has material basis in germline mutation in ACTB melanocytic nevus Becker nevus syndrome https://github.com/monarch-initiative/mondo/issues/6877 https://rarediseases.info.nih.gov/diseases/3856/becker-nevus-syndrome https://www.malacards.org/card/becker_nevus_syndrome Becker nevus syndrome is characterized by the presence of a Becker nevus in association with underdevelopment (hypoplasia) of the breast or other skin-related, muscular, or skeletal defects, all of which usually involve the same side of the bodyas the nevus (ipsilateral). Specific signs and symptoms in addition to the nevus may include ipsilateral breast hypoplasia; skeletal abnormalities such ashypoplasia of the shoulder girdle, scoliosis, fused ribs, and ipsilateral shortness of the arm; and several other features. Thecondition is thought to be sporadic (occurring in individuals with no history of the condition in the family). Treatment varies depending upon the specific symptoms present and the extent of the condition in the affected individual. hairy epidermal nevus syndrome GARD:0005901 UMLS:C1858042 Orphanet:64755 MONDO:0011500 OMIM:604919 pigmentary hairy epidermal nevus MESH:C565735 MEDGEN:347608 Becker nevus syndrome developmental defect during embryogenesis hereditary skin disorder