In the mid-1990s the classification of the most common Mendelian-inherited arthrogryposis syndromes was revised. Distal arthrogryposes (DAs) were classified into 10 hierarchically related disorders according to the proportion of features they shared with one another (DA1–DA10). Features shared among the DAs include a consistent pattern of distal joint (hands and feet) involvement, limited proximal joint involvement, autosomal dominant inheritance, variable expressivity. Most FSS cases are sporadic, but there are also evidences of autosomal-dominant transmission in FSS. An autosomal recessive or X-linked recessive pattern may be observed in cases in which the parent has non-penetrant somatic mosaicism or germ-like mosaicism.
Several DA syndromes can be caused by mutations in 4 genes that encode proteins of the troponin-tropomyosin complex of fast-twich myofibres (mutations in TPM2, TNN12, TNNT3, MYH8).
The most frequently seen clinical manifestation are: scoliosis, dental crowding, strabismus, severe respiratory infections, hearing loss, fractures, hernia, cryptorchidism, headaches, malignant hyperthermia, joint dislocations, severe vomiting, arthritis/joint pain. Children with Freeman-Sheldon syndrome are recognized by the characteristic face (“whistling mouth”), microcephaly and mental retardation have been observed in one third of patients.
The authors present a 11-month-old boy with the phenotype of Freeman-Sheldon syndrome.