Heterogeneity in adducted thumbs sequence.

We report on a boy with adducted thumbs, microcephaly, swallowing difficulties, hypotonia, and severe mental retardation, but without craniostenosis or arthrogryposis. An MRI scan showed myelinization according to age and mild ventricular enlargement. A muscle biopsy documented irregular-shaped and swollen mitochondriae, but results of mitochondrial function tests were normal. The clinical findings were consistent with a developmental defect of the central nervous system. We include a brief review of the 9 reported cases with adducted thumbs sequence.