Is C1q nephropathy associated with a WDR19 gene mutation? A case report

Area of Science:

• Nephrology
• Genetics
• Rare Diseases

Background:

• Complement 1q nephropathy (C1qN) remains underrecognized despite its description in 1985, owing to its low prevalence (0.2-2.5%) and limited clinical emphasis.
• Early diagnosis of C1qN is crucial as it can present with severe renal injury.

Observation:

• A 50-year-old woman presented with incidental non-nephrotic proteinuria and normal glomerular filtration rate.
• Renal biopsy demonstrated C1qN with significant fibrosis.
• Family history revealed consanguinity and kidney diseases, prompting genetic investigation.

Findings:

• Genetic analysis identified a homozygous c.991G>T (p.G331C) mutation in the WD-repeat domain 19 (WDR19) gene.
• The same mutations were found in relatives with kidney conditions, confirming a genetic link.
• Treatment with methylprednisolone and mycophenolate mofetil led to partial remission over one year.

Implications:

• This case underscores the necessity of prompt renal biopsy in patients with non-nephrotic proteinuria to detect severe kidney injury.
• Investigating WDR19 gene mutations is vital for understanding C1qN pathogenesis.
• This report details the first adult case of C1qN diagnosed in Turkey, contributing to the limited literature on this rare condition.