From Rarity to Reality: Nivelon-Nivelon-Mabille Syndrome Presenting with Renal Tubular Acidosis

A 9-year-old girl presented with growth failure, polyuria, and polydipsia for 4 years.Physical examination revealed rachitic rosary, wrist widening, and double malleoli without facial dysmorphism.There was a family history of infantile death from severe acute malnutrition.Laboratory investigations revealed normal anion-gap metabolic acidosis, hypokalemia, alkaline urine, and hypercalciuria.On the abdominal sonogram, bilateral medullary nephrocalcinosis was seen.Clinical and laboratory features were suggestive of distal renal tubular acidosis (dRTA).To confirm the diagnosis, genetic analysis was performed, revealing a novel heterozygous variant (c.10C>T, p.Arg4ter) in exon 2 of the Hedgehog Acyltransferase (HHAT) gene, which is classified as a likely pathogenic variant by the American College of Medical Genetics.The variant was confirmed with Sanger sequencing, as shown in [Figure 1].The final diagnosis was dRTA due to Nivelon-Nivelon-Mabille syndrome (NNMS).Clinical screening of family members didn't reveal any abnormality.Parents were given genetic counseling.