Prolidase deficiency: a patient without hydroxyproline-containing iminodipeptides in urine

Area of Science:

• Biochemistry
• Genetics
• Pediatric Medicine

Background:

• Prolidase deficiency is a rare autosomal recessive disorder.
• It results from mutations in the proline dipeptidase (PEPD) gene, leading to impaired collagen breakdown.
• Clinical manifestations typically include recurrent infections, skin abnormalities, and developmental delays.

Observation:

• A 17-year-old female presented with biochemical evidence of prolidase deficiency.
• Urine analysis revealed significant accumulation of proline-containing dipeptides.
• Plasma and erythrocyte assays showed a near-complete absence of prolidase enzyme activity.

Findings:

• The patient's biochemical profile confirmed prolidase deficiency.
• Notably, unlike previously reported cases, this patient did not excrete hydroxyproline-containing dipeptides in her urine.
• This atypical finding suggests potential variability in the clinical or biochemical phenotype of prolidase deficiency.

Implications:

• This case highlights the importance of comprehensive dipeptide analysis in diagnosing prolidase deficiency.
• The absence of hydroxyproline-containing dipeptides may indicate a specific mutation or a milder biochemical phenotype.
• Further research is warranted to understand the full spectrum of prolidase deficiency and its genotype-phenotype correlations.