Congenital contractural arachnodactyly (Beals)

Overview

Congenital contractural arachnodactyly (CCA) is a rare inherited disorder that affects connective tissue throughout the body. Connective tissue provides strength and flexibility to various structures, including bones, joints, muscles, and blood vessels. Individuals with CCA often present with distinct physical features observable from birth, such as long, slender fingers and toes (arachnodactyly) and joints that are fixed in a bent position (contractures). The severity of these features can vary significantly among affected individuals [PMID:18451828].

Sometimes referred to as Beals syndrome, CCA is distinct from Marfan syndrome, although both conditions affect connective tissue and can share some symptoms. The underlying genetic cause helps to differentiate these conditions. CCA primarily affects growth and development, particularly of the skeletal system, and can also involve the cardiovascular system. As a rare condition, the exact number of people affected in the UK is not well established.

Symptoms & clinical features

The hallmark symptoms of CCA include multiple joint contractures that are present at birth, commonly affecting the knees, elbows, and fingers. These contractures can restrict movement to varying degrees. Another characteristic feature is arachnodactyly, which means having unusually long and thin fingers and toes, often described as 'spider-like' [PMID:28775438].

Skeletal abnormalities are common and may include a curved spine (scoliosis or kyphosis), a chest wall deformity (pectus excavatum or carinatum), and reduced bone density. Some individuals may also have ear malformations, such as 'crumpled' ears, and a distinctive facial appearance [PMID:18451828]. Cardiovascular issues, while less common than in other connective tissue disorders, can sometimes occur, such as a dilated aortic root, which is the initial part of the main artery leaving the heart.

Video: Genetics 101

Affected organs

CCA primarily affects the skeletal system, leading to features like joint contractures, arachnodactyly, and spinal curvature. The connective tissues in the joints, bones, and cartilage are most significantly impacted. The ears may also be affected, presenting with a crumpled appearance due to altered cartilage [PMID:28775438].

While less frequently, the cardiovascular system can be involved, particularly the aorta, the large blood vessel that carries blood from the heart to the rest of the body. Changes in the structure of the aortic wall can lead to dilatation. Rarely, other organs can be affected due to the widespread nature of connective tissue, but skeletal and joint issues are the most prominent concerns.

Multiple body systems

Systemic involvement

Cellular impact

Mechanism at cellular level

Risks & severity

The severity of congenital contractural arachnodactyly can vary widely, even within the same family. Some individuals may have relatively mild symptoms, while others experience more significant challenges, particularly with mobility due to severe joint contractures. The joint contractures are present from birth and can range from mild stiffness to severe limitations in movement.

Spinal curvature (scoliosis) may progress over time, sometimes requiring interventions. While most individuals with CCA have a normal lifespan, complications such as severe aortic dilatation (if present) could potentially reduce life expectancy; however, this is less common than in conditions like Marfan syndrome. Regular monitoring is important to manage potential complications and improve quality of life.

Genetic causes

Congenital contractural arachnodactyly is caused by pathogenic variants in the FBN2 gene. This gene provides instructions for making a protein called fibrillin-2, which is an important component of microfibrils. Microfibrils are critical structural elements of connective tissue, providing strength and elasticity to various body tissues.

Fibrillin-2 works alongside fibrillin-1 (encoded by the FBN1 gene, which is associated with Marfan syndrome) to form flexible fibres within the extracellular matrix, the complex network of proteins and other molecules that surrounds and supports cells in tissues. Pathogenic changes in FBN2 disrupt the normal structure and function of fibrillin-2, leading to abnormal connective tissue development and the characteristic features of CCA [PMID:16331652]. These genetic changes typically result in a reduced amount of functional fibrillin-2 protein or the production of a faulty protein.

• FBN2
  fibrillin 2

Inheritance pattern

Congenital contractural arachnodactyly follows an autosomal dominant inheritance pattern. This means that a person only needs to inherit one copy of an altered FBN2 gene from one parent to develop the condition. If a parent has CCA, there is a 50% chance with each pregnancy that their child will inherit the pathogenic gene variant and therefore the condition.

The condition can also arise spontaneously in an individual with no family history, due to a new (de novo) pathogenic variant in the FBN2 gene. In such cases, the affected individual can then pass the condition on to their children in an autosomal dominant manner.

Diagnosis & testing

Diagnosing congenital contractural arachnodactyly typically begins with a clinical evaluation of a baby or child presenting with the characteristic physical features, such as joint contractures, arachnodactyly, and crumpled ears. Imaging studies like X-rays may be used to assess skeletal abnormalities, including scoliosis and chest wall deformities.

A definitive diagnosis of CCA is confirmed through genetic testing, which looks for pathogenic variants in the FBN2 gene. In the UK, genetic testing for suspected inherited conditions like CCA is typically arranged through the NHS Genomic Medicine Service (GMS). Referral to a clinical genetics service is usually made by a GP or paediatrician, and genetic tests may be requested using the relevant R-code, facilitating a comprehensive genomic analysis to identify the underlying cause of the condition.

Management & lifestyle

Management of congenital contractural arachnodactyly focuses on addressing the specific symptoms and potential complications. Physiotherapy and occupational therapy are often recommended from an early age to improve joint mobility, manage contractures, and enhance function. In some cases, stretching exercises, splinting, or orthoses may be used.

Scoliosis may require regular monitoring and, if severe, can be managed with bracing or surgical intervention. Cardiac monitoring, including echocardiograms, may be recommended to check for aortic dilatation, although this is less common in CCA than in Marfan syndrome. Affected individuals will typically be managed by a multidisciplinary team involving paediatricians, orthopaedic surgeons, physiotherapists, and geneticists within the NHS. Genetic counselling is an important part of care, providing information about the condition, inheritance, and support for families.

UK care pathway

In the UK, individuals suspected of having genetic conditions like congenital contractural arachnodactyly would typically enter the NHS Genomic Medicine Service (GMS) pathway. This usually begins with a referral from a general practitioner or specialist to a clinical genetics service. Genetic counsellors play a crucial role within these services, offering support, information, and coordinating genetic testing.

Genetic testing for CCA involves analysis of the FBN2 gene and is conducted through accredited NHS laboratories, often guided by specific R-codes from the National Genomic Test Directory. This ensures that the most appropriate and high-quality genomic tests are used to establish a diagnosis and inform clinical management strategies.

Related conditions

When considering congenital contractural arachnodactyly, it is important to differentiate it from other connective tissue disorders that may present with similar features. Marfan syndrome is a well-known condition that also affects connective tissue and can cause long limbs, arachnodactyly, and joint hypermobility, but it is primarily caused by variants in the FBN1 gene and has a higher risk of significant cardiovascular and ophthalmological complications. Loeys-Dietz syndrome, another connective tissue disorder, shares some features but typically involves more severe arterial tortuosity and aneurysm risk.

Ehlers-Danlos syndromes, a group of conditions characterised by joint hypermobility, skin extensibility, and tissue fragility, might also be considered in a differential diagnosis. Accurate diagnosis, often through genetic testing, is key to distinguishing between these conditions and ensuring appropriate management.

Frequently asked questions