Differential Diagnosis
The patient's presentation is complex, with consistently elevated IgG4 levels, skin sores that fail to heal, and unexplained weight loss. The following differential diagnoses are considered:
- Single Most Likely Diagnosis
- Morphea: The patient's skin sores have a characteristic firm, whitish border and leave an atrophic white patch after healing, which is consistent with morphea. The presence of extensive fibrosis and a significant amount of fibroblasts in the skin biopsies also supports this diagnosis.
- Other Likely Diagnoses
- Scleroderma: The patient's skin sores and fibrosis are similar to those seen in scleroderma. However, the absence of other systemic symptoms such as esophageal dysmotility or pulmonary fibrosis makes this diagnosis less likely.
- Chronic Cutaneous Lupus: The patient's skin sores and scarring are similar to those seen in chronic cutaneous lupus. However, the absence of other systemic symptoms such as joint pain or kidney disease makes this diagnosis less likely.
- Lymphoma: The patient's unexplained weight loss and elevated IgG4 levels could be indicative of lymphoma. However, the absence of other symptoms such as lymphadenopathy or night sweats makes this diagnosis less likely.
- Do Not Miss Diagnoses
- Cutaneous T-Cell Lymphoma: This diagnosis is important to consider due to the patient's skin sores and unexplained weight loss. A skin biopsy with immunohistochemical staining for T-cell markers would be necessary to rule out this diagnosis.
- Infectious Diseases (e.g. Leishmaniasis, Cutaneous Tuberculosis): Although the patient has never left the United States, it is still important to consider infectious diseases that could cause skin sores and unexplained weight loss. A thorough travel and exposure history, as well as diagnostic tests such as PCR or culture, would be necessary to rule out these diagnoses.
- Rare Diagnoses
- Nephrogenic Systemic Fibrosis: This diagnosis is characterized by fibrosis of the skin and other organs, and is often associated with elevated IgG4 levels. However, the patient's normal kidney function and lack of other systemic symptoms make this diagnosis less likely.
- Eosinophilic Fasciitis: This diagnosis is characterized by inflammation and fibrosis of the fascia, and is often associated with elevated IgG4 levels. However, the patient's lack of eosinophilia and other systemic symptoms make this diagnosis less likely.
Recommended Lab Tests and Procedures
- Skin biopsy with immunohistochemical staining: To rule out cutaneous T-cell lymphoma and other diagnoses.
- PCR or culture for infectious diseases: To rule out infectious diseases such as leishmaniasis or cutaneous tuberculosis.
- Serum protein electrophoresis (SPEP): To evaluate for monoclonal gammopathy, which could be associated with lymphoma or other diagnoses.
- Imaging studies (e.g. CT or MRI): To evaluate for lymphadenopathy or other systemic symptoms that could be indicative of lymphoma or other diagnoses.
- Autoantibody panel: To evaluate for autoimmune diseases such as scleroderma or lupus.
- IgG4 level monitoring: To monitor the patient's IgG4 levels and adjust treatment accordingly.