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Brachydactyly type C
This inherited condition primarily affects the middle segments of fingers and the bones connecting thumbs to the wrists. Individuals typically have shortened fingers with a distinctive pattern, though function is usually preserved. The condition is present from birth and does not worsen over time.
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Overview
Brachydactyly type C represents a specific pattern of skeletal limb malformation affecting the hands and occasionally feet. The term brachydactyly describes shortened digits, and type C refers to a particular pattern where the middle bones of fingers (middle phalanges) are markedly shortened or sometimes absent, combined with shortening of the first metacarpal bones that form the palm portion of the thumbs. This condition belongs to a broader family of brachydactyly subtypes, each with distinct skeletal features and genetic causes.
The condition is rare, though exact prevalence figures across the UK population are not well established. Most individuals with brachydactyly type C lead typical lives with minimal functional limitation, as the shortening primarily affects appearance rather than hand mechanics. The condition follows an autosomal dominant inheritance pattern, meaning a pathogenic variant in a single copy of the causative gene is sufficient to produce the skeletal changes.
Symptoms & clinical features
The hallmark clinical feature is shortening of the middle phalanges across multiple fingers, most notably affecting the index, middle, and ring fingers. In some individuals, these middle finger segments may be extremely short or appear to be absent altogether, causing the affected fingers to have only two visible segments instead of the typical three. The thumb metacarpals are also characteristically shortened, which may make thumbs appear stubbier than usual.
Some affected individuals also show shortening of certain foot bones, though this is less consistent than the hand findings. The shortening is typically symmetrical, affecting both hands similarly. Despite the altered skeletal structure, most people retain good hand function and dexterity. The condition is present from birth and does not progress or worsen with age, as the skeletal pattern is established during foetal development.
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Affected organs
Brachydactyly type C primarily affects the skeletal system, specifically the small bones of the hands and occasionally the feet. The middle phalanges of fingers and the first metacarpal bones are the most consistently involved structures. Unlike some other skeletal conditions, brachydactyly type C does not typically affect other organ systems or cause internal medical complications. The changes are confined to limb bones and do not involve the skull, spine, or long bones of arms and legs.
Risks & severity
The condition is generally mild in terms of functional impact. Most individuals experience no significant disability and can perform daily activities without limitation. Hand function, including grip strength and fine motor skills, is typically preserved despite the altered bone structure. There is no association with reduced life expectancy or systemic health complications.
Severity can vary somewhat between affected individuals, even within the same family. Some may have more pronounced shortening than others, and the degree of thumb involvement can differ. However, the overall pattern remains consistent, and the condition does not evolve or deteriorate over an individual's lifetime.
Genetic causes
Brachydactyly type C results from pathogenic variants in GDF5, which encodes growth differentiation factor 5. This protein belongs to the transforming growth factor beta superfamily and plays a crucial role during skeletal development, particularly in forming the cartilage templates that later ossify into bones. GDF5 is especially important for development of the joints between bones and the growth of specific skeletal elements in the limbs.
When GDF5 function is disrupted by pathogenic variants, the normal signalling cascade that directs cartilage and bone formation in developing limbs is altered. This particularly affects certain bones that are especially dependent on GDF5 activity during foetal development, notably the middle phalanges and first metacarpals. The specific skeletal pattern seen in brachydactyly type C reflects the particular developmental windows and anatomical sites where GDF5 activity is most critical.
- GDF5 growth differentiation factor 5The GDF5 gene, or growth differentiation factor 5, is crucial for proper skeletal development, particularly influencing joint formation and bone growth.
Inheritance pattern
Brachydactyly type C follows an autosomal dominant pattern of inheritance. This means a pathogenic variant in just one of the two GDF5 gene copies is sufficient to cause the condition. Each child of an affected parent has a 50% chance of inheriting the variant and therefore developing the same skeletal pattern.
Because the condition is dominant, it typically appears in every generation of an affected family, passed from parent to child. However, new pathogenic variants can also arise spontaneously, meaning some individuals have no family history. The severity of features can vary between family members who carry the same variant, though the overall pattern remains recognisable.
Each child has a 50% chance of inheriting the pathogenic variant, regardless of sex.
