Syndromes recognised at the chair

Correct answer: D. Autosomal dominant with variable expressivity

• A. X-linked recessive inheritance would produce a male-predominant pattern with transmission through carrier mothers, not from an affected father to a child.
• B. Mitochondrial inheritance passes exclusively through the mother and does not fit.
• C. Autosomal recessive inheritance would require two carrier parents and would not show the father-to-child transmission described.
• D. Correct. Cherubism is autosomal dominant with variable expressivity and reduced penetrance in females, caused by mutations in the SH3BP2 gene. It presents between 2 and 5 years with painless bilateral expansion of the jaws, radiographically multilocular radiolucencies, and characteristically it regresses spontaneously after puberty.

Correct answer: B. Hereditary and developmental

• A. Reactive lesions such as the central giant cell granuloma respond to a local stimulus. Cherubism is genetically determined and bilateral from the outset, which reactive lesions are not.
• B. Correct. Cherubism is a hereditary developmental condition, driven by a germline mutation and expressed during jaw development. Its self-limiting course, with regression after puberty, is characteristic of a developmental rather than a neoplastic process.
• C. There is no infectious agent involved.
• D. It is not a neoplasm. There is no autonomous clonal proliferation, and the lesions regress spontaneously.

Correct answer: C. Trisomy 21

• A. Trisomy 13, Patau syndrome, is rarer still and likewise has very high early mortality.
• B. Trisomy 18, Edwards syndrome, is far less common and carries a very poor prognosis, with most affected infants dying in the first year.
• C. Correct. Trisomy 21, Down syndrome, is the most common autosomal trisomy, occurring in roughly 1 in 700 live births with incidence rising with maternal age. Dental features include delayed and irregular eruption, hypodontia, microdontia, macroglossia with fissuring, a Class III tendency and markedly increased periodontal disease.
• D. Trisomy 16 is the most frequent trisomy at conception but is uniformly lethal in the first trimester, so it is not seen at birth.

Correct answer: D. Treacher Collins syndrome

• A. Crouzon syndrome features craniosynostosis with midface hypoplasia, proptosis from shallow orbits and a Class III relationship, but the ears are typically normal.
• B. Pierre Robin sequence is the triad of micrognathia, glossoptosis and cleft palate, without the ear and zygomatic anomalies.
• C. Apert syndrome combines craniosynostosis with symmetrical syndactyly of the hands and feet, which is its distinguishing feature.
• D. Correct. Treacher Collins syndrome, or mandibulofacial dysostosis, results from defective first and second branchial arch development, usually from TCOF1 mutations. It gives downslanting palpebral fissures with lower lid colobomas, zygomatic and mandibular hypoplasia, external ear malformation with conductive hearing loss, and often cleft palate.

Correct answer: D. Congenital syphilis

• A. Congenital rubella causes cataracts, cardiac defects and deafness, and may cause enamel defects, but not this specific tooth morphology.
• B. Tetracycline produces intrinsic banded discolouration but leaves crown morphology unchanged.
• C. Amelogenesis imperfecta is a hereditary enamel disorder affecting all teeth in both dentitions and does not alter crown shape in this notched, multicusped way.
• D. Correct. Hutchinson incisors and mulberry or Moon molars are dental stigmata of congenital syphilis, arising when Treponema pallidum disturbs the developing tooth germs. With interstitial keratitis and eighth nerve deafness they form Hutchinson's triad. The changes are permanent, since they occurred during crown formation.

Correct answer: B. Midface anomaly with a smooth philtrum and thin upper lip

• A. Microcephaly, not macrocephaly, is characteristic.
• B. Correct. The facial phenotype is midface hypoplasia with a smooth philtrum, a thin vermilion border of the upper lip and short palpebral fissures. Growth restriction, microcephaly and neurodevelopmental impairment complete the picture, and cleft palate occurs more frequently.
• C. Midface hypoplasia can create a relative Class III appearance, but true mandibular prognathism is not a defining feature.
• D. Supernumerary teeth belong to cleidocranial dysplasia and Gardner syndrome.

Correct answer: C. An autoimmune condition

• A. MS is not present at birth and does not arise from a developmental error. It typically appears between 20 and 40 years.
• B. A reactive process follows a defined local stimulus and resolves when that stimulus is removed, which does not describe MS.
• C. Correct. Multiple sclerosis is an autoimmune demyelinating disease in which T cells attack oligodendrocytes and the central nervous system myelin they produce. Relevant to dentistry, it can present with trigeminal neuralgia, particularly bilaterally or in a young patient, and facial weakness, sensory disturbance and dysphagia may follow.
• D. There is no neoplastic proliferation; the pathology is inflammatory demyelination with plaque formation.