Two Rare Dermatology Cases: Methotrexate Toxicity and Cryofibrinogenemia

Conclusions

• The first case shows that severe mucocutaneous ulcerations, pancytopenia, and systemic symptoms can be caused by methotrexate toxicity even when the exposure is initially hidden or not volunteered by the patient.
• Low-dose methotrexate errors, especially accidental daily dosing, can produce marrow suppression, skin necrosis, and oral/GI toxicity while serum methotrexate levels may remain normal.
• When a complex case is not fitting the first-pass diagnosis, the objective findings should be reassembled systematically and the differential should be revisited from scratch rather than forcing a convenient explanation.
• Limited health literacy and fragmented medication histories are major risk factors for missing drug toxicity, so targeted questioning and collateral history are essential.
• The second case demonstrates that progressive digital ischemia is not synonymous with Raynaud’s phenomenon and requires a broad workup for vasculopathy, autoimmune disease, hypercoagulability, and hematologic malignancy.
• Skin biopsy can be crucial in digital ischemia, but its interpretation must be integrated with the full clinical and laboratory picture because thrombotic vasculopathy can mimic several other entities.
• Cryofibrinogenemia should be considered in unexplained digital ischemia, and it may be missed if clinicians only order cryoglobulin testing.
• Markedly abnormal free light chain studies and monoclonal protein testing should raise strong concern for plasma cell neoplasms such as multiple myeloma.
• Rare but important dermatologic and vascular manifestations can be the presenting clue to an underlying hematologic malignancy.
• Both cases emphasize that trusting colleagues is important, but clinicians must still independently verify the diagnosis when the presentation, workup, or response to treatment does not fully add up.