Background: Inherited renal hypomagnesemia is rare but may indicate an underlying genetic condition, and it should be considered when evaluating unexplained hypomagnesemia. 17q12 deletion syndrome, a recurrent microdeletion including HNF1B (hepatocyte nuclear factor 1 beta) and neighboring genes such as LHX1 (LIM homeobox 1) and ACACA (acetyl-CoA carboxylase alpha), is associated with renal magnesium wasting, neurodevelopmental deficits, and multi-organ involvement. However, spinal cord anomalies, particularly syringomyelia, have not been reported to date.
Case presentation: A 12-year-old girl was referred to our pediatric nephrology department with frequent urination. Her medical history included neurodevelopmental delay, scoliosis, and behavioral abnormalities. Laboratory tests showed a serum magnesium level of 1.5 mg/dL and an elevated fractional urine magnesium excretion of 4.1%. Serum glucose, aspartate transaminase, and alanine transaminase were mildly elevated. There were no structural anomalies on urinary ultrasound and cranial magnetic resonance imaging (MRI). Radiological investigations revealed thoracolumbar scoliosis on spinal X-ray and a central syrinx extending from T3 to T6 levels on thoracic spinal MRI. Chromosomal microarray analysis identified a 1.4 Mb deletion at chromosome 17q12, which contains the HNF1B gene, confirming the diagnosis of 17q12 deletion syndrome. Oral magnesium supplementation was initiated, and the patient was referred to a multidisciplinary care team.
Conclusions: This case highlights the importance of considering genetic etiologies, particularly 17q12 deletion syndrome, in children presenting with persistent hypomagnesemia and neurodevelopmental delay. Recognizing electrolyte imbalances, despite the absence of renal structural abnormalities, and identifying coexisting spinal cord anomalies, such as syringomyelia, may guide timely genetic evaluation and enable earlier diagnosis.
Keywords: 17q12 deletion; HNF1B; case report; hypomagnesemia; syringomyelia.