Howard Fischer
Uppsala, Sweden

“…he had been born and had grown up with a cartilaginous tail in the shape of a
corkscrew with a small tuft of hair on the tip.”
— Gabriel García Márquez, One Hundred Years of Solitude¹

The chance of a child being born with a tail-like lumbosacral appendage is small. About sixty cases have been recorded in the medical literature.² Boys are twice as likely to have a tail.^3,4,5 It may be less than one centimeter long at birth, or more than eight centimeters.⁶ If not removed, the tail continues to grow with the child.⁷ The longest documented tail in an adult man was thirty-three centimeters.⁸ Human tails have been described as “resembling a finger, sausage, penis, pigtail, or elephant’s trunk.”⁹ There is only one report of familial occurrence, with one person born with a tail in each of three generations.¹⁰

Like our vertebrate ancestors, human embryos have a tail, which appears at about five weeks of gestation.¹¹ It contains ten to twelve vertebrae, is most prominent at thirty-five days, and is gone by eight or nine weeks of gestation.^12,13 This timing is not absolute, since six fetuses had lumbosacral appendages seen on ultrasound examination, but one appendage was gone by fifteen weeks, and the others by twenty-two or twenty-three weeks of gestation.¹⁴

Our coccyx, or tailbone, is the remnant of this lost tail, and is composed of three to five separate or fused vertebrae. Its name comes from the ancient Greek kokkyx, meaning cuckoo, since the end of the coccyx is said to look like a cuckoo’s beak when seen from the side.¹⁵ There is a difference between “true human tails” and “pseudotails.” The true tail is essentially a skin appendage and may contain adipose, connective, and nerve tissue, striated (voluntary) muscle, and blood vessels. It does not contain bone, cartilage, or spinal cord. Pseudotails are considered “anomalous prolongations of sacrococcygeal vertebrae.” They may be associated with lipomas (fatty tumors), teratomas (tumors containing teeth, hair, bone, and muscle), or gliomas (composed of nerve tissue).

Small case series¹⁶ may not demonstrate anomalies associated with true human tails, but larger series show a fifty percent incidence of spina bifida occulta¹⁷—a vertebral defect of no clinical significance—but sometimes also serious spinal anomalies. Pseudotails, however, are very often associated with anomalies of the spinal cord and meninges.¹⁸

The birth of an infant with a tail is, understandably, a shocking and disturbing event for parents. It is seen as more than a curiosity or a cosmetic problem.^19,20 Much depends on the parents’ literacy and beliefs. They may see the tail’s presence as a curse and a cause for shame, or, on the contrary, as an auspicious gift. Giri and Charav describe a patient who first came to medical attention at the age of seventeen. This young man had an eighteen-centimeter tail, which was making it hard for him to sit. His parents believed that the one- or two-centimeter tail he had at birth was a gift from God.²¹

Some individuals may have a small hole at the upper end of the gluteal cleft. This hole is usually connected to a sinus track (a sort of tunnel) that extends to a variable depth. In the nineteenth and early twentieth century, people believed that this pilonidal sinus was left over from a resorbed tail.²² There are still those who ask if the pilonidal sinus, with an incidence of one or two in 1000, is a congenital condition.²³ When this sinus track gets infected it forms a pilonidal cyst. Such cysts are seen often in taxi drivers and were present in 80,000 American soldiers (mostly jeep drivers) in World War Two, indicating that this is an acquired condition. The initiating factor is probably a hair curving back and penetrating the skin, that is, an ingrown hair. Contributing factors are obesity, prolonged sitting, and hormonal changes at puberty.²⁴

Regarding human tails, physicians and parents need to know is that since “skin and nervous system are intimately linked by their similar ectodermal origin, a dorsal appendage may be regarded as a cutaneous marker of [an]…underlying spinal dysraphism [a defect in the bony spine and the spinal cord].”²⁵

References

1. Gabriel García Márquez. One Hundred Years of Solitude. New York: Avon Books, 1971.
2. Md Islam, Suman Adhikari, Mohammad Alam, et al. “Experience with human tail and its outcome,” Afr J Paediatric Surg, 18(1), 2021.
3. Cezmi Turk, Niyazi Kara, Ali Bancali. “The human tail: A simple skin appendage or cutaneous stigma of an anomaly?” Turk Neurosurg,26(1), 2016.
4. Mahesh Pillai, Smitha Nair. “A true human tail in a neonate.” Sultan Qaboos Univ Med J, 17(1), 2017.
5. Biswanath Mukhopadhyay, Ram Shukla, Madhumita Mukhopanhyay, et al. “Spectrum of human tails: A report of six cases: J Ind Assoc Paediatr Surg, 17(1), 2012.
6. Mukhopadhyay. “Spectrum.”
7. Pramod Giri and Vaibhav Chavan.” Human tail: a benign condition hidden out of social stigma and shame in young adult,” Asian J Neurosurg, 14(1), 2019.
8. NA. “Longest human tail,” Guinness World Records, ND.
9. Islam. “Experience.”
10. Pillai. “Neonate.”
11. NA. Human vestigiality. Wikipedia. ND.
12. Mukhopadhyay. “Spectrum.”
13. Human vestigiality. Wikipedia.
14. Zeev Efrat, Tamar Perri, Israel Meizner, et al. “Early sonographic detection of a ‘human tail’: A case report,” Ultrasound in Obstetrics and Gynecology, 18, 2001.
15. NA. Coccyx. Wikipedia. ND.
16. Turk. “Stigma.”
17. Giri. “Shame.”
18. Mukhopadhyay. “Spectrum.”
19. Giri. “Shame.”
20. Mukhopadhyay. “Spectrum.”
21. Giri. “Shame.”
22. Alex Koyfman. “Pilonidal cyst and sinus: Background, pathophysiology, epidemiology,” Emedicine, 2019. emedicine.medscape.com.
23. Efrat. “Sonographic.”
24. XiXi Luo. “Pilonidal sinus: Causes, symptoms, and treatment,” Healthline.com, 2018.
25. Abhijit Dutta, Sudip Ghosh, Asoh Mandal. “A tale of two tails: Not just skin deep,” Indian J Dermatol, 60(4), 2015.