Alport syndrome (AS) is an inherited disease caused by a mutation in type IV collagen genes, including the COL4A3 COL4A4 and COL4A5 genes. X-linked Alport syndrome associated with a mutation in COL4A5 gene is the most commonly observed type of AS. The clinical symptoms of AS include renal, hearing and vision impairments. The diagnosis is based on the manifestation of these symptoms and either specific kidney biopsy lesions or positive genetic tests. We present a case of a de novo biopsy negative Alport syndrome. The patient’s diagnosis was delayed because the biopsy did not show specific findings for AS. Genetic tests (Next-Gen Sequencing, NGS) made it possible to establish the final correct diagnosis. A c.2441G>A variant of COL4A5 gene detected in probant has not been described in the literature yet. In the past years a significance of NGS in AS diagnosis has increased. The new pathogenic variants are still being reported including de novo mutations having an incidence rate of around 12%. Early diagnosis is crucial for the effective treatment of patients with AS.