Bohn's Nodules

What Are Bohn's Nodules?

Lesions that are keratin-filled cysts in the newborn's mouth are called Bohn's nodules. These nodules are commonly found in the infant's mouth over the palate or the buccal or lingual surfaces of the alveolar ridges or occasionally along the hard and soft palate junction. They are derivatives of palatal salivary glands and are numerous and scattered along with these locations in the child's oral cavity. The appearance of these developmental cysts can cause anxiety and concern to anxious parents.

They can be simply explained as mucous gland cysts that do not exceed 3 mm in size (typically always less than 3 mm) and have a firm, nodular consistency with a grayish-white appearance. The occurrence of these cystic lesions varies between 0 to 36-month-old infants, with a 20.8% prevalence in this age group.

What Are Epstein Pearls and Gingival Cysts?

Heinrich Bohn, a German physician, described the appearance and occurrence of the newborn inclusion cyst and hence the name Bohn's nodules. However, as per a larger classification according to Alfred Fromm, who classified gingival cysts based on origin (1967) – the three main types of gingival cysts that occur in the newborn are:

1. Epstein pearls.
2. Bohn's nodules.
3. Dental lamina cysts.

Often dental surgeons confuse these appearances or Bohn's nodules on the infant's palate to be large Epstein pearls. Still, the Epstein pearls are keratin-filled nodules that occur only along the mid palatine raphe. Hence, the location of these cysts helps differentiate Bohn's nodules from Epstein pearls. Also, the origin of the Epstein pearls is from the entrapped remnants along the line of fusion and are epithelial. One more point of differentiation is the Epstein pearls are white and may be quite large compared to the small nodules that are Bohn's nodules. Epstein pearls also have the highest prevalence in relation to newborn cystic manifestations.

Similarly, in adults, the gingival cysts are odontogenic developmental cysts just like Bohn's nodules and Epstein pearls (but are not found in infants, they are seen only in adults). These gingival cysts are derived from the cell rests of the dental lamina and found on the buccal and labial surfaces of the gingiva. Also, they develop quite late in adulthood, almost around the sixth decade, and are a comparatively rare condition in adults given the frequent incidence of dental-originated cysts.

What Is the Pathogenesis of Bohn's Nodules?

In the first trimester of pregnancy, that is, after the initial eight weeks of intrauterine fetal life, the palate starts to develop by the fusion of the lateral palatine processes that are in turn generated by the maxillary processes. These lateral palatine processes are in the lateral aspect of the oral cavity and grow in a downward direction towards the midline. From 8 weeks to 12 weeks of intrauterine fetal growth, the palate is usually completely formed by fusing these palatine processes with the nasal septum and premaxillary processes. Hence the entrapment of mucous membranes manifests as tiny superficial yet firm bumps in the palate.

The formation of Bohn's nodules and Epstein pearls is attributed to the theory that epithelium gets trapped during the palate formation, forming cystic content during development. Alternatively, other theories suggest the palate formation is alongside the epithelial remnants from the minor salivary glands of the palate that may result in these inclusion cysts to form simultaneously with the palatal development in the newborn infant.

What Are the Differential Diagnosis of Bohn's Nodules?

Parents are often anxious to notice these gray to whitish nodules in their infant's mouth and consult a pediatrician who may usually diagnose these cystic lesions as neonatal teeth or an oro-fungal infection like candidiasis. Parents present the chief complaint of anxiety to the physician or pediatrician as they fear injury to the baby's oral tissues while feeding, or they fear that the swallowing moment is improper or affected in their infant.

A consultation with the dental surgeon helps the parents rule out other lesions that resemble Bohn's nodules. After visual examination, the dentist will consider the following conditions for a differential diagnosis:

1. Epstein Pearls - As mentioned earlier, they are whitish nodules found only on the mid palatine raphe and may vary from small to large diameter in size instead of Bohn's nodules which are less than 3 mm.
2. Dental Lamina Cysts - They are fluctuant, solitary lesions that are transparent in appearance. They are found on the alveolar mucosa crest.
3. Natal and Neonatal Teeth – It is rare to find immediately in a newborn child. Even if they are present, they are located in the lower incisor region and associated with major developmental anomalies of the infant.
4. Ranula or Extravasation Cysts - Are found only near the frenulum of the tongue (lingual frenum) and are translucent firm nodules or papules.
5. Congenital Epulis - These are pedunculated and soft lesions typically found on the gingival margins.
6. Alveolar Lymphangioma - Bluish solitary or multiple scattered lesions found commonly on alveolar ridges and not seen on the palate.

How Are Bohn's Nodules Managed?

A dental surgeon will reassure the parents that this condition is harmless and self-healing. The lesions disappear on their own, usually within three months of age of the infant by the rupture of the cystic keratin contents into the oral cavity. However, the surgeon can only approach this conclusion after differential diagnosis by visual or clinical examination of the infant. Almost all the Bohn's nodules do not present with swelling or pain and should be considered for excision only when they do not disappear rarely or tend to enlarge (that can interfere with the mother's feeding).

Conclusion:

Hence to conclude, Bohn's nodules are like any other oral lesions in neonates that are harmless and benign. Consulting the dental surgeon and watchfulness of the lesion, whether it enlarges or spontaneously ruptures and disappears over time, is the only preventive modality for these inclusion cysts in the newborn.

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