Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy, commonly known as CARASIL, is an inherited condition that causes stroke and other impairments.

Abnormalities affecting the brain and other parts of the nervous system become apparent in an affected person's twenties or thirties. Often, muscle stiffness (spasticity) in the legs and problems with walking are the first signs of the disorder. About half of affected individuals have a stroke or similar episode before age 40. As the disease progresses, most people with CARASIL also develop mood and personality changes, a decline in thinking ability (dementia), memory loss, and worsening problems with movement.

Other characteristic features of CARASIL include premature hair loss (alopecia) and attacks of low back pain. The hair loss often begins during adolescence and is limited to the scalp. Back pain, which develops in early to mid-adulthood, results from the breakdown (degeneration) of the discs that separate the bones of the spine (vertebrae) from one another.

The signs and symptoms of CARASIL worsen slowly with time. Over the course of several years, affected individuals become less able to control their emotions and communicate with others. They increasingly require help with personal care and other activities of daily living; after a few years, they become unable to care for themselves. Most affected individuals die within a decade after signs and symptoms first appear, although few people with the disease have survived for 20 to 30 years.

CARASIL appears to be a rare condition. It has been identified in about 50 people, primarily in Japan and China.

CARASIL is caused by mutations in the HTRA1 gene. This gene provides instructions for making an enzyme that is found in many of the body's organs and tissues. One of the major functions of the HTRA1 enzyme is to regulate signaling by proteins in the transforming growth factor-beta (TGF-β) family. TGF-β signaling is essential for many critical cell functions. It also plays an important role in the formation of new blood vessels (angiogenesis).

In people with CARASIL, mutations in the HTRA1 gene prevent the effective regulation of TGF-β signaling. Researchers suspect that abnormally increased TGF-β signaling alters the structure of small blood vessels, particularly in the brain. These blood vessel abnormalities (described as arteriopathy) greatly increase the risk of stroke and lead to the death of nerve cells (neurons) in many areas of the brain. Dysregulation of TGF-β signaling may also underlie the hair loss and back pain seen in people with CARASIL, although the relationship between abnormal TGF-β signaling and these features is less clear.

Genetic Testing Information

• Genetic Testing Registry: CARASIL syndrome

Genetic and Rare Diseases Information Center

• Cerebral autosomal recessive arteriopathy-subcortical infarcts-leukoencephalopathy

Patient Support and Advocacy Resources

• National Organization for Rare Disorders (NORD)

Catalog of Genes and Diseases from OMIM

• CEREBRAL ARTERIOPATHY, AUTOSOMAL RECESSIVE, WITH SUBCORTICAL INFARCTS AND LEUKOENCEPHALOPATHY 2; CARASIL2

Scientific Articles on PubMed

• PubMed

• Fukutake T. Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL): from discovery to gene identification. J Stroke Cerebrovasc Dis. 2011 Mar-Apr;20(2):85-93. doi: 10.1016/j.jstrokecerebrovasdis.2010.11.008. Epub 2011 Jan 7. Citation on PubMed
• Hara K, Shiga A, Fukutake T, Nozaki H, Miyashita A, Yokoseki A, Kawata H, Koyama A, Arima K, Takahashi T, Ikeda M, Shiota H, Tamura M, Shimoe Y, Hirayama M, Arisato T, Yanagawa S, Tanaka A, Nakano I, Ikeda S, Yoshida Y, Yamamoto T, Ikeuchi T, Kuwano R, Nishizawa M, Tsuji S, Onodera O. Association of HTRA1 mutations and familial ischemic cerebral small-vessel disease. N Engl J Med. 2009 Apr 23;360(17):1729-39. doi: 10.1056/NEJMoa0801560. Citation on PubMed
• Oide T, Nakayama H, Yanagawa S, Ito N, Ikeda S, Arima K. Extensive loss of arterial medial smooth muscle cells and mural extracellular matrix in cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL). Neuropathology. 2008 Apr;28(2):132-42. doi: 10.1111/j.1440-1789.2007.00864.x. Epub 2007 Nov 6. Citation on PubMed
• Onodera O, Nozaki H, Fukutake T. HTRA1 Disorder. 2010 Apr 27 [updated 2019 Nov 7]. In: Adam MP, Bick S, Mirzaa GM, Pagon RA, Wallace SE, Amemiya A, editors. GeneReviews(R) [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2026. Available from http://www.ncbi.nlm.nih.gov/books/NBK32533/ Citation on PubMed