Something's "going around": Skin creases on a baby's limbs (Michelin tire baby syndrome, or congenital diffuse lipomatosis)
1. What is this baby's condition?
2. How should it be managed?
You are asked to evaluate a 4-month-old girl whose parents are concerned about several circular bands around her arms and legs that have been present since birth. The bands do not cause her discomfort or interfere with her movements, and her growth and development have otherwise been normal.
Prenatal care was routine and the mother's pregnancy was uncomplicated. No abnormalities had been noted on fetal ultrasonography. There is no family history of similar bands in adults or children.
Congenital diffuse lipomatosisalso known as Michelin tire baby syndrome (MTBS) because of its resemblance to the mascot of the French tire manufactureris characterized by multiple, symmetric, circumferential skin creases, or bands, on the forearms, lower legs, and often the neck that are present at birth.1 Since the original description by Ross in 1969, 20 cases of this hamartomatous disorder have been reported, demonstrating the variability of clinical and histologic findings.15 Subtle, spontaneously regressing cutaneous findings in some children, most of whom have no associated anomalies, indicates that the true incidence of MTBS may be much higher than what is suggested by the few cases that have been reported.
Cutaneous findings. Symmetric, ringed skin bands that exaggerate the normal skin creases are usually most prominent on the arms and legs. Palmar and plantar skin may also have excessive skin folds, however. The bands, which number between one and five on each limb, do not appear to cause discomfort or interfere with function. Hirsutism of the arms, legs, shoulders, and buttocks may be present. Although the scalp hair of patients usually remains normal, long, thick, curled eyelashes and brows are typical.2,3
Extracutaneous findings. Most affected children are otherwise normal, but MTBS has been associated with a number of minor and major congenital anomalies.15 Reported associated facial dysmorphisms include epicanthal folds, hypertelorism, a downward slant to the eyes, a flat nasal bridge, and low-set ears. Also common are cleft lip and palate, a high arched palate, dental hypoplasia, and micrognathia. Orthopedic defects may be present in the extremities and as pectus excavatum, and may require surgical repair. Developmental delay and seizure disorders have also been variably reported.
Cause and pathogenesis. The cause of MTBS is poorly understood. Ross's original case was associated with histologic changes typical of nevus lipomatosis cutaneous superficialis (NLCS), suggesting that this disorder might represent a diffuse form of this lipomatous hamartoma. Since then, however, cases both with and without NLCS have been described. Moreover, an underlying smooth muscle hamartoma and defects of elastic fibers have been found in many affected children.25
Unrelated cytogenetic defects have been discovered in two MTBS patients who had multiple anomalies.2 Familial cases with isolated cutaneous involvement and male-to-male transmission support an autosomal dominant inheritance. Consequently, MTBS may represent disparate genetic disorders, which have a common cutaneous phenotype.
Differential diagnosis. The soft bands of MTBS are easy to distinguish from congenital amniotic constriction bands, which are fibrotic and associated with asymmetric limb defects, limb amputations, and craniofacial anomalies. Ainhumthe constriction bands that involve any digit, but most commonly affect the digital-plantar fold of the fifth toeshould not be confused with the findings of MTBS because ainhum may, without surgical intervention, progress to amputation of the digit. Histologically, MTBS may be confused with NLCS, smooth muscle hamartoma, and Becker nevus, but the clinical findings of these disorders are distinctive.
Course. You can reassure parents that their child's skin folds are likely to diminish or disappear without treatment. All affected infants deserve careful evaluation, however, to exclude orthopedic or other extracutaneous anomalies that call for early intervention. Full examination failed to reveal associated anomalies in this patient. She continues to thrive.
The next installment of Pediatric Dermatology: What's your Dx? will appear in October 2003.
Additional images of related disorders can be found on Dr. Cohen's Web site at www.dermatlas.org .
1. Ross CM: Generalized folded skin with an underlying lipomatous nevus: "The Michelin tire baby." Arch Dermatol 1969;100:320
2. Schnur RE, Herzberg AJ, Spinner N, et al: Variability in the Michelin tire syndrome: A child with multiple anomalies, smooth muscle hamartoma, and familial paracentric inversion of chromosome 7q. J Am Acad Dermatol 1993;28:364
3. Schnur RE, Zackai EH: Circumferential ringed creases ("Michelin tire babies") with specific histologic findings and/or karyotype abnormalities: Clues to molecular pathogenesis? (Letter) Am J Med Genet 1997;69:221
4. Pivnick EK, Wilroy RS, Martens PR, et al: Hypertrichosis, pigmentary retinopathy, and facial anomalies: A new syndrome? Am J Med Genet 1996;62:386
5. Oku T, Iwasaki K, Fujita H: Folded skin with an underlying cutaneous smooth muscle hamartoma. Brit J Dermatol 1993;129:606
Pediatric dermatology: What's your Dx? Contemporary Pediatrics July 2003;20:30.