Cytoskeleton and elastin disorders: Pathology review

A 10 year old male, named Thomas, is brought to the clinic by his father because of a persistent fever, as well as a productive cough with dark, foul-smelling sputum. Upon further questioning, his father states that, since birth, Thomas has had multiple bouts of sinusitis and pneumonia, which required antibiotics. Upon chest auscultation, you realize that the heart sounds are heard on the right side of the chest! You then decide to order a chest X ray, which reveals that Thomas’ heart is in fact located on the right side of the chest! Finally, you get a CT scan, which reveals abnormally dilated airways.

Right after Thomas, you meet Sara, a 17 year old female who comes into the clinic complaining that her joints frequently slip out of place. On physical examination, her height is at the 90th percentile and weight at the 60th percentile for her age. In addition, you notice that her fingers and toes are abnormally long. Upon chest auscultation, you hear a diastolic murmur in the aortic area.

Based on the initial presentation, Thomas seems to have some sort of a cytoskeletal disorder, whereas Sara most likely has an elastin-related disorder.

Okay, before we start with cytoskeletal disorders, here’s a bit of physiology real quick! The cytoskeleton is an intracellular network of proteins, which allows each cell to maintain its shape, but also to move, contract, divide, and absorb or secrete molecules. Now, one of the protein structures in the cytoskeleton is microtubules. These are tiny hollow rods found at the base of cilia, which are hair-like structures on the surface of epithelial cells lining the respiratory and reproductive tracts.

Specifically, each cilium has microtubules arranged in a 9+2 pattern, meaning there are 9 microtubules doublets on the periphery, as well as two single central microtubules.

Now, in between the microtubules, there’s the dynein arm ATPase protein, which uses ATP to make microtubules slide past each other. This causes the cilium to bend and, thus, move back and forth in a wave-like motion, which is necessary to swipe out mucous secretions, debris, and foreign particles or pathogens. This function is especially important in the middle ear, paranasal sinuses, airways, and lungs.