Diagnosis & testing
Diagnosis of brachydactyly type C is typically made through clinical examination and radiographic imaging. X-rays of the hands clearly demonstrate the characteristic shortening of middle phalanges and first metacarpals, confirming the specific brachydactyly subtype. Genetic testing can identify pathogenic variants in GDF5, providing molecular confirmation of the diagnosis.
In the UK, individuals with suspected brachydactyly type C may be referred to clinical genetics services for evaluation. Confirmation through genetic testing can be valuable for family planning and to distinguish this condition from other skeletal dysplasias. NHS genetic testing for skeletal conditions is available through regional genomic laboratory hubs following appropriate clinical referral.
Management & lifestyle
Management of brachydactyly type C focuses primarily on monitoring and addressing any functional concerns. Most affected individuals require no specific medical intervention, as hand function is typically well preserved. For children, regular developmental monitoring ensures that fine motor skills progress appropriately despite the altered skeletal structure.
In rare instances where skeletal changes cause functional limitation or significant cosmetic concern, referral to specialist hand surgeons with expertise in congenital hand differences may be considered. However, surgical intervention is uncommon given the generally good functional outcomes. Families benefit from access to genetic counselling to understand inheritance patterns and recurrence risks for future pregnancies.
UK care pathway
In the UK, individuals with suspected brachydactyly type C are typically managed through a combination of paediatric orthopaedics and clinical genetics services. Referral pathways vary by region but generally involve initial assessment by a paediatrician or GP, followed by referral to specialists if genetic confirmation or family counselling is needed. The NHS Genomic Medicine Service provides access to genetic testing through regional genomic laboratory hubs, with testing coordinated by clinical genetics teams.
Genetic counsellors play an important role in helping families understand the inheritance pattern, recurrence risks, and implications for other family members. PanelApp includes skeletal dysplasia gene panels that encompass GDF5, facilitating appropriate diagnostic testing when clinically indicated.
Frequently asked questions
Will my child's fingers grow normally as they get older?
The skeletal pattern of brachydactyly type C is established during development before birth and does not change as children grow. Affected bones will grow proportionally but remain shorter than typical, maintaining the same relative pattern throughout life.
Will brachydactyly type C affect my child's ability to write or play sports?
Most individuals with brachydactyly type C have good hand function and can participate fully in activities including writing, sports, and musical instruments. The shortened bones typically do not prevent normal grip or dexterity.
If I have brachydactyly type C, what is the chance my children will inherit it?
Because the condition follows autosomal dominant inheritance, each of your children has a 50% chance of inheriting the genetic variant and developing the same skeletal features.
Are there any health complications associated with brachydactyly type C?
Brachydactyly type C affects only the skeletal structure of hands and occasionally feet, without associated internal organ or systemic health problems. Life expectancy and overall health are not affected by this condition.
References
- Burgess RC. Brachydactyly type C. The Journal of hand surgery. 2001. PMID: 11172365
- Robin NH, Gunay-Aygun M, Polinkovsky A. Clinical and locus heterogeneity in brachydactyly type C. American journal of medical genetics. 1997. PMID: 9024575
- Al-Qattan MM. Genetics, Clinical Presentation, Radiological Features, and Midterm Outcome of Closing Wedge Osteotomy in Children With Brachydactyly Type C. Annals of plastic surgery. 2022. PMID: 35502951
- Farooq M, Nakai H, Fujimoto A. Characterization of a novel missense mutation in the prodomain of GDF5, which underlies brachydactyly type C and mild Grebe type chondrodysplasia in a large Pakistani family. Human genetics. 2013. PMID: 23812741
- Schwabe GC, Türkmen S, Leschik G. Brachydactyly type C caused by a homozygous missense mutation in the prodomain of CDMP1. American journal of medical genetics. Part A. 2004. PMID: 14735582
- Stange K, Ott CE, Schmidt-von Kegler M. Brachydactyly Type C patient with compound heterozygosity for p.Gly319Val and p.Ile358Thr variants in the GDF5 proregion: benign variants or mutations? Journal of human genetics. 2015. PMID: 25994865
- Everman DB, Bartels CF, Yang Y. The mutational spectrum of brachydactyly type C. American journal of medical genetics. 2002. PMID: 12357473
- Zguricas J, Bakker WF, Heus H. Genetics of limb development and congenital hand malformations. Plastic and reconstructive surgery. 1998. PMID: 9514351