Background There is considerable racial variation in the occurrence of melanonychia striata. The prevalence of melanonychia striata in the Chinese population is not known. The purpose of this study was to investigate the prevalence and characteristics of melanonychia striata in a Chinese population of patients.
Methods Two thousand, four hundred and fifty-seven Chinese patients attending an Asian medical clinic were examined for the presence of melanonychia striata in a cross-sectional prevalence survey. The examinations were carried out as part of the routine medical care provided to these patients. Patients of mixed racial background were excluded. The fingernails and toenails of each patient were examined, and the presence or absence of melanonychia striata, the anatomic distribution of the lesion, and the age and sex of the patient were recorded.
Results Melanonychia striata was not detected in patients aged less than 20 years. The condition was present in 0.6% of patients aged between 20 and 29 years. Thereafter, the prevalence increased gradually to 1.7% in patients aged 50 years and over. There was a significant relationship between age and the presence of melanonychia striata (χ2 = 141, P < 0.01). There was no significant sex-related difference in the age-specific prevalence (P > 0.05). The thumbs were most frequently affected, followed by the index fingers (P < 0.001). The condition was bilateral in 40% of cases. None of the patients had involvement of more than two digits.
Conclusion Melanonychia striata is uncommon in Chinese individuals, especially in those aged under 20 years. The male to female ratio is approximately equal. The thumbs are most frequently affected and the condition is often bilateral.