MedGen

Mitochondrial complex IV deficiency nuclear type 16 (MC4DN16) is an autosomal recessive metabolic disorder with highly variable manifestations. Common features include failure to thrive with poor overall growth, short stature, and microcephaly. Some patients additionally have neurologic involvement, including developmental regression with severe hypotonia, feeding difficulties, and seizures. Brain imaging in the more severely affected patients shows cerebral and cerebellar atrophy and abnormal lesions in the basal ganglia. In all cases, patient tissues show variably decreased levels and activity of mitochondrial respiratory complex IV (summary by Pillai et al., 2019). For a discussion of genetic heterogeneity of mitochondrial complex IV (cytochrome c oxidase) deficiency, see 220110. [from OMIM]

This syndrome has characteristics of triphalangeal thumbs and brachydactyly of the hands. Ectrodactyly of the feet and, more rarely, ectrodactyly of the hands were also reported in some family members. Transmission is autosomal dominant. [from SNOMEDCT_US]

Underdevelopment (hypoplasia) of the third toe. [from HPO]