|Year : 2015 | Volume
| Issue : 1 | Page : 92-94
Human tail and limb defects: A short tale of a long tail
Balike Krishna Praveen1, Kallekkattu Dipu2
1 Department of Pediatrics, Father Muller Medical College, Mangalore, Karnataka, India
2 Department of Pediatrics, Jubilee Mission Medical College and Research Institute, Thrissur, Kerala, India
|Date of Web Publication||8-Dec-2014|
Balike Krishna Praveen
Department of Pediatrics, Father Muller Medical College, Mangalore - 575 002, Karnataka
Source of Support: None, Conflict of Interest: None
A human tail is a congenital, caudal, cutaneous appendage, which usually arises from the tip of the coccyx or it is a finger-like protrusion at the lumbosacral region. It usually indicates the presence of an underlying occult spinal dysraphism. Herein, the authors report a rare case of a human tail, along with multiple anomalies of the limbs in a newborn. The embryological basis for the association is also highlighted.
Keywords: Embryogenesis, human tail, limb bud, limb defects, syndactyly, tail bud
|How to cite this article:|
Praveen BK, Dipu K. Human tail and limb defects: A short tale of a long tail. Muller J Med Sci Res 2015;6:92-4
| Introduction|| |
A birth defect demonstrates pleiotropy when a single underlying causative agent, such as a mutant gene or a teratogen, results in abnormalities of more than one organ system in different parts of the embryo or in multiple structures that arise at different times during intrauterine life. Pleiotropic birth defects manifest in two different ways depending on the mechanism by which the causative agent produces its effect. When the causative agent produces multiple abnormalities in parallel, the collection of abnormalities is referred to as a syndrome. If however, a mutant gene or teratogen affects only a single organ system at one point in time and it is the perturbation of that organ system that causes the rest of the constellation of pleiotropic defects to occur as secondary effects, the malformation is referred to as a sequence. 
A skin tag or acrochordon is a soft, fleshy, polypoid, and pedunculated lesion. Childhood acrochordons are solitary, often congenital, and most commonly occur over the trunk, lumbosacral region, groin, and perineal areas. Histopathological examination reveals a polypoid tumor with a dermis that lacks appendages and is composed of loose connective tissue, fat and telangiectatic vessels and an epidermis that may range from being atropic to acanthotic. 
The presence of cutaneous, midline congenital lesions in the lumbosacral region, such as, vascular nevus, tufts of hair, dermal sinuses, subcutaneous lipomas, deviated gluteal furrows, and a human tail may indicate the presence of an underlying occult spinal dysraphism (OSD).  The presence of a human tail is very uncommon. The authors herein report a rare case of a human tail along with multiple limb defects in a newborn.
| Case Report|| |
A one-day-old female newborn, weighing 2720 g, born vaginally to a primigravida mother, was referred for a 'tail-like' structure noticed at the lumbosacral area and an abnormal growth arising from the left leg. The baby was born after an uneventful pregnancy to nonconsanguineous parents. There was no history of any illness, exposure to radiation or intake of teratogenic drugs during the pregnancy. The mother had undergone only one antenatal ultrasound at the tenth week of gestation, which was documented as normal. On physical examination of the newborn, a 9 cm long, soft, nontender, non-pulsatile, nonfluctuant, normal skin covered appendage was present, attached to the tip of the coccyx, appearing like a human tail. Power, reflexes, and sensations of the lower limbs were normal. The baby did not have any bowel and bladder dysfunction. A soft, nontender, finger-like tissue mass, measuring 6.3 cm in length, was seen protruding from the medial aspect of the left leg. The infant had a congenital talipes equinovarus (CTEV) deformity of the left foot and syndactyly involving the middle three fingers and toes, bilaterally [Figure 1] and [Figure 2]. A systemic examination of the newborn did not reveal any abnormality.
|Figure 1: Human tail with soft tissue mass attached to the left leg, syndactyly of toes, and CTEV of left foot|
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Her electrocardiogram (EKG), two-dimensional echocardiogram (2D-ECHO), and ultrasound (US) abdomen were normal. Ultrasound examination of the lumbosacral region revealed an extension of the appendage into the subcutaneous soft tissue, with no intraspinal involvement. Magnetic resonance imaging (MRI) of the spine could not be done due to financial constraints. An x-ray of the left leg did not reveal the presence of bone in the soft tissue mass. Surgical excision of the 'tail' was performed on the fifth day of life. Histopathological examination of the appendage revealed the presence of adipose tissue, connective tissue, blood vessels, and nerves, and absence of bone, notochord, and spinal structures. Surgical release of syndactyly and excision of the soft tissue mass attached to the leg was done at three months of age. Surgical correction of the CTEV was done at the age of six months and subsequently the child was put on corrective footwear.
On follow-up at one-and-a-half years of age, the child had attained all age appropriate milestones and was developmentally normal, with no neurological deficits.
| Discussion|| |
A human tail is considered as one of the markers of an underlying Occult Spinal Dysraphism (OSD). Human tails may be located anywhere, from the cervical region to 2.5 cm to the anus, in the midline. , It occurs twice as often in males as compared to females. Human tails are classified as true and pseudo tails. The true tail contains adipose tissue, connective tissue, muscles, vessels, and nerves, and is capable of spontaneous reflex motion, whereas, the pseudo tail comprises of bone, cartilage, vertebra, and the remnants of a notochord.  A true tail is considered as benign, which can be removed surgically without any residual effects.  Association of a human tail with spina bifida, lumbar meningomyelocele, lipomyelocele, lipoma, tethered cord syndrome, teratoma, cleft palate, congenital heart defects, anal and vaginal atresia, and horse-shoe kidney have been reported. , A complete neurological evaluation followed by imaging of the spine is required in all the cases, as around 50% of cases of human tail are associated with OSD. 
The embryogenesis of the human tail begins at the fourth week of gestation. A compact mass called the 'tail bud' is formed at the caudal end of the embryo following formation of somites.  It is composed of paired somites, mesenchyme, and extensions of the neural tube, notochord, and gut.  During the fifth and sixth weeks, it contains 10-12 vertebrae. During the seventh and eighth weeks, the vertebrate portion retracts into the soft tissue. The nonvertebrate part is phagocytosed by macrophages and the debris-laden macrophages migrate from the tail to the body causing the disappearance of the tail by eight weeks. 
The limb buds develop as outpocketings from the ventrolateral body wall by the end of the fourth week. Initially, they consist of a mesenchymal core covered by the ectoderm. The ectoderm at the distal border of the limb thickens to form the apical ectodermal ridge (AER). Cell death in the AER separates this ridge into fingers and toes.  Thus, abnormal embryogenesis involving cell death may be considered as the possible mechanism for the presence of a human tail and limb defects in our patient.
This case is reported in view of the unique association of the 'human tail' with limb defects, which highlights a common embryological pathogenesis. Long-term follow-up to detect the occurrence of tethered cord syndrome is needed in this child.
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[Figure 1], [Figure 2]