Type 1 SMA Linked to Increased Risk of Nephrolithiasis Among Children

Children with spinal muscular atrophy (SMA) type 1 face a heightened susceptibility to nephrolithiasis, with the most prevalent risk factors in these individuals being hypercalciuria and elevated urine specific gravity. Additionally, children with type 1 SMA and nephrolithiasis are more prone to urinary tract infections (UTIs).

These findings were published in Pediatric Neurology.

To come to these findings, researchers retrospectively examined the charts of 20 children with genetically confirmed type 1 SMA, and 13 of these patients aged between 9 and 55 months who underwent urinary tract ultrasonography were included. The retrospective analysis covered demographic and clinical characteristics, ultrasound findings, and metabolic abnormalities.

SMA | Image credit: Rochu_2008 – stock.adobe.com

They identified nephrolithiasis in 7 (54%) of the children, with 5 of them exhibiting multiple stones and the other 2 having a single stone. Kidney stone sizes varied, including 2 cases of microlithiasis defined as <3 mm, 3 with stones sized between 3 and 5 mm, and 1 with a stone larger than 8 mm, and 2 patients with nephrolithiasis also had urinary tract abnormalities. There were no statistically significant distinctions in clinical features between patients with nephrolithiasis and those without, including factors such as age, gender, body mass index-standard deviation score, prematurity, gastrostomy or tube feeding, daily water intake, or nusinersen treatment.

Children with nephrolithiasis exhibited elevated urine specific gravity (P = 0.014) and serum bicarbonate levels (P = 0.026) compared with children without nephrolithiasis. However, there were no discernible distinctions between the 2 groups concerning urine pH and serum levels of calcium, phosphorus, alkaline phosphatase, uric acid, 25-hydroxyvitamin D, or parathyroid hormone levels.

Children with nephrolithiasis were also more likely to have a history of UTIs (P = .048), which are recognized as a risk factor for nephrolithiasis. Despite UTIs being infrequent in children with SMA, factors such as reduced bladder capacity and constipation may contribute to UTIs, along with urinary incontinence. However, due to the absence of stone analysis in this study, establishing a cause-and-effect relationship between nephrolithiasis and UTIs was not feasible.

Another risk factor for childhood nephrolithiasis is urinary tract anomalies. Among the patients with nephrolithiasis, 2 exhibited urinary tract abnormalities, although neither case involved an obstructive urinary system anomaly. Because of this, these pathologies were not considered predisposing factors for nephrolithiasis.

Additionally, among the 5 children with nephrolithiasis who underwent urine metabolic evaluation, all of them exhibited hypercalciuria and 3 of them had hyperuricosuria. Meanwhile, none of them showed signs of hyperoxaluria, hypocitraturia, or hypomagnesemia.

According to the authors, hypercalciuria and elevated urine specific gravity being the 2 most common risk factors may be associated with lower fluid intake among these children.

“Determining the risk factors, increasing daily fluid intake, and medical treatment that targets metabolic abnormalities such as urine alkalinization may reduce the need for surgical intervention in type 1 SMA,” the authors said. “Considering that life expectancy has increased with developments in treatment in recent years, we believe that it is important to monitor patients in this regard and to take preventive measures.”

Looking again at kidney stones, 1 patient experienced regression of the stone with medical treatment, while the stones remained stable in 3 other patients. In one case, a 6 mm stone in the right proximal ureter was addressed through extracorporeal shock wave lithotripsy. Unfortunately, 2 patients died within 2 months of the kidney stone diagnosis.

“In conclusion, although the current study serves as a starting point for understanding this condition, it is crucial to recognize its limitations and the need for future studies with larger sample sizes and diverse patient populations,” the authors said. “A multicenter cohort study holds the potential to address these limitations and provide more comprehensive insights into the condition's characteristics, risk factors, and treatment approaches.”

Reference

Gök A, Saygılı SK, Kuruğoğlu S, Saltık S, Canpolat N. Children with type 1 spinal muscular atrophy are at increased risk for nephrolithiasis. Pediatr Neurol. 2023;150:32-36. doi:10.1016/j.pediatrneurol.2023.10.006