nonsyndromic congenital nail disorder 4 (MONDO_0008798) is any isolated congenital anonychia in which the cause of the disease is a mutation in the RSPO4 gene. Also known as: HYPONYCHIA congenita, RSPO4 isolated congenital anonychia, isolated congenital anonychia caused by mutation in RSPO4, nail disorder, nonsyndromic congenital, type 4, nonsyndromic congenital nail disorder type 4.