Life-threatening metabolic crises in early childhood: a rare case report

*Correspondence: [e-mail].

Abstract

Case Presentation: V.O., female, 4 months old, admitted with chronic malnutrition, anemia, edema, hypoalbuminemia and anuria. Presented with great irritability, decreased level of consciousness and seizures. Developed multiple organ dysfunction, including renal (anuria), hepatic (hepatomegaly, steatosis, enzymatic alteration), hematologic (blood dyscrasia), cardiac (severe cardiac dysfunction), neurologic (coma, seizures), and metabolic (metabolic acidosis, hyperlactatemia, hyperammonemia) impairments. Research for congenital/acquired infections, immunodeficiencies and screening for inborn errors were performed, revealing elevated serum ammonia. Expanded investigation with molecular panel of treatable diseases revealed the presence of two variants of uncertain significance in heterozygosity in the CA5A gene, responsible for encoding the 5A carbonic anhydrase.

Discussion: The carbonic anhydrase VA (CA-VA) is responsible for the generation of bicarbonate that will be available as a substrate for the urea and Krebs cycles. CA-VA deficiency is a newly described disease of early onset and should be suspected in newborns or infants with hyperammonemic metabolic encephalopathy, lethargy, diet intolerance, weight loss, tachypnea, seizures and coma. Patients usually present with normal neuropsychomotor development, with an initial metabolic crisis and subsequent stability. In acute metabolic decompensations, laboratory findings include elevated plasma ammonia, lactate, and ketones, combined with hypoglycemia in some cases. Theoretically, neonatal screening by tandem mass spectrometry may detect these changes, however the increase in these metabolites can be subtle, compared to primary enzyme defects, and present only in acute metabolic decompensation, making a false negative result. Definitive diagnosis is determined by the identification of pathogenic biallelic variants in the CA5A gene.

Final Comments: CA-VA deficiency should be considered in cases of encephalopathy with hyperammonemia and early onset hyperlactatemia, as a differential diagnosis from urea cycle defects, organic aciduria and pyruvate carboxylase deficiency. The dosage of biochemical markers may present limitations, and therefore molecular analysis of the gene should be considered in patients with suggestive clinical and biochemical findings, since the disease may be considered a partially treatable inborn error

Publication History

Article published online:
12 May 2025