Psoriasis is a chronic inflammatory dermatosis with complex genetic basis supported by family investigation. Renal involvement in psoriasis is sparsely studied and its pathogenesis is still unclear.
We describe the case of a 7-year-old boy presented new onset of nephropathy two weeks after a flare-up of psoriasis. His mother had a long history of psoriasis without abnormal urinalysis records. The case showed non-nephrotic range proteinuria, microscopic hematuria without any other abnormal results including renal function, complement cascade, and ultrasound. Renal pathological demonstrated the diagnosis of C3 glomerulonephritis (C3GN) showing mesangial proliferative glomerulonephritis with C3 staining only, effacement of podocyte process and intramembranous electron dense deposit by electric microscopy. Parent-child trio WES performed to screening the common variants of psoriasis susceptibility locus and also the rare variants associated with C3GN. We identified a missense single nucleotide polymorphism of CARD14 (*607211, rs34367357, p.Val585Ile) carried by the proband and his mother. Meta-analysis proved the association of rs34367357 and psoriasis (p = 0.006, OR = 1.23). A hemizygouse mutation of CLCN5 (*300008, c.1904A＞G,p.Asn635Ser) was identified for diagnosis of Dent disease (*300009).
The case highlights the genetic study is necessary to facilitate disease differentiation in new onset of nephropathy with psoriasis in children.

The most frequent cause of familial glomerular hematuria is thin basement membrane nephropathy (TBMN) caused by germline COL4A3 or COL4A4 gene mutations. Less frequent but important cause with respect to morbidity is Alport syndrome caused by germline COL4A5 gene mutations. The features of Alport syndrome include hematuria, proteinuria and all males with X-linked disease and all individuals with recessive disease will develop end stage renal disease, usually at early youth. In X-linked Alport syndrome, a clear genotype-phenotype correlation is typically observed in men. Deleterious COL4A5 mutations are associated with a more severe renal phenotype and more frequent high-frequency sensorineural hearing loss and ocular abnormalities. Less severe COL4A5 mutations result in a milder phenotype, with less frequent and later onset extrarenal anomalies. The phenotype in females is highly variable, mostly due to inactivation of one of the X chromosomes. Isolated cases may be caused by de novo COL4A5 mutations or by gonosomal mosaicism. Untreated autosomal recessive Alport syndrome, caused by COL4A3 and COL4A4 mutations, is typically associated with ESRD at the age of 23-25 years and extrarenal symptoms in both men and women. The TBMN phenotype is associated with heterozygous carriers of COL4A3, COL4A4 mutations. Molecular genetic testing is the gold standard for diagnosing these diseases. Although genotype-phenotype correlations exist, the phenotype is influenced by modifying factors, which remain mainly undefined. No therapy is available that targets the cause of Alport syndrome; angiotensin-converting enzyme inhibitor therapy delays renal failure and improves lifespan.