Paraneoplastic Trichomegaly as a Harbinger of Metastatic Renal Cell Carcinoma: A Case Report.

Renal cell carcinoma (RCC) is a common malignancy, often diagnosed incidentally on cross-sectional imaging. While classic symptoms such as flank pain, hematuria, and a palpable abdominal mass are well-known, RCC may present with more insidious findings. Here, we describe a case of paraneoplastic trichomegaly as the initial manifestation of metastatic RCC. A man in his 60s presented with progressive eyelash lengthening and mild hypertrichosis of the extremities and beard. Medication review and initial endocrine workup were unrevealing. Laboratory tests showed iron deficiency anemia, and subclinical hematuria was noted on urinalysis. Imaging revealed a right renal mass and retroperitoneal lymphadenopathy. Biopsy confirmed clear cell RCC. The patient was treated with neoadjuvant immunotherapy followed by radical nephrectomy. His trichomegaly improved with treatment. Unfortunately, he experienced disease progression and passed away 19 months later due to thrombotic complications of metastatic RCC. Trichomegaly is a dermatologic finding typically associated with congenital syndromes, drug effects, or HIV. Its paraneoplastic occurrence is exceptionally rare, and the molecular mechanisms driving paraneoplastic hypertrichosis remain unclear. This case emphasizes that occult malignancy should be considered in the setting of unusual mucocutaneous findings.