Johnson-McMillin syndrome, a neuroectodermal syndrome with conductive hearing loss and microtia: report of a new case

In 1983, Johnson et al. described 16 related individuals with alopecia, anosmia or hyposmia, conductive hearing loss, microtia and/or atresia of the external auditory canal, and hypogonadotrophic hypogonadism inherited in an autosomal dominant pattern. Other less constant manifestations included facial asymmetry, mental retardation, congenital heart defect, cleft palate, and choanal stenosis. An isolated case was reported later (Johnston et al. [1987: Am J Med Genet 26: 925-927]) and thereafter an affected mother and son (Hennekam and Holtus [1993: Am J Med Genet 47: 714-716]). We describe an additional unrelated female patient with features resembling those of the previously reported cases. She presented with intrauterine growth deficiency, microcephaly, alopecia, bilateral microtia with canal atresia, conductive hearing loss, partial left facial palsy, posterior cleft palate, left choanal stenosis, tetralogy of Fallot, developmental delay, and right thumb polydactyly. Because the phenotypic abnormalities in this syndrome affect the brain, facial structures, ectoderm and its derivatives, outflow tract of the heart, and Rathke's pouch derivatives, this has suggested to previous authors etiologic involvement of the ectoderm and neuroectoderm of the first and second branchial arches, Rathke's pouch, and the diencephalon. Microtia with conductive hearing loss differentiates the condition from other ectodermal dysplasias. In the initial report, females appeared somewhat less affected than males, and there was male-to-male transmission. The mother of our patient manifests subtle features, which suggest she may be a mildly affected female. Additionally, there is a family history of early-onset alopecia in the maternal grandfather's relatives.