Distal renal tubular acidosis in a pediatric patient with ATP6V1B1 mutation

Distal renal tubular acidosis (dRTA) is a very rare disease characterized by metabolic acidosis, hypokale-mia and nephrocalcinosis caused by the impaired H+ secretion in the distal convoluted tubules of the kidney.We report the case of a one-year-old girl who firstly presented to another facility at the age of two months with insidious lack of appetite, weight loss, diarrhea, vomiting and fever, interpreted as acute gastroenteri-tis. Three weeks later she presented to our institution. Physical examination indicated altered general con-dition, severe dehydration, skin pallor, generalized hypotonia and weight for length ratio beneath the 1st percentile. Laboratory investigations showed normochromic, microcytic anemia, mild inflammatory syn-drome, decompensated metabolic acidosis, hypokalemia and hypercalcemia. Rehydration therapy was ini-tiated. Renal ultrasonography showed bilateral nephrocalcinosis, while cerebral ultrasonography revealed subarachnoid space enlargement. Although her general condition improved under treatment and the vom-iting remitted while she gained weight, the metabolic acidosis and electrolyte imbalance persisted and as-sociated alkaline polyuria. A hearing test was performed and mild sensorineural hearing loss was discov-ered. Moreover, the genetic investigation (Next Generation Sequencing) revealed that the patient is homo-zygous for ATP6V1B1 c.242T>C, p.(Leu81Pro), a pathogenic variant suggestive for dRTA. Primary dRTA, while rare, can have great impact on the patient’s quality of life. Therefore, it must be rec-ognized as quickly as possible in order to avoid complications that can ultimately lead to irreversible kidney damage.