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Decreased serum calcium levels and elevated phosphate levels
38%
14/37
Autoimmune destruction of pancreatic islet cells and elevated blood glucose levels
3%
1/37
Insulin insensitivity and elevated blood glucose levels
Bronzing of the skin and elevated blood glucose levels
51%
19/37
Kayser-Fleischer rings and decreased serum ceruloplasmin
0%
0/37
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This patient's presentation is consistent with a diagnosis of calcium pyrophosphate dihydrate deposition disease (CPPD), or pseudogout. Pseudogout is associated with hemochromatosis which presents with bronzing of the skin and diabetes from pancreatic damage. Additional diseases associated with pseudogout include: prior joint trauma, familial chondrocalcinosis, hyperparathyroidism, Gitelman's syndrome, gout, hypothyroidism, rickets, familial hypocalciuric hypercalcemia, hypomagnesemia, and hypophosphatasia. CPPD occurs most commonly in proximal joints (knee most common) of patients over 60 years of age. Radiographs reveal chondrocalcinosis, and joint aspiration shows positively-birefringent rhomboid-shaped crystals. In this case the association with hemochromtosis would prompt the clinician to order electrolytes, iron studies demonstrating an elevated free iron and ferritin, and a fasting blood glucose demonstrating hyperglycemia. When approaching this patient it is important to first know the diagnosis is a monoarticular arthritis which could be gout, pseudogout, or infectious arthritis. Given the lack of a sexual history and systemic signs, it seems less likely that this patient has an infectious arthritis. Regardless the next step in management is to perform arthrocentesis. Though the cell count and gram stain is not given, the actual results of a polarized light exam are given, which reveal positively birefringent, rhomboid crystals sealing the diagnosis of pseudogout. With the correct diagnosis in mind it is now important to know the associated diseases that could predispose one to pseudogout, most importantly hyperparathyroidism and hemochromatosis. This question requires an extra step in thinking of knowing the common presentation of certain diseases with the classic "bronze diabetes," of hemochromatosis given. Figure A is a polarized light microscopy showing calcium pyrophosphate dihydrate crystals from the synovial fluid of a patient with pseudogout; note the positively-birefringent rhomboid-shaped crystals. Illustration A demonstrates chondrocalcinosis, a radiographic finding seen in pseudogout. Illustration B explains the difference between positive and negative birefringence; yellow means parallel to the light axis. Incorrect Answers: Answer 1: Decreased calcium and increased phosphate are classic findings associated with hypoparathyroidism. Hyperparathyroidism (not HYPOparathyroidism) is associated with pseudogout. Answers 2,3: Autoimmune destruction of islet cells (Type I DM) and insulin insensitivity (Type II DM) are not associated with pseudogout. Answer 5: Kayser-Fleischer rings and decreased serum ceruloplasmin are classic findings associated with Wilson's disease which is not associated with pseudogout. In joint pain, if an infection is suspected, culture and gram staining of synovial fluid followed by initiation of empiric antibiotics is required. Polarized light microscopy is the best modality for detecting crystal formation in the joint. Radiographs may only be helpful in select conditions; a normal appearing radiograph should not be construed as an absence of an underlying problem (1).
4.1
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