Anatomical variations of the structures in the neck are of clinically significance and success of various surgical procedures and circumventing potential possibilities of iatrogenic lesions in the region entirely depends on precise knowledge [1,2]. The thyroid gland consists of two lateral lobes joined by a midline isthmus.

Isthmus lies at the level of second to fourth tracheal rings and is enveloped by infrahyoid muscles. Occasionally an extrapyramidal lobe is also present attached to the isthmus [3]. The upward-pointing apex of this pyramidal lobe has a fibromuscular band extending from here to hyoid bone [4]. It develops from remains of the thyroglossal duct, which seldom gets muscle fibers and eventually form this band.

Embryologically, the thyroid gland is the foremost to start developing amongst endocrine glands. In addition, it is frequently observed to be associated with congenital anomalies of varying degrees. They range from common ones as variations in lobes pyramidal lobe and presence of thyroglossal duct cyst to sporadic ones as partial or complete agenesis of lateral lobes, isthmus, or even whole gland [5,6].

The congenital anomalies during the development of the gland alter the usual morphology. As a result, it ends up leading to several clinical conditions and various thyroid disorders [7]. Literature reported isthmus agenesis to vary from a range of 5-10% and even confined to 8-10% [8,5]. It is challenging and indefinite to find the incidence of isthmus agenesis for the reason that the analysis predominantly based on populations presented with some or other thyroid diseases [8].

During routine dissection in the Department of Anatomy at All India Institute of Medical Sciences Jodhpur, a 52-year-old male cadaver exhibited agenesis of the isthmus of the thyroid gland leading to its absence. Intact skin of anterior cervical region with no visible scar ruled out any possibility of surgical procedure carried out in the past.

The thyroid gland was found with two separate lateral lobes, with complete agenesis of the isthmus. The pyramidal lobe on the left side was large and prominent whereas on the right side lobe had a

[9,10]. Agenesis of the isthmus is a rare developmental entity. It also showed gender disparity with the predominance of the condition in males as compared to females [10]. In the present study, the agenesis is reported in a male cadaver.

According to Gruber (cited by Testut), the incidence of agenesis is about 5% [6]. Allan and authors in there study found it be in the range of 2-4% but according to Marshall, it is higher i.e. up to 15% [5,11]. In an Indian study, the incidence was moreover even found a little higher than this i.e. 16.66% [12].

Levator glandulae thyroidea is found to be 30% in a study on Indian diaspora [12]. Incidence of it was slightly higher up to 43.33% in the Bangladesh population [13]. According to Ranade et al the incidence reported was even more i.e. 49.5% [14]. In classical literature levator glandulae, thyroidea is seen to extend from the pyramidal lobe or moreover mostly from the left lobe or left side of the isthmus to be attached to the hyoid bone cranially [15]. In the present case, there is an unusual presentation of the levator glandulae thyroidae. It extended as a slip from the tip of both the lobes and eventually join to form a single band and attached to the body of the hyoid bone. The occurrence of isthmus agenesis was reported ranging from 3 to 10% [14,16]. Lack of data with the precise number was not found and it might be because generally occurrence is in non-symptomatic population and reported data are based mostly on cadaveric studies. In clinical setting agenesis of the isthmus is often seen to be associated with conditions as nodular goiter, inflammation, or primary carcinoma [8]. It is observed that the etiology of agenesis is moreover indistinct. Innategenetic factors and defects in development inintra uterine life has a pivotal role. Genetic mutations accountable for normal development can be another reason for isthmus agenesis. Principally it involves TITF1-2 genes and chromosome 22 [17,18].

In the early gestation phase on the 24th day, the thyroid starts developing. The lateral thyroid develops from neural crest cells, while the isthmus arises from the primitive pharynx. The development of thyroglossal duct arises from the endodermal layer in the pharyngeal floor at the level of second and third pharyngeal pouches. It grows downwards and anterior to the trachea to split into two lateral lobes [5,8,14,16]. It was also found that defective or imperfect fusion of the thyroglossal duct in the midline basically is responsible for ending into the