ESPN 51th Annual Meeting

ESPN 2018


 
Renal Tubular Acidosis Secondary to Carbonic Anhydrase 2 Deficiency
MUSTAFA KOYUN 1 ERCAN MIHCI 2 ELIF COMAK 1 SEMA AKMAN 1

1- AKDENIZ UNIVERSITY, MEDICAL FACULTY, DEPARTMENT OF PEDIATRICS, DIVISION OF PEDIATRIC NEPHROLOGY, ANTALYA, TURKEY
2- AKDENIZ UNIVERSITY, MEDICAL FACULTY, DEPARTMENT OF PEDIATRICS, DIVISION OF PEDIATRIC GENETICS, ANTALYA, TURKEY
 
Introduction:

Carbonic Anhydrase Type II Deficiency is a rare genetic disease with an autosomal recessive inheritance, with cardinal features of osteopetrosis, renal tubular acidosis (RTA) and cerebral calcification. The patients generally have features of both proximal and distal RTA. We here present a case of Carbonic Anhydrase Type II Deficiency, presenting with metabolic acidosis.

Material and methods:

A 4 year old boy was referred to our unit by finding metabolic acidosis when he was evaluating with short stature and abnormal physical appearence. He had a fracture on tibia nine months ago after a trauma. There was consanginous between the parents. His motor development was normal; however, he had mild-moderate mental retardation. Height was 92 cm (3-10p) and weight 11.7 kg (3p). He had dysmorphic features with prominent forehead, upslanting palpebral fissures, triangular face, clinodactyly and hypothenar atrophy.

Results:

GFR was normal. Na:137 meq/L, K:3.8 meq/L, Cl 111 meq/L. Calcium, phosphorus and ALP was normal; pH 7.21, bicarbonate 15.9 mmol/L. Serum anion gap was normal. Urine pH 6.5, no glucosuria or proteinuria. Urine calcium excretion and tubular phosphate reabsorbtion was also normal. No nephrocalcinosis or nephrolithiasis on ultrasonograhy. Urine anion gap was positive, suggesting distal RTA. A response to furosemid test was seen, suggesting proximal RTA. On X-ray, bone density is increased, compatible with osteopetrosis. Cerebral calcification was not present. A genetic analysis revealed that he had a homozygous mutation on enzyme carbonic anhydrase 2 (c.188 189 ins G, p.G63fs71X). Type 3 RTA secondary to carbonic anhydrase deficiency was diagnosed.

Conclusions:

Carbonic Anhydrase Type II Deficiency should be suspected in a patient with RTA, not classified as proximal or distal type, and having dysmorphic features with osteopetrosis.