Acral persistent papular mucinosis: a rare child case report and literature review.

Background: Acral persistent papular mucinosis (APPM) is a rare idiopathic subtype of localized lichen myxedematosus. To date, there have been less than 41 APPM cases reported worldwide, however, almost all patients were older than 18 years of age. A 7-year-old child was first reported in this paper. Case Description: A 7-year-old boy was admitted to our hospital with a solitary skin-colored papule on the radial side of the middle segment of his right index finger. The patient wanted to know the exact diagnosis and remove it because the flexion movement of the middle segment had been affected. Thus, a surgery was performed. Histopathological examination of a biopsy specimen obtained from the papule on the radial side of the middle segment of his right index finger showed a focal and well-circumscribed deposit of mucin in the papillary and middermis. The deposit never extended deeply into the reticular dermis. Mucin spared a subepidermal area in the papillary dermis. Alcian blue stains can highlight the mucin. The papule was histologically diagnosed as an APPM and excised surgically. The wound gradually healed after the operation, and no obvious recurrence, scar or other discomfort was observed during follow-up so far. Conclusions: To the best of our knowledge, this is the rare case of a child APPM presenting as a solitary papule affecting the flexion movement of the middle segment. Since it is a rare disease, we report this case to contribute to future research on the diagnosis and pathogenesis of APPM.