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Abstract: SA-PO1031

Neonatal Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) Associated with Hypothalamic Malformation in a Patient with Chromosome 1q21.1 Deletion Syndrome

Session Information

Category: Fluid, Electrolytes, and Acid-Base

  • 702 Water/Urea/Vasopressin, Organic Solutes


  • Alzarka, Bakri, Children's National Medical Center, Washington, District of Columbia, United States
  • Usala, Rachel Leigh, MedStar Georgetown University Hospital, Washington DC, District of Columbia, United States
  • Ahn, Sun-Young, Children's National Medical Center, Washington, District of Columbia, United States

Chromosome 1q21.1 deletion syndrome (OMIM 612474) is associated with a wide range of clinical abnormalities including mental retardation, microcephaly, autism, cardiac abnormalities, and cataracts.
SIADH, caused by impaired water excretion, can develop from various conditions including tumors, central nervous system disorders, medications, pulmonary disease, hypothyroidism, and glucocorticoid deficiency. To our knowledge, it has not yet been reported in association with chromosome 1q21.1 deletion syndrome.


A 6 week-old, former 34-week gestational age, female was noted to have hyponatremia (serum sodium 128 mmol/L) shortly after birth. Clinical evaluation showed a low serum osmolality, relatively high urine osmolality and urine sodium, and a significantly elevated plasma arginine vasopressin (AVP) level (32.7 pg/ml, normal 1-11). With the absence of any clinical evidence of volume depletion or any other cause of hyponatremia including renal, thyroid or adrenal dysfunction, these findings were consistent with a diagnosis of SIADH. Her exam also showed microcephaly and situs inversus with dextrocardia. Microarray results were consistent with chromosome 1q21.1 deletion syndrome. Her brain MRI revealed multiple anomalies, including posterior/inferior hypothalamic malformation with hypoplastic mammillary bodies and a markedly diminutive posterior pituitary hyperintensity on T1-weighted images, which may reflect abnormal release of AVP from the posterior pituitary gland. The patient had a partial response to fluid restriction, furosemide, and sodium supplementation. However, tolvaptan initiation resulted in effective normalization of the patient’s serum sodium level.


We report an unusual case of congenital SIADH associated with hypothalamic malformation in a neonate with chromosome 1q21.1 deletion syndrome. Our findings suggest that congenital hypothalamic/pituitary malformations should be considered as a cause of SIADH in patients with phenotypic findings consistent with chromosome 1q21.1 deletion syndrome. In addition, tolvaptan may provide an effective therapeutic option for infants with SIADH.