A 28-year-old man presents with a 2-year history of progressive skin lesions. Examination reveals multiple flesh-colored papules and nodules on the face, trunk, and extremities. He also reports a family history of similar skin lesions in his father and paternal grandfather. On dermoscopy, the lesions show a characteristic "Swiss cheese" appearance with central invaginations. Additionally, he has a history of recurrent infections and delayed wound healing. What is the most likely diagnosis?

Explanation

## Diagnosis: Neurofibromatosis Type 1 (NF1) ### Clinical Presentation The patient presents with multiple flesh-colored papules and nodules with a characteristic "Swiss cheese" appearance on dermoscopy, which is pathognomonic for neurofibromas. The progressive nature, family history (autosomal dominant inheritance), and recurrent infections are classic features of NF1. ### Key Diagnostic Features of NF1 **Key Point:** NF1 is an autosomal dominant condition caused by mutations in the NF1 gene (chromosome 17q11.2), which encodes neurofibromin, a tumor suppressor protein. | Feature | NF1 | |---------|-----| | **Cutaneous manifestations** | Neurofibromas (localized, diffuse, plexiform), café-au-lait spots (≥6 spots >15 mm) | | **Inheritance** | Autosomal dominant (50% penetrance, 100% expressivity) | | **Dermoscopy** | Swiss cheese appearance (central invaginations) | | **Associated complications** | Optic nerve gliomas, pheochromocytoma, malignant peripheral nerve sheath tumors (MPNST), increased infection risk | | **Malignancy risk** | Lifetime risk of MPNST ~8–13% | ### Pathophysiology Neurofibromin loss leads to uncontrolled Ras signaling, resulting in: 1. Uncontrolled cell proliferation 2. Impaired apoptosis 3. Increased susceptibility to malignant transformation **Clinical Pearl:** The recurrent infections and delayed wound healing in this patient suggest impaired immune function, a known complication of NF1 due to neurofibromin's role in immune cell regulation. **High-Yield:** Diagnostic criteria for NF1 (NIH consensus, 1988) require 2 or more of: - 6 or more café-au-lait spots (>15 mm in adults) - 2 or more neurofibromas of any type - 1 plexiform neurofibroma - Optic nerve glioma - 2 or more iris Lisch nodules - Distinctive osseous lesion (sphenoid dysplasia, long bone dysplasia) - First-degree relative with NF1 ### Management - Regular surveillance for malignancy (especially MPNST) - Genetic counseling and family screening - Ophthalmologic evaluation for optic nerve gliomas - Screening for pheochromocytoma (24-hour urine metanephrines) [cite:Robbins 10e Ch 7]