Case 33: Pathology

Case 33 Index

The skin biopsy results are shown below:

What do you see in the biopsy above?
Granuloma formation
Incorrect, this specimen does not show granuloma formation or significant cellular infiltration.
Calcification of arteries
Correct! Calcification is a defining feature of this condition, involving the small arteries and arterioles.
Gram negative bacilli
Bacteria are not visualized in this biopsy specimen. Try again!
Which stain has been used in the image above?
Jones methamine silver stain
This stain is used to better visualize collagent structures, which appear black. Try again!
Masson’s trichrome stain
This stain is used to identify areas of fibrosis. Pick again!
von Kossa stain
Correct! The von Kossa stain can used to identify calcium phosphate deposits. The silver ions in the stain react with phosphate. Photochemical degradation of silver phosphate to silver then occurs under light illumination
Immunohistochemistry (IHC) stain for C4d
C4d deposition may occur in the setting of classical complement pathway activation (i.e. antibody mediated rejection of a transplant). This is unlikely here, try again!
What are the best initial steps in management (several may be correct)?
Surgical debridement
This would not be the best initial step. Debridement is often avoided altogether, as manipulation can increase the risk of ulceration, new or worsening necrosis, or super-infection. Try something else first!
Increase sevelamer
It will be crucial to bring down this patient’s phosphate level and closely manage her hyperparathyroidism. Non-calcium containing phosphate binders should be used, and compliance should be encouraged.
Wound care consult
Absolutely! Expert wound care will be crucial in this condition.
Consider changing warfarin to a different anticoagulant
Correct! Warfarin is a risk factor for this condition and is implicated in its pathogenesis due to its inhibition of vitamin-K dependent pathways. This patient should be off warfarin, and an alternative should be discussed with the multidisciplinary team.
Initiate antimicrobial therapy
While this condition has very high risk of super-infection, these lesions do not appear to be actively infected at this time.
Initiate intra-lesional steroid injections
There is no indication for steroids (systemic, topical, or intra-lesional) in this condition, and local trauma should be avoided.
Stop oral Vitamin D
Vitamin D supplementation can lead to increased calcium absorption from the GI tract, leading to higher serum calcium levels which can worsen this condition.

In addition to the above interventions, sodium thiosulfate is initiated on dialysis.

What are the important risks to counsel the patient on regarding sodium thiosulfate (several may be correct)?
Metabolic alkalosis
Sodium thiosulfate has actually been shown to cause an elevated anion-gap metabolic acidosis, which can in some cases be severe.
GI side effects
Nausea and vomiting are common side effects of sodium thiosulfate therapy.
Sodium thiosulfate can cause hypotension, and blood pressure should be monitored closely.
Immunosuppression and increased risk of infections
Sodium thiosulfate has not been shown to cause suppression of the immune system.
While sodium thiosulfate can cause headache or confusion/disorientation, seizure is not one of the known adverse effects.

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Case 33 Index
Case 33 Introduction
Case 33 Physical Exam

Case 33 Diagnostic Testing