There isn't one single "rare thumb." Rarity depends on the specific condition affecting the thumb. Several rare thumb conditions are documented:
Rare Thumb Conditions:
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Brachydactyly Type D: This genetic condition results in a relatively short thumb, also known as a short thumb, stub thumb, or clubbed thumb. Source: Wikipedia - Brachydactyly type D
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Clasped Thumb: A congenital clasped thumb is a rare condition characterized by the absence of certain extensor muscles in the thumb, resulting in a bent or clasped thumb position. Source: NCBI - A rare case of neglected clasped thumb
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Snapping Thumb (Stenosing Tenosynovitis of the Extensor Pollicis Longus): While tenosynovitis isn't inherently rare, its occurrence in the extensor pollicis longus tendon of the thumb, without rheumatoid arthritis, is relatively uncommon. Source: NCBI - Snapping thumb
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Tumors: Rare tumors, such as plexiform schwannomas, can affect the thumb. Source: NCBI - A Rare Presentation of Plexiform Schwannoma
Additionally, while hitchhiker's thumb (the ability to hyperextend the distal interphalangeal joint of the thumb beyond 90 degrees) is a common trait, it can be associated with rare genetic diseases in some cases. Source: Cleveland Clinic - Hitchhiker's Thumb
The rarity of any specific thumb condition depends on the prevalence in the population, making a definitive answer to "which thumb is rare" impossible without specifying the condition.
