P0871 - An A-Tip-ical Side Effect of Lithium

Background
Lithium is an FDA-approved mood-stabilizer used in treatment of bipolar disorder in children as young as 12 years old. Though seemingly effective in pediatric population for treatment of mania and mood stabilization in bipolar disorder, lithium requires frequent monitoring for toxicity and adverse side effects.

Case
An 18 year old male with Hashimoto’s thyroiditis, bipolar I disorder, depression, and anxiety, presented with 10 days of swelling, weight gain, progressive abdominal pain, emesis, diarrhea, and decreased urine output with frothy urine. Home medications included levothyroxine, Risperdal, and lithium. Creatinine was 1.2 mg/dl, increased from a baseline of 0.8 mg/dl. There was nephrotic-range proteinuria, with spot urine protein /creatinine ratio of 9. Serum lithium level was 2.5 mmol/L (therapeutic range 1-1.2 mmol/L). The renal biopsy demonstrated a tip variant focal segmental glomerulosclerosis (FSGS), with diffuse fusion of foot processes by electron microscopy, but no tubular epithelial changes. Lithium was discontinued, and the patient underwent diuresis with Lasix/albumin infusions. Proteinuria resolved within two months of medication discontinuation and he remains remission. The bipolar disorder is now treated with Lamictal and Risperdal.

Discussion and Conclusion
Lithium has a wide side effect profile, requiring close monitoring. Lithium-induced nephrotic syndrome is a well-documented, idiopathic side effect. Most renal biopsies reveal histology consistent with minimal change disease; however, FSGS has been less commonly shown to be associated with lithium use. To our knowledge, this is the first documented case of tip variant associated FSGS in a teenager. While lithium may have induced nephrosis, the subsequent decrease in glomerular filtration rate due to low effective circulating volume in nephrotic syndrome likely led to poor excretion of lithium, resulting in toxic levels and protracted recovery from its adverse side effects. Despite the atypical histopathology, our patient followed a favorable course once lithium was discontinued and remains in remission without immunosuppressive therapy.