Sclerosteosis (craniotubular hyperostosis-syndactyly) with complex hyperphalangy of the index finger

We report a 4-year-old boy with sclerosteosis associated with severe digital dysostosis. The initial medical consultation was prompted by bilateral, asymmetrical syndactyly of the index and middle fingers. The left index finger had complicated phalangeal anomalies: hyperphalangy (supernumerary phalanx distal to the middle phalanx) and hypoplasia with bracket epiphyses of the proximal and middle phalanges. Development of facial nerve palsy, hearing impairment and generalized osteosclerosis had occurred between 3 years and 4 years of age, with the subsequent identification of a homozygous SOST mutation. Bilateral second and third fingers syndactyly associated with abnormal patterning of the same fingers should be considered prodromal signs of sclerosteosis.