A 25-year-old woman comes to the office due to arthralgias in her hands for the last several months. The pain frequently involves her wrists and proximal finger joints bilaterally, and alternates between being worse in the wrists versus in the hands. The patient has no other medical problems and takes no medications. Complete blood count results are as follows:
| Erythrocytes | 3.2 million/mm3 |
| Platelets | 90,000/mm3 |
| Leukocytes | 3,200/mm3 |
Further evaluation reveals proteinuria and red blood cell casts. Which of the following is the most likely diagnosis?
Manifestations of systemic lupus erythematosus | |
Clinical |
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Laboratory |
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dsDNA = double-stranded DNA. | |
This patient has chronic migratory arthralgias, pancytopenia, and evidence of glomerulonephritis (ie, proteinuria, red cell casts). These findings are suspicious for systemic lupus erythematosus (SLE), an idiopathic autoimmune disorder that is most common in women.
Hematologic abnormalities are common in SLE. The most common cause of anemia is chronic inflammation (anemia of chronic disease); however, pancytopenia (as seen in this patient) can also occur due to autoantibodies against blood cell antigens (ie, type II hypersensitivity). Autoimmune hemolytic anemia in SLE is caused by IgG antibodies against erythrocytes; manifestations include spherocytosis, a positive direct Coombs test, and extravascular hemolysis. Antiplatelet antibodies in SLE can cause thrombocytopenia resembling immune thrombocytopenic purpura. Leukopenia can also occur, primarily due to antibody-mediated destruction of neutrophils.
Lupus nephritis is caused by immune complex deposition (ie, type III hypersensitivity) in the mesangium, subendothelial, and/or subepithelial spaces. Histopathology is variable but diffuse proliferative glomerulonephritis (class IV) is the most common pattern.
(Choice A) Ankylosing spondylitis is a chronic inflammatory arthritis involving the spine and sacroiliac joints. It presents with low back pain and stiffness. Common associated features include enthesitis, dactylitis, and uveitis, but renal and hematologic manifestations (other than anemia of chronic disease) are not common.
(Choices B, C, and E) Myelodysplastic syndromes and primary myelofibrosis are bone marrow disorders that occur most commonly in patients over age 50. Vitamin B12 deficiency can also cause impaired hematopoiesis. Although these disorders can cause pancytopenia, this patient's arthritis and nephritis are much more consistent with SLE.
Educational objective:
Systemic lupus erythematosus is an autoimmune disorder that occurs most commonly in women. Hematologic abnormalities are common; autoantibodies against blood cell antigens (ie, type II hypersensitivity) can cause pancytopenia (ie, anemia, thrombocytopenia, leukopenia). In contrast, lupus nephritis is caused by immune complex deposition (ie, type III hypersensitivity) in the glomeruli.