Clinical History
This patient is a newborn male born at 27 wks, 2 days gestation. 25y.o. mother is G1P1 w/ no significant past medical history. After prenatal testing, Ultrasound shows arthrogryposis of the bilateral lower extremities and aminocentesis- chromosomal micro duplication of 22q11 (near the DiGeorge locus). Apgar scores 0 and 1 and 5 minutes (no movement). An autopsy was performed following death on day 2, and it showed that lungs were immature (20% expected weight), and bilateral clubfeet.
Question:
Describe the muscle and nerve.
A. Fetal type IIC predom.
B. Denervation; axonopathy
C. Denervation; dismyelin.
D. Congenital myopathy
Answer:
The answer is A. Fetal type IIC predom.
Type IIC Fibers; Normal Nerve
Normal muscle at 27 to 28 weeks gestation
- Type IIC fibers (dark on both fast and slow-myosin) predominant
- Type I fibers (dark on slow-myosin only) few, but larger
Peripheral nerve myelinated before central nervous system
- Gomori trichrome – normal, back-to-back red “bubbly” myelin
- Neurofilament immunohistochemistry – normal mix of large & small fibers
Lack of movement, arthrogryposis & club feet not explained by muscle findings
- Brain autopsy: periventricular leukomalacia (PVL) – likely CNS etiology
- PVL is a known cause of cerebral palsy
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