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Autosomal dominant
68%
58/85
Autosomal recessive
19%
16/85
Mitochondrial
1%
1/85
X-linked dominant
6%
5/85
X-linked recessive
5%
4/85
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This clinical presentation is consistent with multiple endocrine neoplasia, type IIB (MEN IIB), which is inherited in an autosomal dominant fashion. MEN IIB is associated with the presence of pheochromocytoma (unilateral or bilateral), medullary thyroid carcinoma (calcitonin secreting), mucosal and intestinal neuromas, and a Marfanoid habitus. Patients with MEN IIB also have development abnormalities, a decreased upper/lower body ratio, skeletal deformations (kyphoscoliosis or lordosis), and joint laxity. Generally, MEN II is sub-classified into three distinct syndromes: MEN IIA, MEN IIB, and familial medullary thyroid cancer. MEN IIA and IIB share medullary thyroid carcinoma and pheochromocytomas in their presentation. The genetic defect in these disorders involves the RET proto-oncogene on chromosome 10. While MEN IIB is generally autosomal dominant in its transmission, de novo mutations are also possible. Cohen discusses dermatologic manifestations of MEN and other syndromes associated with malignancy. MEN type IIB is associated with mucocutaneous neuromas. The presence of these lesions on physical exam, in the context of other tumor-associated symptoms, should prompt consideration of the diagnosis of MEN type IIB syndrome. Genetic counseling is central to the care for this population. Pasquali et al. state that patients with MEN have a lifetime risk of developing medullary thyroid carcinoma that is more than 95%. There are strong genotype-phenotype correlations within a variety of specific RET gene mutations that have important implications for the age at which prophylactic thyroidectomy should occur and whether screening for pheochromocytoma or hyperparathyroidism (seen in MEN IIA) is necessary. Figure A shows the long, tapered fingers suggestive of a Marfanoid habitus. Figure B shows mucosal neuromas affecting the tongue, a distinctive feature of MEN IIB, which occur in almost all patients. Figure C exhibits kyphosis, a skeletal abnormality seen in MEN IIB. Illustration A provides a schematic overview of MEN I, IIA, and IIB. Illustration B exhibits the gross pathology and histopathology of medullary thyroid carcinoma, which secretes calcitonin. Incorrect Answers: Answers 2-5: MEN IIB is generally inherited in an autosomal dominant manner, or occurs as a result of de novo mutations in the RET proto-oncogene on chromosome 10.
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