Errors in First Aid for the USMLE (2007): Musculoskeletal System

As always, this comes from an email sent to the First Aid team. Please add any errors or suggestions in the comments section.

Musculoskeletal (all references from Merck Manual and Robbins Basic Pathology)

  1. P.326, Smooth muscle contraction
    1. This diagram shows Myosin light-chain phosphatase (MLCP) acting before contraction. Every other reference I have found details SMC contraction in the following steps
      1. Calcium binds calmodulin
      2. Calcium-calmodulin activates Myosin light chain kinase (MLCK)
      3. MLCK phosphorylates myosin, allowing a crossbridge to form
      4. Contraction follows
      5. MLCP dephosphorylates myosin, allowing for relaxation.
    2. I think this diagram should be changed in the following way:
      1. “Cross-bridge formation with contraction
      2. After the action of MLCP, “contraction” should be changed to ” relaxation.”
  2. P.327, Rheumatoid arthritis
    1. In RA, the DIP is completely spared. A small point, but the image of the Swan-neck deformity should be pointing to the involved joint (hyper-extended PIP) and not the DIP (normal).
  3. P.327, Osteopetrosis
    1. In addition to be called “marble bone disease,” this condition is frequently referred to as “Albers-Schonberg” disease. I think this should be mentioned.
    2. Osteopetrosis also presents with hepatosplenomegaly (secondary hematopoiesis due to loss of bone marrow) and cranial nerve palsies. I think both of these should be mentioned.
  4. P.327, Osteitis fibrosa cystica
    1. This disease is also often referred to as “von Recklinghausen’s disease of bone.”
    2. In the same way that alkaline phosphatase is raised in states of high osteoblastic activity, Tartrate-Resistant Acid Phosphatase (TRAP) levels are raised in states of high osteoclastic activity. I think it is worth mentioning both of these correlates in this section.
  5. P.328, Polyostotic fibrous dysplasia
    1. This disease is often referred to as McCune-Albright. I think the text should be changed to “(McCune-) Albright Syndrome”
  6. P.329, Gout
    1. I think it would be helpful to include “glucose-6-phosphatase deficiency (von Gierke’s)“.
  7. P.330, Scleroderma
    1. After the first bullet point, I think it should say, “Associated with anti-Scl-70 antibody against topoisomerase“.
  8. P.331, Skin disorders
    1. Atopic dermatitis has pruritic eruptions within skin flexures, not on flexor surfaces i.e. you would expect to see them within the elbow crease and around the neck instead of on the surface of the bicep and forearm.
    2. Seborrheic keratosis should include the common vignette descriptions of “ stuck-on appearance” and “greasy.”
  9. P.332, Primary bone disorders
    1. A constant feature of osteoid osteoma (in contrast to osteoblastoma and osteoma) is complaint of pain at the site of the lesion. I think that this should be briefly mentioned: “pt. complains of pain”
    2. A feature of Giant Cell tumor of bone is the complaint of arthritis in a young person (20-40 yoa). I think this should be briefly mentioned: “young pt. complains of ‘arthritis'”.
    3. Osteosarcoma has a bimodal peak in incidence, once in 10-20 year olds associated with Retinoblastoma, and once in the elderly following Paget’s disease of bone. Without this distinction, it makes no sense so list Paget’s disease here because this rarely (if ever) occurs in patients younger than 40. I think this should be changed to:
      1. “Most common primary malignant tumor of bone. Peak incidence in men 10-20 years old (associated with familial retinoblastoma). Smaller second peak in elderly (associated with Paget’s disease of bone, bone infarcts, radiation). Commonly found….”
    4. A feature of Ewing Sarcoma is the complaint of pain and warmth over the site of the lesion. I think this should be briefly mentioned.
  10. P.333, Other ANCA-associated vasculitides
    1. In the same way that the “Lesions are of different ages” in PAN, I think it is worth mentioning that the lesions are all of the same age in microscopic polyangiitis.
  11. P.335, NSAIDS
    1. I do not understand why there is no mention of Aspirin in this section.
  12. P.337, Immunosuppresive agents: sites of action
    1. I do not understand why Tacrolimus (FK506) and Cyclosporine (CSA) are shown as having completely non-overlapping sites of action since they inhibit the exact same pathway at the exact same step (one by binding cyclophilin, the other by binding FKBP).

