsy, and coloboma), genetics was consulted and recommended performing karyotype, chromodomain helicase 7 (CHD7, on chromosome 8q12) mutation analysis, and microarray for further evaluation. These tests were performed simultaneously and revealed a normal karyotype and microarray with specific CHD7 gene testing notable for a heterozygous known pathogenic variant for CS, c.7879 C>T, p.R2627X. (11) Up to 90% of patients with CS have mutations in the CHD7 gene. (12)(13)(14) Thus, the diagnosis of CS was confirmed based on these classic genotypic and phenotypic features.CS is a rare genetic syndrome, with an incidence of approximately 1 in 10,000 to 15,000 live births. (15) Several proposed clinical criteria for the diagnosis of CS exist. (16)(17)(18) The lack of consensus guidelines is likely a reflection of the wide phenotypic spectrum of CS. Among all 3 sets of criteria, coloboma and choanal atresia are of major diagnostic significance. These guidelines differ in their inclusion of hypoplasia of the semicircular canals (17) and cranial nerve abnormalities (16) as major criteria (see Table 1 for a comparison of diagnostic guidelines). Notably, the absence of semicircular canals has been considered to be a hallmark feature of CS not typically associated with other syndromes. (14) All criteria necessitate the presence of at least 2 major criteria and some combination of minor criteria for diagnosis (Table 1). (16)(17)(18)Pediatric otolaryngology performed endoscopic choanal atresia repair on day 6 after birth, and the patient was successfully extubated to room air immediately after the procedure. The infant had difficulty managing his secretions and poor oromotor coordination after extubation, requiring nasogastric tube feedings. Due to poor tolerance of feeds with gastroesophageal reflux, the infant ultimately required continuous feeds via a gastrostomy tube.Profound, asymptomatic hypocalcemia was noted at 24 hours after birth and did not spontaneously improve on serial repeated measurements. In a healthy patient, hypocalcemia should stimulate the secretion of parathyroid hormone, which, in turn, acts on the bones to release calcium into the bloodstream and normalize serum calcium levels. However, this patient was found to have markedly low levels of intact parathyroid hormone, suggestive of inadequate parathyroid function consistent with primary hypoparathyroidism. Due to the severity of hypocalcemia with an inadequate response to intermittent intravenous boluses of calcium, the infant required a continuous calcium infusion for several days before transitioning to oral calcium repletion therapy.In the setting of lymphopenia (defined as an absolute lymphocyte count <1,800/µL [<1.8 × 109/L] in the first year of life [1]), undetectable TRECs, and hypoplastic thymus on chest radiography, further studies were performed to characterize a potential immunodeficiency. T- and B-cell subsets, immunoglobulin (Ig) levels, and a lymphocyte enumeration panel were obtained (Table 2). Notable findings included low CD3+, CD3+CD4+, and CD3+/CD8+ T-cell subsets; elevated B-cell count; and low IgA, low-normal IgM, low IgE, and normal IgG levels. These results suggest an isolated T-cell deficiency. Although the IgM level was low, its presence suggests that B cells are functional, although it does not indicate whether class switching will occur. The normal level of IgG must be interpreted with caution because this is likely maternal in origin.Specialized flow cytometry studies were subsequently performed because severe combined immunodeficiency would require consideration of bone marrow transplant or thymic transplant. These studies confirmed that the T-cell numbers were below the tenth percentile for age. Reassuringly, the percentage of naive CD4 T cells was near normal, and the percentage of naive CD8 T cells was normal. Taken together, these findings suggest partial thymic hypoplasia rather than complete thymic aplasia. B-cell and natural killer cell populations were in the normal range on specialized flow cytometry. These findings again support the diagnosis of a T-cell immunodeficiency, which has been increasingly recognized in association with CS. (1)(19)(20) The effect of this T-cell immunodeficiency on humoral immunity will be elucidated on future laboratory studies with a lymphocyte stimulation panel and repeated immunoglobulin panels. Because of his CD4 lymphocytopenia (lymphocyte count <500/µL (<0.50 × 109/L), prophylaxis for pneumocystis pneumonia with trimethoprim-sulfamethoxazole was initiated, any necessary blood products will be irradiated and cytomegalovirus negative, and live vaccines will be avoided.Hypocalcemia and T-cell immunodeficiency are considered hallmark features of 22q11.2DS but are often overlooked features of CS. Not only are hypocalcemia and lymphopenia common in CS, they may be even more common in CS than in 22q11.2DS. (1) These overlapping phenotypic features are postulated to be secondary to the common genetic pathways involved in both syndromes. (1)(2)(19)(20)In 22q11.2DS, the 40-gene deletion encompasses the TBX1 gene, which is thought to be critical in the development of the hallmark features of the syndrome, as mutations in this gene alone result in a similar phenotype to 22q11.2DS. (21) The T-box transcription factor TBX1, encoded by the eponymous gene, regulates the expression of factors in downstream pathways involved in the genesis of the heart, thymus, parathyroid, and palate. (2)(21)(22) Much of the phenotype in 22q11.2DS is thought to result from the aberrant development of the third and fourth pharyngeal pouches, which eventually form the thymus and parathyroid gland. Thus, in 22q11.2DS, both lymphopenia and hypocalcemia are common due to the affected thymus and parathyroid.In CS, the aberrant CHD7 gene is postulated to regulate the transcription of the same end targets as the TBX1 gene. (2) Thus, CS can be associated with immunodeficiency in the setting of thymic maldevelopment. (1)(19)(20) It has been previously observed that lymphopenia is tightly associated with hypocalcemia in patients with CS, which is hypothesized to result from similarly impaired development of the third and fourth pharyngeal pouches (and thus, the thymus and parathyroid gland) as is described in 22q11.2DS. (1) Our patient was found to have hypocalcemia and lymphopenia in the setting of hypoparathyroidism and partial thymic hypoplasia, further redemonstrating this association. Therefore, as has been previously proposed, we suggest universal screening of all patients with suspected CS and/or 22q11.2DS with a complete blood cell count with differential count, lymphocyte subset panel, and calcium level. (19)(20)The phenotypic features of 22q11.2 deletion syndrome and CHARGE syndrome (CS) are not mutually exclusive; thus, both should be considered in the setting of clinical concern for either condition.Hypocalcemia and immunodeficiency, particularly T-cell immunodeficiency, are frequently associated with CS.Complete blood cell count with differential count, lymphocyte subset panel, and calcium level should be routinely included in the laboratory evaluation for patients with suspected CS or 22q11.2 deletion syndrome.We thank Dr Min Hwang for her expert review of the manuscript. We extend special thanks to the family of this patient for their willingness to share and contribute to medical education through the publication of this case review.The views expressed herein are those of the authors and do not reflect the official policy of the Department of the Army/Navy/Air Force, Department of Defense, or US Government.