**Core Concept**
Arachnodactyly, also known as spider fingers, is a clinical feature characterized by long, slender fingers with a characteristic curvature, resembling the legs of a spider. This condition is often associated with genetic disorders that affect connective tissue.

**Why the Correct Answer is Right**
Arachnodactyly is a hallmark feature of Marfan syndrome, a genetic disorder caused by mutations in the FBN1 gene. This gene encodes for fibrillin-1, a protein essential for the formation of elastic fibers in connective tissue. In Marfan syndrome, the defective fibrillin-1 protein disrupts the normal structure and function of connective tissue, leading to various clinical manifestations, including arachnodactyly. The long fingers and toes in Marfan syndrome are a result of the increased length and decreased joint mobility of the fingers and toes.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Marfanoid habitus, characterized by tall stature and long limbs, is a distinct feature from arachnodactyly. While these conditions may coexist, they are not synonymous.

**Option B:** This option is incorrect because acromegaly, a disorder caused by excess growth hormone, can lead to enlargement of the hands and feet, but not necessarily the characteristic curvature and lengthening of the fingers seen in Marfan syndrome.

**Option C:** This option is incorrect because Ehlers-Danlos syndrome, a group of genetic disorders affecting connective tissue, can cause skin hyperextensibility and joint hypermobility, but is not typically associated with arachnodactyly.

**Option D:** This option is incorrect because osteogenesis imperfecta, a disorder affecting bone formation, can cause bone fragility and deformity, but is not associated with the characteristic finger curvature and lengthening of arachnodactyly.

**Clinical Pearl / High-Yield Fact**
Marfan syndrome is a classic example of a genetic disorder affecting connective tissue, and arachnodactyly is a key clinical feature that should prompt further evaluation for this condition.

**Correct Answer:** C. Ehlers-Danlos syndrome is incorrect; the correct answer for Marfan syndrome is not listed.