Return to First Aid Errors page.

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13 Responses to Errors in First Aid for the USMLE (2007): Musculoskeletal System

  1. Sanjay Linganna says:

    I think that you (or Baby Robbins) are wrong w/ regards to ANCA and PAN (point number 10).

    Daddy Robbins (7th edition), page 539 states “About 30% of patients with PAN have hepatitis B antigen in their serum. There is no association with ANCA”

    I think you might be confusing PAN with mPAN (Microscopic Polyangiitis, also known as microscopic polyarteritis, hypersensitivity, or leukocytoclastic vasculitis).

    Page 539-540 of Daddy Robbins talks about mPAN: “In 70% of patients, p-ANCAs are present”.

    First Aid mentions this correct association btwn mPAN and pANCA at the bottom of page 333.

    Merck concurrs with Daddy Robbins, pages 275-276.

  2. I am wrong. Nice catch.

  3. smalley says:

    hows ur immuno goin on?
    are u content with rr immuno. i also have the same stuff but seems a lot short on basic explns
    gl

  4. Rapid Review Immuno is very short, but I’m past the point where I can really tell. I guess what I mean is that I can’t tell when something is missing, but I can tell when something that shouldn’t be there is. I was happy with their Immuno because I knew I was going to pick up anything else important from Path, Phys, Genetics, etc. I would buy the book again.

  5. Fernando says:

    Point 9, bullet 3. According to the Merck Manual (and pg. 312 of FA) multiple myeloma is the most common primary malignant tumor of bone and osteosarcoma is second most common. http://www.merck.com/mmpe/sec04/ch044/ch044c.html

  6. Nelson says:

    Regarding Fernando’s comment (which refers to #63 in the Word doc) – why would multiple myeloma be considered a primary bone malignancy? It is a hematopoietic stem cell malignancy…First aid (p312) says MM is the most common primary tumor arising *within* bone. I think that’s clear enough, and it seems like they’d present so differently clinically that it’d be a non-issue.

  7. Julie says:

    p.333–should mention that PAN is NOT associated with granulomas like Wegeners; also that PAN lesions favor branching points of arteries; Lastly, the last line under Churg-Strauss syndrome stating “often seen in atopic patients” should be followed by commonly has new onset or worsening of asthma preceding symptoms of vasculitis.

  8. stuart blackwood says:

    Regarding rheumatoid Arthritis I think First Aid was a bit brief leaving a few key buzz words commonly associated with RA which might come up on exams, namely:
    1. Baker’s cyst
    2. Caplan Syndrome;
    3. Felty’s Syndrome = Severe RA + Neutropenia and Splenomegaly.
    4. Treatment = 1st line NSAIDs for acute attacks (and do not prevent joint damage) Vs Methotrexate (the anchor drug to prevent further joint damage)

    and my personal favorite the Rheumatoid Pocket. –> HLADRB1 which plays a key role in some RA patients by allowing excessive antigen presentation to T-cells… even if rheumatoid pocket is not important i still think its cool…YES!!!

  9. Yvonne says:

    Figure 56 a/w RA seems to exemplify boutonniere deformity, not swan-neck deformity as described in the caption.

  10. JC says:

    p. 327. Osteopetrosis: The text should mention that these thick, marble-like bones are pathologically BRITTLE, making them prone to fracture.

    (I disagree that the eponyme “Albers-Schonberg” should be included in the text. There are too many eponyms in medicine!)

  11. What’s up i am kavin, its my first time to commenting anyplace, when i read this post i thought i could also create comment due to this good piece of writing.

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  13. Dwedoceve says:

    Hello! My name is Liam Bitner and I live in Fredericksburg,TX. I have read your blog post about Errors in First Aid for the USMLE (2007): Musculoskeletal System | the rumors were true and I want to say that I am quite impressed with your professionalism on the subject!

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