AssessmentsSystemic lupus erythematosus (SLE): Pathology review
USMLE® Step 1 style questions USMLE
A 38-year-old woman comes to the clinic complaining of pain in her hands for several months. The pain is characterized by an intermittent aching in both of the wrists and the bases of the fingers that lasts for hours at a time. The patient also feels warm at night and has not had much of an appetite recently. The patient’s temperature is 37.6 C (99.6 F), pulse is 77/min, respirations are 14/min, and blood pressure is 145/85 mmHg. Physical examination shows mild symmetric swelling of the wrists, metacarpophalangeal, and proximal interphalangeal joints bilaterally, without tenderness on palpation. There are no skin lesions. Laboratory studies show the following:
Which of the following is the most common cause of death in patients with this condition?
At the internal medicine department, a 42 year old female named Mary shows up.
She complains of multiple skin lesions on the arms, chest and back.
She reports having these lesions for about 3 months.
In the past, she had similar lesions.
She reports morning stiffness involving her fingers and knees, as well as a history of multiple miscarriages.
Blood tests revealed pancytopenia as well as very high ESR and CRP.
She was positive for ANA and antiphospholipid antibodies.
Meanwhile, at the emergency department, a 25 year old man named Kyle shows up with flank pain and hematuria.
He has a history of migratory arthralgias and photosensitivity.
He was positive for ANA and double-stranded DNA antibodies, and also had low complement levels.
Blood tests revealed very high ESR and CRP, as well as high creatinine, so a urinalysis was performed, showing proteinuria and red blood cell casts.
Both individuals actually have very different presentations of the same disease, called Systemic Lupus Erythematosus.
This is a systemic, relapsing, and remitting autoimmune disease, where systemic means that essentially any tissue or organ can undergo inflammation; while relapsing and remitting, stands for periods of illness, called relapses or flares; and periods of remission during which there are few or no symptoms.
Essentially, B cells start producing antibodies which bind to nuclear antigens in our own cells.
The antibodies released by these B cells form antigen-antibody complexes and these complexes drift around in the blood until they deposit or stick to the vessel wall in all sorts of different organs and tissues like the kidneys, skin, joints, heart.
Deposited complexes then initiate a local inflammatory reaction, which causes damage through the activation of the complement system, which, after a huge cascade of enzyme activation, causes the cell to burst and die.
Eventually, this gets complement factors like C3 and C4 all used up.
A very high yield fact to remember is that this is a kind of type III hypersensitivity reaction.
Another high-yield fact is that because early complement proteins like C1q, C2 and C4 are all involved in removing those antigen-antibody complexes, individuals that lack any of these proteins are more likely to experience lupus.
Now, many patients also develop antibodies targeting other cells like red, white blood cells and platelets, leading to pancytopenia.
This is considered a type II hypersensitivity reaction.
Okay, the classic scenario involves a female of reproductive age, especially of African-American or Hispanic descent.
There are 11 key symptoms and findings you need to remember for lupus and we can divide them into 4 groups.
The first group are 3 symptoms that have to do with the skin.
The first is a malar rash, sometimes just called a “butterfly rash”, which is a rash over the cheeks that spares the nasolabial folds and appears after sun exposure.
Second is a discoid rash, which is chronic erythematous rash in sun-exposed areas like the arms and legs that are plaque-like or patchy redness that’s scaly and can cause severe scarring or hair loss.
Third, is a general photosensitivity of the skin, essentially a catch-all category for other rashes that happen to sun-exposed areas, typically only lasting a couple of days.
The next group involves 2 symptoms affecting the membranes.
Lupus can also damage the inner membrane or mucosa of various tissues, causing ulcers in the mouth or nose.
Next, there’s serositis which is inflammation of the serosa, which is like the outer membrane of an organ or tissue.
It can manifest as pleuritis, which is inflammation of the lining around the lungs and chest cavity; as peritonitis, which is inflammation of the lining of the abdomen, or as pericarditis, which is inflammation of the lining of the heart.
It’s worth noting that in addition to pericarditis, lupus can also cause inflammation of the myocardium, leading to myocarditis, or the endocardium, leading to Libman-Sacks endocarditis, where clumps of fibrin and immune cells form vegetations on the mitral or aortic valve.
What makes these vegetations special is that they can be present on either surface of the valve, but are usually on undersurface.
The third group includes 3 extraglandular manifestations.
First up is and two or more joints have to be inflamed.
The next one is evidence of kidney damage based on protein or cells in the urine.
It’s generally caused by diffuse proliferative glomerulonephritis, which is the most common and severe type of glomerulonephritis caused by immune complex deposition along the glomerular basement membrane.
The test question might show you or describe a light microscopy image with diffuse thickening of the glomerular capillary walls with characteristic "wire-loop" structures.
The final three are lab findings related to blood.
One of these is having autoantibodies against blood components causing cell destruction, and leading to conditions like anemia, thrombocytopenia, or leukopenia; while the tenth and eleventh findings have to do with having specific antibodies in the blood.
The next one is having positive serology for antinuclear antibody or ANA, which targets nuclear antigens.
Now a large proportion of patients with lupus have these, meaning this test is very sensitive, but it isn’t very specific, because it can be found in other autoimmune diseases.
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