Variability in the Michelin tire syndrome. A child with multiple anomalies, smooth muscle hamartoma, and familial paracentric inversion of chromosome 7q.

We describe a 2 1/2-year-old boy who has hirsutism and ringed creases of the extremities associated with an underlying smooth muscle hamartoma. Cutaneous findings in this child resemble those in other reports of the "Michelin tire syndrome." Histologic examination showed numerous well-demarcated fascicles of smooth muscle cells randomly distributed at all levels of the reticular dermis with haphazard orientation. These cells were immunoreactive with desmin, which confirmed their smooth muscle nature. In addition to the skin changes, this child has multiple unusual phenotypic anomalies, some of which have not previously been associated with the Michelin tire syndrome. These include distinctive facial dysmorphia, submucous cleft palate, lateral clefting of the mouth, genital, and dental anomalies. He also developed seizures at age 2 1/2 years and has moderate developmental delay. The patient and his mother have apparently identical paracentric inversions of the long arm of chromosome 7 (46,XY,inv(7)(q22q31.3) with no detectable loss or gain of either chromosomal material or DNA markers from the cystic fibrosis (CFTR) region. The relevance, if any, of the karyotypic abnormality to the phenotype in this child is discussed.