Question

The clinical photograph and slit-lamp image show iris hamartomas (Lisch nodules) with skin findings in a child with neurofibromatosis type 1 (NF1). Which cutaneous lesion is the earliest and most characteristic feature of NF1?

• A. Café-au-lait macules
• B. Ash-leaf (hypopigmented) macules
• C. Port-wine stain
• D. Shagreen patch

Hint:

Lisch nodules + skin patches = NF1; its earliest skin marker is a flat light-brown macule.

Answer 1

The Correct Option is A

Step 1: Recognise the condition.
Lisch nodules (iris hamartomas) on slit-lamp plus the clinical skin photo point to neurofibromatosis type 1 (NF1), an autosomal dominant neurocutaneous disorder caused by mutations in the NF1 gene (neurofibromin, chromosome 17).

Step 2: Recall the diagnostic criteria.
NF1 diagnosis needs ≥2 of: \(\ge\)6 café-au-lait macules, \(\ge\)2 neurofibromas or 1 plexiform neurofibroma, axillary/inguinal freckling (Crowe sign), \(\ge\)2 Lisch nodules, optic glioma, a distinctive bony lesion, and a first-degree relative with NF1.

Step 3: Identify the earliest cutaneous sign.
Café-au-lait macules (CALM) are flat, well-demarcated light-brown patches that usually appear first, often at birth or in infancy, before neurofibromas develop.

Step 4: Why the others are wrong.
• Ash-leaf macules and Shagreen patch are features of tuberous sclerosis, not NF1.
• Port-wine stain is seen in Sturge-Weber syndrome.

Key fact: The hallmark and earliest skin lesion of NF1 is the café-au-lait macule (\(\ge\)6 of \(\ge\)15 mm is a diagnostic criterion).