Pseudoainhum in Erythrodermic Psoriasis

Dear Editor, Pseudoainhum is a rare congenital or acquired disorder, characterized by the development of a constricting fibrotic band most commonly on a finger or toe. It has been described in association with various dermatoses. We report a child with erythrodermic psoriasis presenting with pseudoainhum. An 11-year-old boy diagnosed with chronic plaque psoriasis for 2 years presented with erythroderma and pain over the digits for 2 weeks. On examination, he had generalized erythema with large scaly plaques all over the body and thickening of the palms and soles. Onychomadesis with increased curvature and erythronychia were present over all the fingernails. The left little finger had a fibrotic band of constriction over the distal interphalangeal joint with distal bulbous enlargement and crusting over the lateral nail fold [Figure 1a and b]. The peripheral arterial pulses in both hands were normal. The diagnosis of pseudoaihnum of the left little finger was made.Figure 1: (a) Dorsoulnar view of the hand showing a fibrotic constriction band at the distal interphalangeal joint of the little finger with distal bulbous enlargement and crusting over the lateral nail fold. (b) Palmar view of the hand showing a fibrotic constriction band at the distal interphalangeal joint of the little fingerRoutine investigations were within the normal limits. X-rays of hands and feet were normal. He was treated with methotrexate at a weekly dose of 7.5 mg, along with applying 12% topical salicylic acid to the fibrotic band, resulting in significant improvement within 2 weeks. Ainhum (dactylolysis spontanea) is a disease of middle-aged African males accustomed to going barefoot, characterized by the development of fibrotic constricting rings at the base of one or multiple toes, most commonly affecting the fifth toe due to excessive fibrous tissue response to mechanical or infectious injuries. Pseudoainhum constrictions clinically resemble ainhum and both can lead to autoamputation. It can be classified into three pathophysiological categories:[1] congenital constricting bands, often linked to the umbilical cord;[2] constriction due to external factors, such as hairs or threads, typically resulting from factitial cause; and[3] constricting bands that develop secondary to other diseases, which may be hereditary or nonhereditary.[1] Hereditary causes include conditions such as pachyonychia congenita and mutilating keratodermas. Other genodermatoses include lamellar ichthyosis, progressive symmetric erythrokeratoderma, epidermolysis bullosa, tuberous sclerosis, and erythropoietic porphyria. Nonhereditary causes include a range of conditions such as Raynaud’s disease, diabetes mellitus, linear scleroderma, systemic sclerosis, leprosy, tertiary syphilis, and syringomyelia. Psoriasis is rarely associated with pseudoainhum and there are very few case reports.[2–4] The proposed mechanism of pseudoainhum in psoriasis is due to chronic inflammation and the formation of constricting bands due to the thickened, scaly plaques characteristic of psoriasis. If untreated, these bands may lead to irreversible damage and amputation of digits. Treatment includes both medical and surgical management, along with appropriate care for any underlying conditions. Various medical modalities include topical and injectable corticosteroids, retinoids, salicylates, topical pimecrolimus, and low-dose narrow-band ultraviolet B therapy. Surgical management includes the release of constricting bands by excision or by Z-plasty.[5] This report documents a rare association between pseudoainhum and psoriasis and emphasizes the importance of early recognition and treatment of this condition. Declaration of consent The authors certify that they have obtained all appropriate consent forms, duly signed by the parent(s)/guardian(s) of the patient. In the form, the parent(s)/guardian(s) has/have given his/her/their consent for the images and other clinical information of their child to be reported in the journal. The parents understand that the names and initials of their child/children will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.