Inherited Type-1 renal tubular acidosis with short stature: a rare case report from Nepal.

INTRODUCTION

Distal renal tubular acidosis (dRTA), or Type-1 RTA, is a rare disorder characterized by the failure of alpha-intercalated cells in the distal nephron to excrete hydrogen ions. This leads to a normal anion gap metabolic acidosis, hypokalemia, hypercalciuria, and persistently alkaline urine. Complications include nephrocalcinosis, growth retardation, and skeletal abnormalities. Hereditary forms, often involving mutations in genes like SLC4A4, typically present in early life and may include systemic features such as sensorineural hearing loss. The present case indeed reports and summarizes both clinical symptoms and diagnosis, long-term outcomes, genetic inheritance, epidemiology, and current treatment options, with the aim of shedding more light onto this rare disorder, with a specific focus on the diagnostic challenges posed by a delayed presentation and the importance of genetic evaluation.

CASE PRESENTATION: We report a 27-year-old female with progressive lower limb weakness and chronic muscle cramps. She had a longstanding history of renal calculi since adolescence and marked growth delay. Laboratory tests revealed normal anion gap metabolic acidosis, urinary pH >7.0, hypokalemia, hypophosphatemia, and vitamin D deficiency. Imaging showed bilateral nephrocalcinosis. Genetic testing identified a pathogenic SLC4A4 mutation, confirming inherited dRTA. Treatment with potassium citrate, sodium bicarbonate, vitamin D, calcium, and iron supplementation led to significant clinical improvement.

DISCUSSION: This case highlights the diagnostic challenges of hereditary dRTA and its systemic burden. Nephrolithiasis, short stature, and persistent metabolic acidosis should prompt consideration of RTA. Although SLC4A4 is commonly linked with proximal defects, its mutation can present with distal tubular dysfunction, emphasizing the role of genetic analysis.

CONCLUSION

Hereditary dRTA is a rare but treatable condition. Early diagnosis and lifelong alkali therapy can significantly reduce complications, including chronic kidney disease and skeletal deformities. This case reinforces the need for heightened awareness among clinicians to consider dRTA in patients presenting with chronic fatigue, muscle weakness, short stature, and recurrent nephrolithiasis. Furthermore, it underscores the value of genetic evaluation in uncovering the precise etiology, allowing for tailored management and genetic counseling.