Lisch nodules - iris hamartomas seen in neurofibromatosis.

Two or more Lisch nodules (pigmented iris hamartomas)

An important difference is the absence of tumor growths (Lisch nodules and Neurofibromas which are common in NF-1) in LS.

Features common in neurofibromatosis - Lisch nodules, bone abnormalities, neurofibromas, optic pathway gliomas and malignant peripheral nerve sheath tumors - are absent in this condition.

Watson syndrome is an autosomal dominant condition characterized by Lisch nodules of the ocular iris, axillary/inguinal freckling, pulmonary valvular stenosis, relative macrocephaly, short stature, and neurofibromas.

A Lisch nodule is a pigmented hamartomatous nodular aggregate of dendritic melanocytes affecting the iris, named after Austrian ophthalmologist Karl Lisch (1907-1999), who first recognized them in 1937.