brachydactyly type B2

Brachydactyly type B2 (BDB2) is a rare, genetic congenital limb malformation disorder characterized by hypoplasia/aplasia of distal and/or middle phalanges in fingers and toes II-V (frequently severe in fingers/toes IV-V, milder in fingers/toes II-III) in association with proximal, and occasionally distal, symphalangism, fusion of carpal/tarsal bones, and partial cutaneous syndactyly [1][2][3].

This condition is a subtype of brachydactyly type B, which is characterized by the incomplete development or absence of the outermost bones of the fingers and toes (distal phalanges) and nails [4]. Brachydactyly type B2 specifically involves hypoplasia/aplasia of distal phalanges in combination with distal symphalangism, fusion of carpal/tarsal bones, and partial cutaneous syndactyly [5][6].

Brachydactyly type B2 is inherited in an autosomal dominant pattern, meaning that a single copy of the mutated gene is enough to cause the condition [7]. It is essential to note that brachydactyly can occur either as an isolated malformation or as part of a complex malformation syndrome [8].

In summary, Brachydactyly type B2 is a rare genetic disorder characterized by the incomplete development or absence of distal phalanges in fingers and toes, associated with symphalangism, fusion of carpal/tarsal bones, and partial cutaneous syndactyly.

Brachydactyly type B2 (BDB2) is a rare genetic congenital limb malformation disorder characterized by several distinct signs and symptoms.

Hypoplasia/Aplasia of Distal Phalanges The most common sign of BDB2 is the hypoplasia or aplasia of distal phalanges in fingers and toes II-V. This means that the outermost bones of these digits are either underdeveloped (hypoplastic) or completely absent (aplastic).

Distal Symphalangism In addition to the above, BDB2 is also associated with distal symphalangism, which refers to the fusion of the distal phalanges. This can result in a webbed appearance between the fingers and toes.

Fusion of Carpal/Tarsal Bones Another characteristic feature of BDB2 is the fusion of carpal bones in the wrist and tarsal bones in the ankle. This can lead to restricted mobility and flexibility in these joints.

Partial Cutaneous Syndactyly In some cases, individuals with BDB2 may also experience partial cutaneous syndactyly, which refers to the webbing or fusion of skin between the fingers and toes.

These signs and symptoms are typically present at birth, although they can become more noticeable as the individual grows and develops. A diagnosis of BDB2 is usually made through a combination of clinical evaluation, medical history, and imaging studies such as X-rays.

References: * [11] Brachydactyly type B2 is a rare, genetic congenital limb malformation disorder characterized by hypoplasia/aplasia of distal and/or middle phalanges in fingers and toes II-V (frequently severe in fingers/toes IV-V, milder in fingers/toes II-III) in association with proximal, and occasionally distal, symphalangism, fusion of carpal/tarsal bones and partial cutaneous syndactyly. * [13] Brachydactyly type B2 (BDB2) is a subtype of brachydactyly characterized by hypoplasia/aplasia of distal phalanges in combination with distal symphalangism, fusion of carpal/tarsal bones, and partial cutaneous syndactyly.

Brachydactyly type B2 is a rare genetic congenital limb malformation disorder, and diagnosing it requires

Brachydactyly type B2 (BDB2) has a differential diagnosis that includes several conditions with similar characteristics. Some of the key conditions to consider in the differential diagnosis of BDB2 are:

• Pseudohypoparathyroidism (PHP): This is a rare genetic disorder characterized by short stature, round face, and short fingers and toes. PHP can be confused with BDB2 due to its similar skeletal features.
• Pseudopseudohypoparathyroidism (PPHP): This condition is a milder form of PHP and also presents with short fingers and toes. It can be challenging to distinguish from BDB2, especially in mild cases.
• Acrodysostosis: This is a rare genetic disorder characterized by short stature, short fingers and toes, and other skeletal abnormalities. Acrodysostosis can be confused with BDB2 due to its similar skeletal features.

These conditions are all part of the differential diagnosis for BDB2 because they share some similarities in their clinical presentation. However, each condition has distinct characteristics that can help differentiate it from BDB2.

• Pseudohypoparathyroidism (PHP): PHP is characterized by short stature, round face, and short fingers and toes [5]. It is caused by mutations in the GNAS gene [5].
• Pseudopseudohypoparathyroidism (PPHP): PPH is a milder form of PHP and presents with short fingers and toes, but without the characteristic round face [5]. It is also caused by mutations in the GNAS gene [5].
• Acrodysostosis: Acrodysostosis is characterized by short stature, short fingers and toes, and other skeletal abnormalities [5]. It is caused by mutations in the IHH gene [5].

It's worth noting that a definitive diagnosis of BDB2 can only be made through genetic testing and clinical evaluation. A thorough medical history, physical examination, and imaging studies (such as X-rays or CT scans) are essential for distinguishing BDB2 from other conditions with similar features.

References: [5] - OMIM: Online Mendelian Inheritance in Man.