Brachydactyly type B
Definition[edit | edit source]
Brachydactyly type B (BDB) is a condition characterized by incomplete development (hypoplasia) or absence of the outermost bones of the fingers and toes (distal phalanges) and nails.
Epidemiology[edit | edit source]
This is a rare hand malformation with only a few published pedigrees in the world literature.
Types[edit | edit source]
There are 2 types of this condition, designated as type 1 and 2.
Cause[edit | edit source]
BDB type 1 is caused by mutations in the ROR2 gene. BDB type 2 is caused by mutations in the NOG gene.
Inheritance[edit | edit source]
Inheritance of both types is autosomal dominant.
Signs and symptoms[edit | edit source]
- There is absence or hypoplasia of the terminal parts of the index to little fingers with complete absence of fingernails.[1].
- The thumbs are always intact but frequently show flattening, splitting or duplication of the distal phalanges.
- Digits are less severely affected on the radial side of the hand compared to those on the ulnar side.
- The feet are similarly but less severely affected.
- The deformity is symmetric.
- There is soft tissue syndactyly, symphalangism, carpal and/or tarsal fusions and shortening of metacarpals and/or metatarsals.
For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed.
80%-99% of people have these symptoms
- 2nd-5th toe middle phalangeal hypoplasia(Underdeveloped 2nd-5th middle toe bones)
- Absent fingernail
- Aplasia/Hypoplasia of the distal phalanges of the hand(Absent/small outermost finger bone of the hand)
- Short distal phalanx of finger(Short outermost finger bone)
- Short foot(Short feet)
- Short metacarpal(Shortened long bone of hand)
- Type B brachydactyly
30%-79% of people have these symptoms
- Absent phalangeal crease
- Aplasia/Hypoplasia of the distal phalanges of the toes(Absent/small outermost bones of toe)
- Aplasia/Hypoplasia of the middle phalanges of the hand(Absent/small middle finger bone of the hand)
- Aplasia/Hypoplasia of the middle phalanges of the toes(Absent/small middle bones of toe)
- Aplasia/Hypoplasia of the nails(Absent/small nails)
- Cutaneous finger syndactyly(Webbed fingers)
- Cutaneous syndactyly of toes(Webbed skin of toes)
- Proximal placement of thumb(Attachment of thumb close to wrist)
- Tarsal synostosis(Fused ankle bones)
5%-29% of people have these symptoms
- Broad hallux phalanx(Broad bone of big toe)
- Finger syndactyly
- Hypermetropia(Farsightedness)
- Sensorineural hearing impairment
- Symphalangism affecting the phalanges of the hand(Fused finger bones of the hand)
- Synostosis of carpal bones
- Fusion of wrist bones
1%-4% of people have these symptoms
- Carpal synostosis
- Distal symphalangism of hands(Fused outermost bones of hand)
- Proximal symphalangism of hands(Fused innermost hinge joints)
- Short 1st metacarpal(Shortened 1st long bone of hand)
Diagnosis[edit | edit source]
Clinical examination of the thumb anomalies and distal phalangeal hypoplasia, and absence of nails sometimes with associated distal symphalangism. Radiological examination of the hands and pattern profile analysis.[2].
References[edit | edit source]
Treatment[edit | edit source]
- There is no specific management or treatment that is applicable to all forms of brachydactyly.
- Plastic surgery is only indicated if the brachydactyly affects hand function or for cosmetic reasons, but is typically not needed.
- Physical therapy and ergotherapy may ameliorate hand function.[3].
Prognosis[edit | edit source]
- Prognosis for the brachydactylies is strongly dependent on the nature of the brachydactyly, and may vary from excellent to severely influencing hand function.
- If brachydactyly forms part of a syndromic entity, prognosis often depends on the nature of the associated anomalies.
References[edit | edit source]
- ↑ Temtamy, S. A., & Aglan, M. S. (2008). Brachydactyly. Orphanet journal of rare diseases, 3, 15. https://doi.org/10.1186/1750-1172-3-15
- ↑ Temtamy, S. A., & Aglan, M. S. (2008). Brachydactyly. Orphanet journal of rare diseases, 3, 15. https://doi.org/10.1186/1750-1172-3-15
- ↑ Temtamy, S. A., & Aglan, M. S. (2008). Brachydactyly. Orphanet journal of rare diseases, 3, 15. https://doi.org/10.1186/1750-1172-3-15
NIH genetic and rare disease info[edit source]
Brachydactyly type B is a rare disease.
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