What causes Aase syndrome?
Last updated September 6, 2026.
Aase syndrome is caused by a genetic change in genes that help cells build ribosomes, which affects red blood cell production and thumb development before birth. Ribosomes assemble protein inside every cell, and when the genes that build them are altered, the fastest growing tissues in a developing baby are affected first. That is why the two hallmark features are anemia that shows up in the first months of life and thumbs with three bones instead of the usual two. Most specialists now consider Aase syndrome part of the Diamond-Blackfan anemia spectrum, where changes in ribosomal protein genes such as RPS19 are frequently found. In many families the genetic change is new in the child, so there is no history of it in parents or siblings, and nothing a parent ate, took, or did during pregnancy brings it on. Care works best when a hematologist follows the blood counts and a genetics team looks at the whole picture, including a hand surgeon when thumb function limits daily tasks.
What to do
- Ask for genetic testing: A gene panel covering ribosomal protein genes can confirm the diagnosis and guide what to expect for siblings and future pregnancies.
- Track the blood counts: Keep a copy of each complete blood count so your hematologist can see the trend rather than a single result.
- Know the anemia signs: Unusual paleness, low energy, poor feeding, or fast breathing in an infant are reasons to call the care team the same day.
- Map the family history: Write down any relatives with early anemia, unusual thumbs, or short stature and bring that list to the genetics visit.
- Plan hand function early: Ask about a hand surgery referral if a triphalangeal thumb makes gripping, writing, or self-feeding difficult.
- See a clinician for diagnosis: Anemia plus thumb differences needs in-person evaluation; no online answer can confirm or rule out this condition for your child.
Related questions
- Can i see what my doctor wrote about me
- How do i find out what my insurance covers
- What age should i start mammograms
- What are clots in period blood