ICD-10 Code A50.40 – Late congenital neurosyphilis, unspecified (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code A50.40 – Late congenital neurosyphilis, unspecified
What it is
This code identifies late neurologic complications of congenital syphilis when the specific manifestation is not documented. Use it for patients whose infection was acquired before birth and later affects the nervous system.
Clinical signs
Clinical features vary; refer to documentation. Standard references describe neurologic involvement from congenital syphilis, but the exact findings may be unclear, so you should code only what is recorded.
When to use this code
Use A50.40 when the provider documents late congenital neurosyphilis and does not name a more specific neurologic complication. It also fits when the record confirms congenital syphilis with late nervous system involvement, but details are limited. If the note gives a specific manifestation, code that instead.
Do not use for
Do not use this code for acquired neurosyphilis or for congenital syphilis without neurologic involvement. If documentation is incomplete, check documentation rather than assuming late neurosyphilis.
Coding tip
Choose the unspecified code only when the chart confirms late congenital neurosyphilis but does not support a more specific ICD-10-CM option.