USMLE Step 1

USMLE Step 1 QUESTION of the DAY!

A 12 year-old boy presents to the ER with his fifth fracture in 2 years. During the H+P you find the boy to be partially deaf and also with blue sclerae. This boys diagnosis is primarily:
A) Autosomal recessive
B) Autosomal dominant
C) X-linked recessive
D) X-linked dominant
E) Mitochondrial inheritance

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Answer: B) Autosomal Dominant. This boy has osteogenesis imperfecta. An autosomal dominant disorder caused by a variety of gene defects resulting in abnormal collagen synthesis. It is characterized by multiple fractures, blue sclerae, dental imperfections, and hearing loss.


USMLE Step 1 D.O.C. of the day!

Drug of choice for

Chlamydia pneumoniae causing pneumonia

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Tetracycline


USMLE Step 1 Fact of the Day!

Bug Profile: Mycoplasma pneumoniae
- causes atypical pneumonia
- no cell wall = no gram stain results
- only bacteria with cholesterol in cell membrane (mycoplasma)
- produces hydrogen peroxide which damages respiratory tract
- Dx by labs takes too long to be clinically useful
- DOC: Erythromycin but tetracycline is effective