Unilateral submandibular gland aplasia: a rare phenomenon.
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Aplasia (agenesis) of a salivary gland is a very uncommon condition. (1-4) The salivary glands arise as a result of the proliferation and ingrowth of the oral epithelium as a solid core of cells; these cells form the underlying mesenchymal tissues near the fourth to eighth week of fetal development. As development progresses, these core cells undergo extensive branching, they enlarge, and they acquire lumina. The proximal portion of the original primordium becomes the main duct of the salivary glands, and the terminal ducts dilate to form the secretory acini. The surrounding mesenchyme divides the glands into lobules and envelops the gland to form a capsule. (5) Salivary gland aplasia may occur secondary to a disturbance of the first and second brachial arches during early fetal development. (1)
Congenital unilateral absence of the submandibular gland is an isolated phenomenon that is not associated with other facial anomalies. (6) While patients with salivary gland aplasia often present with xerostomia, dysphagia, and/or dental caries, unilateral submandibular aplasia is often asymptomatic and is usually discovered incidentally on imaging. (6) In such cases, intraoral examination will reveal that the aplastic submandibular papilla are rudimentary in comparison with the normal appearance on the opposite side, but the opening of Wharton's duct may still be found. (6) Sialography may be attempted by cannulating the Wharton duct to confirm the agenesis of the submandibular gland. Likewise, the submandibular gland may not be found by bimanual palpation, and saliva may not be obtained from the duct orifice by pressing the submandibular area on the side of the aplasia. (4)
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The characteristic imaging feature of submandibular gland aplasia, of course, is the absence of the submandibular gland, which is often replaced by fatty tissue. Moreover, the submandibular gland on the opposite side may become hypertrophied as a means of compensating for the aplastic submandibular gland? This hypertrophic change may mimic a mass. (7) Sialography may demonstrate only a portion of the Wharton duct as a club-shaped dilation of its proximal end; it may fail to show the rest of the submandibular gland. (6) This incomplete image may be attributable to unilateral agenesis of the secretory acini of the terminal duct that was formed from the submandibular gland primordium during early fetal development. The absence of the gland may also be demonstrated by sonographic evaluation and nuclear medicine examination. (4,7)
We evaluated 2 patients with prominent posterior cervical lymphadenopathy and symptoms consistent with viral illness--a 35-year-old woman and a 7-year-old boy. On examination and imaging, both patients were noted to have unilateral aplasia of the subman dibular gland and hypertrophy of the opposite gland, which at first was believed to represent a mass or lymphadenopathy (figures 1 and 2).
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Otolaryngologists and radiologists should be familiar with the possibility of unilateral submandibular gland aplasia with compensatory hypertrophy of the opposite gland mimicking abnormal enlargement or lymphadenopathy. Note that compensation can also occur following unilateral submandibular gland resection (figure 3).
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(2.) Abdel-Dayem HM. Congenital absence of submaxillary gland detected on 99mTc-pertechnetate thyroid imaging. Clin Nucl Med 1978;3(11):422.
(3.) Garcia-Consuegra L, Gutierrez LJ, Castro JM, Granado JF. Congenital unilateral absence of the submandibular gland. J Oral Maxillofac Surg 1999;57(3):344-6.
(4.) Yilmaz MD, Yucel A, Derekroy S, Altuntas A. Unilateral aplasia of the submandibular gland. Eur Arch Otorhinolaryngol 2002;259(10):544-6.
(5.) Johns ME. The salivary glands: Anatomy and embryology. Otolaryngol Clin North Am 1977;10(2):261-71.
(6.) Roh JL. Unilateral submandibular gland aplasia: An isolated phenomenon of early fetal development. Otolaryngol Head Neck Surg 2006;135(2):332-4.
(7.) Srinivasan A, Moyer JS, Mukherji SK. Unilateral submandibular gland aplasia associated with ipsilateral sublingual gland hypertrophy. AJNR Am J Neuroradiol 2006;27(10):2214-16.
Neel Gupta, MD; Enrique Palacios, MD, FACR; Shannon Barry, MS
From the Department of Radiology, Tulane University Hospital and Clinic, New Orleans.