A 51-year-old man presented for evaluation of a newly developed rash (xerosis with hyperpigmented scaly lesions on his arms, legs, abdomen, and back). Skin biopsy showed hyperkeratosis with non-necrotising granulomas. He had no medical history, did not report any nausea, vomiting, chest pain, dyspnea, or urinary symptoms. On examination his blood pressure was 125/75 mmHg, pulse rate was 85 beats per minute, and his oxygen saturation was 96%.
Laboratory investigations showed creatinine 6.27 mg/dL (normal range 0.67–1.17; a baseline measurement 2 months before he presented was 0.9), sodium 137 mmol/L (normal range 136–145), potassium 3.8 mmol/L (normal range 3.5–5.1), bicarbonate 22 mmol/L (normal range 22–29), calcium 15.1 mg/dL (normal range 8.6–10.2), albumin 4.3 g/dL (normal range 3.5–5.2), ionized calcium 1.91 mmol/L (normal range 1.17–1.38), parathyroid hormone (PTH) 9.1 pg/mL (normal range 18.4–80.1), PTH-related protein 3.4 pmol/L (normal range 0.0–2.3), 1,25-dihydroxyvitamin D 97.3 pg/mL (normal range 19.9–79.3), and angiotensin-converting enzyme 120 U/L (normal range 16–85).
Urinalysis was positive for proteinuria with a urine protein-to-creatinine ratio of 0.92. Further serology workup showed the following: negative hepatitis B virus, hepatitis C virus, and HIV serologies, normal C3 and C4, undetectable antinuclear antibodies (ANAs), anti-double stranded DNA antibodies titer of <1:10 (normal <1:10), negative antineutrophil cytoplasmic antibodies (ANCAs), serine protease 3 antibodies (PR3-ANCAs) titer of 0 AU/mL (normal 0–19), myeloperoxidase antibodies (MPO) titer of 0 AU/mL (normal 0–19), and phospholipase A2 receptor (PLA2R) antibody titer of <1:10 (normal <1:10).
Kidney biopsy (shown above) was performed with: light microscopy hematoxylin and eosin stain (A), light microscopy periodic acid methenamine silver stain (B), IgG Immunofluorescence microscopy (C), electron microscopy (D).
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