Recap and Resources on Case conference 8/18/2024
On Monday, Gwen presented an interesting case with livedo reticularis, and reviewed relevant topics including retiform purpura, skin lesions in vasculitis/vasculopathy, and several related diagnoses.
Diagnostic journey/Teaching point recap:
— We have a 46-yo patient presenting with lacy rash in her lower extremities, gradually worsening over many years. After a quick review of how to characterize rash, we recognize it as livedo reticularis.
— We reviewed similar conditions along the same spectrum, including livedo racemosa, and retiform purpura. While these terms may be confusing, it could be helpful to think the livedo reticularis -> livedo racemose -> retiform purpura as a spectrum from more physiologic slowing of blood flow to more pathologic and irreversible ischemia involving skin blood vessels. They are usually a result of vessel occlusion or vessel damage.
— From there, we discussed the Ddx and workup in this patient. I found this UpToDate article on retiform purpura helpful in creating a framework, which I also summarized here. On the far right end of the spectrum, the Ddx would include infections that can mimic vasculitis such as invasive fungal infection and endocarditis +/- DIC, which does not apply to this patient given the overall clinical course. We considered many of the other Ddx: thrombosis as a result of antiphospholipid syndrome (APS) and other hypercoagulable conditions, intravascular protein deposition due to cryoglobulinemia/cryofibrinogenemia/paraproteinemia, and vasculitis from autoimmune diseases (eg, RA, SLE, dermatomyositis) or systemic vasculitis (PAN, ANCA-associated vasculitis, cryoglobulinemic vasculitis). We took relevant history (eg, pregnancy history), and reviewed workup for the above Ddx, which were all negative. The initial skin biopsy was also unrevealing.
— The patient ultimately underwent a repeat skin biopsy that showed fibrin thrombi, without evidence of conventional vasculitis. She was given the Dx of livedoid vasculopathy (which is often associated with the above Ddx), and treated with DOAC, with improvement in symptoms. We discussed that while vasculitis is less likely, it is appropriate to continue watching out for APS given the strong association. Indeed, the specialist has recommended repeating APS antibodies every few months, and educated patient/family on symptoms such as stroke.
— We reviewed how to diagnose APS (traditionally, clinical [vascular/pregnancy] + antibodies [“ABC”]). It is helpful to also review the newest 2023 ACR/EULAR APS classification criteria to be aware of the various presentations of APS.
— We also did some rash quiz on various skin manifestations of vasculitis/vasculopathy. Eg, recognize non-retiform palpable purpura as a sign of small-vessel vasculitis.
Additional resources:
1. Here is a recent CPSolvers podcast reviewing Ddx for retiform purpura through an interesting case, with discussion around the final Dx (one of the above)!
2. Can you recall another diagnosis Gwen taught us that must be considered in this patient? As promised, here is an inspiring story that features this diagnosis - written by a PGY-3 resident who is regarded as Dr. House in the CPSolvers community. Hope it will spark your interest in diagnostic reasoning!