Natural history of extensive Mongolian spots in mucopolysaccharidosis type II (Hunter syndrome): a survey among 52 Japanese patients.

Background: Recent reports have shown a correlation between extensive Mongolian spots and mucopolysaccharidosis type II (Hunter syndrome). However, a statistical survey of the incidence and natural history of extensive Mongolian spots among the patients with Hunter syndrome is lacking.
Objectives: To determine the prevalence of extensive Mongolian spots, to determine the natural course of the spots according to age in Japanese patients with Hunter syndrome, and to compare them with the results obtained from the patients' brothers who did not have Hunter syndrome.
Patients/methods: Fifty-two males with Hunter syndrome aged 3 to 40 years were studied. Twenty-five patients were examined in two clinics to determine the existence and characteristics of the spots. We interviewed their families about the spots in their neonates and the natural course of the spots according to their ages. The same survey was done among another 27 patients using a mailed questionnaire to their families. As control, we investigated 21 brothers of the patients by a mailed questionnaire to their families.
Results: The extensive Mongolian spots are identified in almost all the infants with Hunter syndrome and disappear extremely later in their life. The lesions had a high incidence of deep-blue hyperpigmentation. Regardless of age, the overall incidence was 78%. All of the brothers who did not have Hunter syndrome had common-type Mongolian spots in neonates, which regressed during their childhood.
Conclusion: Our results confirm a strong correlation between extensive Mongolian spots and Hunter syndrome for the Japanese population. The presence of extensive Mongolian blue spots should alert the physician to the possibility of Hunter syndrome.