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The combined use of Adrenocorticotropic hormone (ACTH) and Calcineurin inhibitor (CNI) in the treatment of Refractory Nephrotic Syndrome in a child

Amirtha Chinnadurai, Julie E. Goodwin

Background: Primary podocytopathies including Focal Segmental Glomerulosclerosis (FSGS) have been recognized to show variable responses to conventional treatment and overall prognosis. Persistent failure to respond to therapies remains a vexing problem for clinicians. ACTH has recently resurged as a therapy for treatment-resistant podocytopathies. We describe a case of steroid-resistant NS in a 10-year-old boy with a history of multiple failed secondary therapies, who showed partial response to biweekly ACTH therapy. Further clinical improvement was observed with the addition of the calcineurin inhibitor (CNI), tacrolimus.

Case description: A 10-year-old Hispanic boy, diagnosed with frequently-relapsing steroid sensitive NS at the age of 2, and was largely relapse-free for 5 years on Cyclosporine A (CsA). Within two months after a trial off CsA, he relapsed. His course was complicated by more frequent relapses and steroid resistance. Renal biopsy performed at this time showed early focal segmental glomerulosclerosis (FSGS) and no signs of CsA-induced nephropathy. Whole exome sequencing revealed a heterozygous variant of uncertain significance in PLCE1 (Phospholipase C Epsilon 1). Trials of the steroid sparing agents tacrolimus and mycophenolate mofetil, both with and without steroids, were ineffective. He had several prolonged hospitalizations due to poorly controlled relapse. He became dependent on biweekly 25% albumin infusions. His renal function deteriorated from a baseline creatinine of 0.3 mg/dl to 0.7 mg/dl due to multiple episodes of acute kidney injury. ACTH initiated at a low dose of 40 units/1.73 m² biweekly was ineffective. Three months later, the dose was increased to 80 units/1.73 m² biweekly and he achieved partial remission and renal function returned to baseline. Tacrolimus was added at 6 months for synergy with trough levels maintained between 3-5 ng/ml. He achieved partial remission, and avoided further hospitalizations.

Conclusion: ACTH alone or in combination with calcineurin inhibitor (CNI) can be a viable alternative for children who are resistant to other therapies. Variability in renal phenotype has been implicated with the PLCE1 (Phospholipase C Epsilon 1) gene. In this case, we suspect the role of his heterozygous variant PLCE1 mutation, or likely a compound heterozygous state with another unidentified mutation or modifiers or environmental factors, plays a role in the progression to a refractory NS state.