Resolution of extensive Mongolian spots (dermal melanocytosis) in a patient with mucopolysaccharidosis type II undergoing enzyme replacement therapy with pabinafusp alfa: A case report

Abstract

Background

Mucopolysaccharidosis type II (MPS II; Hunter syndrome), an X-linked recessive lysosomal storage disease caused by a deficiency of iduronate-2-sulfatase, leads to systemic accumulations of glycosaminoglycans that affect multiple organs. It also has several distinctive cutaneous manifestations, in particular extensive Mongolian spots (dermal melanocytosis), which are often the earliest signs of the disease. The Mongolian spots in patients with MPS II are known to persist for much longer than they do in healthy children, and they are nonresponsive to hematopoietic stem cell transplantation or enzyme replacement therapy with idursulfase.

Case presentation

We report a case of extensive Mongolian spots extending upwards from the buttocks and on the abdomen in a Japanese boy who was diagnosed with neuronopathic MPS II at 15 months of age, whereupon treatment was started with weekly intravenous administration of pabinafusp alfa. After over 2 years of treatment, his neurocognitive development was maintained, and he showed no apparent somatic manifestations (e.g. hepatosplenomegaly, valvular dysfunctions or hearing loss), suggesting that pabinafusp alfa is effective in addressing both the neuronopathic and somatic symptoms of MPS II. Notably, the extensive Mongolian spots covering the patient's sacral and extrasacral regions resolved markedly in terms of both size and colour.

Discussion

This is the first report of improvements in MPS II-associated extensive Mongolian spots brought about by enzyme replacement therapy. Further study of MPS II-related skin lesions and their clinical course is required to elucidate the dermatological pathology of a disease that has hitherto been nonresponsive to conventional therapies.