Clinical History
A 24-year-old woman presented with a slowly progressive muscle weakness. She first noted difficulty in getting out of a chair some months ago and now has difficulty climbing stairs. The weakness is not made significantly worse by repetitive activity, nor does it go away with rest. She also noted some muscle pain associated with this illness. On physical examination, she has moderate proximal muscle weakness. Laboratory findings include a serum creatine kinase of 3534 U/L. An electromyogram demonstrates a combination of myopathic features and fibrillation potentials.
The image demonstrates a marked inflammatory cell infilltrate with muscle fiber degeneration.
-
- Which of the following serologic test findings is most likely to be present in this case?
- A. Anti-histidyl tRNA synthetase
- B. Anti-double stranded DNA
- C. Anti-parietal cell antibody
- D. Anti-DNA topoisomerase I
- E. Anti-ribonucleoprotein
|
Answer: A The findings suggest polymyositis, because of the myalgias and weakness.
Further history:
A month later she has a faint violet coloration to the skin of her eyelids and cheeks, but without significant erythema, and it is not made worse by sun exposure. She continues to have muscular weakness. A muscle biopsy is performed. By light microscopy with H&E staining, there is focal inflammation with lymphocytes, along with rare scattered plasma cells and neutrophils. Some of the inflammation is endomysial. Some of the muscle fibers show degeneration with necrosis. A few muscle fibers appear to be regenerating.
-
- Which of the following pathologic mechanisms most likely accounts for these histologic findings?
- A. Antigen-antibody complexes
- B. Infection by Staphylococcus aureus
- C. Lack of a cell membrane stabilizing protein
- D. Wallerian degeneration
- E. Antibody-mediated cytotoxicity
|
Answer: E The findings in the skin suggest dermatomyositis. There is T-cell dependent stimulation of B cells to produce antibody that is directed against the muscle fibers and small capillaries with a vasculitis. This antibody also produces vascular damage. Polymyositis mainly results from the cytotoxic effects of CD8+ lymphocytes recognizing HLA class 1 MHC molecules on sarcolemmal membranes.
-
- Which of the following organs is most likely to be affected by this condition?
- A. Liver
- B. Brain
- C. Kidney
- D. Heart
- E. Adrenal
|
Answer: C If the myoglobinuria is severe with rhabdomyolysis from inflammation and necrosis, acute tubular necrosis and renal failure may occur.
-
- In adults with this condition, which of the following underlying diseases is more likely to occur?
- A. Membranoproliferative glomerulonephritis
- B. Atherosclerotic heart disease
- C. Gastric adenocarcinoma
- D. Hyperparathyroidism
- E. Pulmonary emphysema
|
Answer: C There is an increased risk for visceral malignancies in persons who have polymyositis-dermatomyositis.
Further history:
Her condition does not improve. How is consent for her treatment obtained when she no longer has capacity?.
There are two issues to discuss:
First: if the disease has progressed to where the patient no longer can make decisions for herself, who should make the decisions and how? The answer is that there is a clear order laid out in the law: a court appointed guardian first, if there is one, then someone named by the patient when she had capacity (this is called a surrogate under Florida law), third is a spouse if there is one, then adult children (the majority must agree on any decision, if there are more than one), then parents, then a close friend. The point of the ranking is not any oversimplified claim of a socially determined kinship status, but seeking the persons who know the patient the best as peers, and are most likely to know and be willing, or more likely, to make the decision the patient herself would have made.
Second: a patient with this disease often has years from diagnosis until losing capacity. During that time she should have been asked to make out advance directives, including putting down on paper some ideas of what she would want to be her goals of treatment, and at what point she would not want further treatment because none of her goals can be achieved. The advance directives should also include naming a surrogate, and making sure the surrogate understands the wishes of the patient.
|
|
