Rare diseases · Sign or symptom
Anti-U1 ribonucleoprotein antibody positivity
HP:0033028
What it means
The presence autoantibodies in the serum that react to proteins (70 Kd, A, C) that are associated with U1 RNA and form U1snRNP.
High titers of anti-RNP antibodies are diagnostic of mixed connective tissue disorder (MCTD). Anti-RNP antibodies can also be found in patients with systemic lupus erythematosus.
Rare diseases that can present with this2
The range is how often this sign appears among people diagnosed with each disease — it is not a probability of having any of them. Many of these signs also occur in common, non-rare conditions, and Orphanet separately records 1 disease where this sign is specifically absent. A sign on this page is a conversation to have with a clinician, not a conclusion.
Part of the broader category
Also called: Anti-RNP-antibodies · Anti-Scl-34 antibody positivity · Anti-U1-RNP antibody positivity · Anti-U3 ribonucleoprotein antibody positivity
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Start free with EleplanThis page uses the Human Phenotype Ontology (2026-06-23) — Human Phenotype Ontology Consortium, hpo.jax.org. Disease associations from Orphanet (INSERM), CC BY 4.0. Content is educational and is not medical advice.