Health Library

Aase syndrome

Aase-Smith syndrome; Hypoplastic anemia - triphalangeal thumbs; Aase-Smith type; Diamond-Blackfan with AS-II; Aase-Smith I syndrome; Hydrocephalus-cleft palate-joint contractures syndrome; Aase-Smith syndrome type 1

Aase syndrome is a rare condition that involves a certain type of anemia and certain joint and skeletal deformities.

Presentation

I Would Like to Learn About:

Causes

Many cases of Aase syndrome occur without a known reason and are not passed down through families (inherited). However, some cases have been shown to be inherited. These are due to a change in 1 of 20 genes important for making protein correctly (the genes make ribosomal proteins).

This condition is similar to Diamond-Blackfan anemia, and the two conditions should be considered the same. A missing piece on chromosome 19 is found in some people with Diamond-Blackfan anemia.

The anemia in Aase syndrome is caused by poor development of the bone marrow, which is where blood cells are formed.

Symptoms

Symptoms may include:

• Absent or small knuckles
• Cleft palate
• Deformed ears
• Droopy eyelids
• Inability to fully extend the joints from birth
• Narrow shoulders
• Pale skin
• Triple-jointed thumbs

Exams and Tests

Your health care provider will perform a physical exam. Tests that may be done include:

• Bone marrow biopsy
• Complete blood count (CBC)
• X-rays

Treatment

Treatment may involve blood transfusions in the first year of life to treat anemia.

A steroid medicine called prednisone has also been used to treat anemia associated with Aase syndrome. However, it should only be used after reviewing the benefits and risks with a provider who has experience treating anemias.

A bone marrow transplant may be necessary if other treatment fails.

Outlook (Prognosis)

The anemia tends to improve with age.

Possible Complications

Complications related to anemia include:

• Fatigue
• Decreased oxygen in the blood
• Weakness

Heart problems can lead to a variety of complications, depending on the specific defect.

Severe cases of Aase syndrome have been associated with stillbirth or early death.

Prevention

Genetic counseling is recommended if you have a family history of this syndrome and wish to become pregnant.

Related Information

References

Jones KL, Jones MC, del Campo M. Limb defect as major feature. In: Jones KL, Jones MC, del Campo M, eds. Smith's Recognizable Patterns of Human Malformation. 8th ed. Philadelphia, PA: Elsevier; 2022:428-459.

National Institutes of Health. National Center for Advancing Translational Sciences. Genetic and Rare Diseases Information Center website. rarediseases.info.nih.gov/diseases/5642/aase-smith-syndrome. Updated May 2026. Accessed May 26, 2026.

Thornburg CD. Congenital hypoplastic anemia (Diamond-Blackfan anemia). In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 497.

Review Date: 7/28/2025  

Reviewed By: Anna C. Edens Hurst, MD, MS, Associate Professor in Medical Genetics, The University of Alabama at Birmingham, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

A.D.A.M., Inc. is accredited by URAC, for Health Content Provider (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics. This site complies with the HONcode standard for trustworthy health information: verify here.

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. No warranty of any kind, either expressed or implied, is made as to the accuracy, reliability, timeliness, or correctness of any translations made by a third-party service of the information provided herein into any other language.

© 1997- 2026 A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited.

All content on this site including text, images, graphics, audio, video, data, metadata, and compilations is protected by copyright and other intellectual property laws. You may view the content for personal, noncommercial use. Any other use requires prior written consent from Ebix. You may not copy, reproduce, distribute, transmit, display, publish, reverse-engineer, adapt, modify, store beyond ordinary browser caching, index, mine, scrape, or create derivative works from this content. You may not use automated tools to access or extract content, including to create embeddings, vectors, datasets, or indexes for retrieval systems. Use of any content for training, fine-tuning, calibrating, testing, evaluating, or improving AI systems of any kind is prohibited without express written consent. This includes large language models, machine learning models, neural networks, generative systems, retrieval-augmented systems, and any software that ingests content to produce outputs. Any unauthorized use of the content including AI-related use is a violation of our rights and may result in legal action, damages, and statutory penalties to the fullest extent permitted by law. Ebix reserves the right to enforce its rights through legal, technological, and contractual measures.