Early RAAS Blockade Exerts Renoprotective Effects in Autosomal Recessive Alport Syndrome

Features of Autosomal Recessive Alport Syndrome: A Systematic Review

Alport syndrome (AS) is one of the most frequent hereditary nephritis leading to end-stage renal disease (ESRD). Although X-linked (XLAS) inheritance is the most common form, cases with autosomal recessive inheritance with mutations in COL4A3 or COL4A4 are being increasingly recognized. A systematic review was conducted on autosomal recessive Alport syndrome (ARAS). Electronic databases were searched using related terms (until Oct 10th, 2018). From 1601 articles searched, there were 26 eligible studies with 148 patients. Female and male patients were equally affected. About 62% of patients had ESRD, 64% had sensorineural hearing loss (SNHL) and 17% had ocular manifestation. The median at onset was 2.5 years for hematuria (HU), 21 years for ESRD, and 13 years for SNHL. Patients without missense mutations had more severe outcomes at earlier ages, while those who had one or two missense mutations had delayed onset and lower prevalence of extrarenal manifestations. Of 49 patients with kidney biopsy available for electron microscopy (EM) pathology, 42 (86%) had typical glomerular basement membrane (GBM) changes, while 5 (10%) patients showed GBM thinning only. SNHL developed earlier than previously reported. There was a genotype phenotype correlation according to the number of missense mutations. Patients with missense mutations had delayed onset of hematuria, ESRD, and SNHL and lower prevalence of extrarenal manifestations.

A family case of X-linked Alport syndrome patients with a novel variant in COL4A5

We herein report 2 Japanese patients with X-linked Alport syndrome (XLAS), with a novel variant in COL4A5. Patient 1 was a 16-year-old Japanese girl with a history of microscopic hematuria, without proteinuria, renal dysfunction, deafness, or ocular abnormalities. At 13 years of age, renal biopsy was performed; however, a diagnosis of AS was not considered. When her mother (patient 2) was 40 years of age (3 years after patient 1 underwent a renal biopsy), patient 2 was found to have asymptomatic hematuria, proteinuria, and an increased serum creatinine level, without deafness and ocular abnormalities. Subsequently, immunofluorescence staining for alpha 5 chains of type IV collagen was performed in patient 1. Pathological findings were consistent with AS, and genetic analysis demonstrated that both patients had a heterozygous mutation in COL4A5 (NM_000495.4: exon41:c.C3769T: p.Q1257X). To date, more than 900 different COL4A5 mutations have been identified; however, this variant has not been previously described. Physicians have to consider AS when they perform a renal biopsy in all patients with hematuria despite absent/present of family history, hearing loss, and ocular abnormality. Especially, when findings of light microscopy and immunofluorescence microscope are unclear, it should be considered carefully. Electron microscopy findings are very important.