A CASE OF COSTELLO SYNDROME ASSOCIATED WITH SIADH (SYNDROME OF INAPPROPRIATE ANTIDIURETIC HORMONE)

Objectives: To clarify the pathophysiological significance of SIADH (syndrome of inappropriate antidiuretic hormone) in a patient with Costello syndrome (CS) presenting disorders of water-electrolyte imbalance.

Methods: This 6-year-old boy was admitted to our hospital because of convulsive status epilepticus. He was diagnosed as CS based on clinical findings including lymphedema of legs, curly hair, unilateral ptosis, low-set ears, depressed nasal bridge, bulbous nose, pigmented skin with deep palmar and plantar creases, hyperextensibility of finger joint, mild pulmonary stenosis, feeding problems, and delays in growth and development. Routine laboratory investigations showed severe and persistent hyponatremia and hyperosmolar urine. Endocrinological studies and therapeutic trials (water restriction) were performed for the treatment of persistent hyponatremia and lymphedema of legs. Results: Endocrinological evaluation showed significant elevation of ADH at hyponatremic state, suggesting inappropriate oversecretion of ADH. In contrast, adrenocorticotropic hormone (ACTH), cortisol and growth hormone (GH) were within normal range. Brain MRI revealed cerebral atrophy but no abnormal pituitary structure. Beneficial effect of water restriction supports the diagnosis of SIADH.

Conclusion: Because of absence of complaint from severely retarded patient, we must recognize disorders of water-electrolyte imbalance that may cause convulsive status epilepticus. We here reported a case of CS presenting with SIADH probably caused seizure. Although only one case of CS with hyponatremia was reported in the literature, our patient suggests the need for careful endocrinological evaluation of cases with CS.