[Type I Hyperprolinemia - What about the Kidney?]

Hyperprolinemia is a rare genetic condition due to mutations in proline metabolic pathway. Type I Hyperprolinemia (HPI) typically causes neuropsychiatric disorders, and diagnosis is usually confirmed in pediatric population with suggestive neuropsychiatric involvement by elevated serum proline levels and elevated urinary proline, hydroxyproline, and glycine levels. The possible coexistence of nephropathy in patients with HPI, often specified as malformative urinary disease, is often mentioned. However, reports of HPI diagnosis due to kidney impairment do not exist in scientific literature yet. Here we present the case of a patient presenting with chronic kidney disease secondary to obstructive nephropathy who received a HPI diagnosis in adulthood. Interestingly, the family study showed the same 22q11.21 deletion and elevated blood proline levels in the father, who had no clinical anomalies. We therefore suggest, in light of the high frequency of mutations involving 22q11 and PRODH in the general population, to consider these rare alterations in patients with congenital urinary malformations, even in the presence of nuanced neurological symptoms and negative family history.