Musculoskeletal System Cheat Sheet | Lecture Note

University:
The University Of Western Ontario
Course:
Pathology 3500B | Human Pathology
Academic year:

2023
Views:

311

Pages:

3
Author:

Kyuwon J.

● Musculoskeletal anomalies are not rare ○ 5% of newborns tends to have congenital defects ■ limb deformities ■ dyspalsias ■ structural abnormalities ○ commonly they are not present immediately ■ requires growth to make defect manifest Genetics in Musculoskeletal Developments ● Single gene inheritance ○ principle of Mendel ○ autosomal dominant ■ one abnormal allele is sufficient for the phenotypical characteristics ○ Autosomal recessive ■ two abnormal allele is needed ○ X-linked dominant/recessive ● Chromosomal abnormalities ○ Deletion ○ Duplication ○ Translocations ○ Could affect multiple genes in syndromic musculoskeletal defects ● Polygenic/multifactorial inheritance ○ Could involve small genetic variants + environmental triggers ○ Scoliosis , hip dysplasia ○ Liability threshold model Inheritance patterns ● Autosomal Dominant (AD) ○ One abnormal allele ■ achrondroplaia ■ Marfan syndrome ■ Osteogenesis impereta ○ 50% chance of transmission towards offspring ○ No sex predominance ● Autosomal Recessive (AR) ○ Both parents are unaffected but carriers ■ Metabolic bone disease ● Inform errors on metabolism ○ 25% offspring affected 50% carriers 25% unaffected ○ No sex preference X-linked Dominant (XLD) ● Hypophosphatemic rickets ● Affected mother ○ 50% children affected ○ Both sexes ● Affected father ○ All daughters affected, no son affected ■ Because father gives Y chromosomes to sons ● X-linked Recessive (XLR) ○ Duchenne muscular dystrophy ○ Hemopillia ○ Males affected, females are carriers ■ Mild symptoms on females are also seen ○ Father passes gene to all daughter (becomes carriers) never to son Genetic counseling ● Pedigree is essential on identifying inheritance patterns ○ Likelihood on recurrence in siblings ○ Carrier status in family member ○ Reproductive risk ● Recurrence in siblings ○ AD ■ 50% chance once one of the parent is affected ○ AR ■ 25% chance if both parents are carriers ○ X-linked ■ Risk differs between sexes male and females have different risk levels ○ Multifactorial ■ Risk of recurrence will increase ■ Number and severity will affect the level of recurrence