Differential Diagnosis
The patient's presentation is complex, with 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 firm, raised whitish border, and are circular, which is consistent with morphea. The presence of extensive fibrosis and a significant amount of fibroblasts on skin biopsy also supports this diagnosis. Morphea is a form of localized scleroderma that can cause skin thickening and fibrosis.
- Other Likely Diagnoses
- Nephrogenic Systemic Fibrosis (NSF): Although the patient's kidney function is normal, NSF can occur in patients with normal kidney function. The presence of extensive fibrosis and a significant amount of fibroblasts on skin biopsy, as well as the patient's unexplained weight loss, make NSF a possible diagnosis.
- Scleromyxedema: This is a rare skin condition characterized by lichenoid papules, scleroderma-like skin thickening, and fibrosis. The patient's skin sores and biopsy findings are consistent with scleromyxedema.
- Chronic Cutaneous Lupus Erythematosus: Although the patient has had several lab tests to rule out lupus, chronic cutaneous lupus erythematosus is still a possible diagnosis. The patient's skin sores and biopsy findings, as well as the presence of mild normocytic anemia, make this diagnosis possible.
- Do Not Miss Diagnoses
- Cutaneous T-Cell Lymphoma (CTCL): CTCL can present with skin lesions that are similar to the patient's sores. A diagnosis of CTCL would require a skin biopsy with immunohistochemical staining for T-cell markers.
- Lymphoma: The patient's unexplained weight loss and mild normocytic anemia make lymphoma a possible diagnosis. A lymph node biopsy or imaging studies would be necessary to diagnose lymphoma.
- Infectious Diseases (e.g. Leishmaniasis, Blastomycosis): Although the patient has never left the United States, it is still possible that he has an infectious disease that is causing his symptoms. A diagnosis of an infectious disease would require cultures, serologies, or molecular testing.
- Rare Diagnoses
- Eosinophilic Fasciitis: This is a rare condition characterized by inflammation and fibrosis of the fascia. The patient's skin sores and biopsy findings, as well as the presence of mild normocytic anemia, make this diagnosis possible.
- Panniculitis: This is a group of conditions characterized by inflammation of the subcutaneous fat. The patient's skin sores and biopsy findings are consistent with panniculitis.
Recommended Lab Tests and Studies
To further evaluate the patient's condition, the following lab tests and studies are recommended:
- Immunohistochemical staining for T-cell markers on a skin biopsy to rule out CTCL
- Lymph node biopsy or imaging studies to rule out lymphoma
- Cultures, serologies, or molecular testing to rule out infectious diseases
- Antinuclear antibody (ANA) test to rule out lupus
- Extractable nuclear antigens (ENAs) to rule out lupus
- Complement levels to rule out lupus
- Imaging studies (e.g. MRI, CT scan) to evaluate the extent of fibrosis and to rule out other conditions
- Skin biopsy with special stains (e.g. Alcian blue, colloidal iron) to evaluate for mucin deposition and to rule out other conditions
Justification for Each Diagnosis
Each diagnosis is considered based on the patient's symptoms, lab results, and biopsy findings. The single most likely diagnosis, morphea, is considered due to the patient's skin sores and biopsy findings. The other likely diagnoses, NSF, scleromyxedema, and chronic cutaneous lupus erythematosus, are considered due to the patient's unexplained weight loss, mild normocytic anemia, and skin biopsy findings. The do not miss diagnoses, CTCL, lymphoma, and infectious diseases, are considered due to the patient's unexplained weight loss, mild normocytic anemia, and skin biopsy findings. The rare diagnoses, eosinophilic fasciitis and panniculitis, are considered due to the patient's skin sores and biopsy findings.