NephroQuiz: a fishy rash.

NephroQuiz is curated by BMC Nephrology Editorial Board Members from Johns Hopkins University, Dr. Hanouneh and Dr. Cervantes. It aims to engage readers with clinical vignettes and problem solving. The USMLE-style questions are designed to test knowledge and engage with published literature.
NephroQuiz: a fishy rash.
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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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