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Arachnodactyly refers to abnormally long and slender fingers and toes, resembling a spider’s legs. It is a clinical sign often associated with genetic connective tissue disorders, especially Marfan syndrome and congenital contractural arachnodactyly (CCA).
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Clinical Assessment Criteria:
| Sign | Description |
|---|---|
| Thumb Sign (Steinberg sign) | When the thumb is bent across the palm and covered by the fingers, the tip protrudes beyond the ulnar border of the hand |
| Wrist Sign (Walker-Murdoch sign) | When the thumb and fifth finger overlap around the contralateral wrist, indicating long digits |
| Syndrome | Features |
|---|---|
| Marfan syndrome | Tall stature, aortic root dilation, lens dislocation, scoliosis |
| Congenital contractural arachnodactyly (Beals syndrome) | Crumpled ears, joint contractures, scoliosis, mutation in FBN2 |
| Homocystinuria | Similar to Marfan (tall, thin), but with mental retardation, thromboembolic events, and downward lens dislocation |
| Ehlers-Danlos syndrome | Hyperextensible skin, joint hypermobility, vascular fragility |
| Loeys–Dietz syndrome | Aortic aneurysms, bifid uvula, hypertelorism, skeletal features similar to Marfan |
| Stickler syndrome | Midface hypoplasia, retinal detachment, joint hypermobility, hearing loss |
| Modality | Findings |
|---|---|
| Hand X-ray | - Long, slender metacarpals and phalanges |
| Condition | Distinguishing Features |
|---|---|
| Marfan syndrome | Positive wrist/thumb signs, aortic root disease, ectopia lentis |
| Beals syndrome | Joint contractures, crumpled ears, no eye or heart involvement |
| Homocystinuria | Developmental delay, thromboembolism, downward lens dislocation |
| Klinefelter syndrome | Tall stature, hypogonadism, XXY karyotype |
| Suspected Condition | Gene |
|---|---|
| Marfan syndrome | FBN1 |
| Beals syndrome (CCA) | FBN2 |
| Loeys–Dietz syndrome | TGFBR1/2, SMAD3 |
| Homocystinuria | CBS (cystathionine beta-synthase deficiency) |
Arachnodactyly itself is not treated directly but: