Pseudoainhum in psoriasis.

Sir,

Pseudoainhum is a condition characterized by the development of an acquired constricting ring most commonly around a digit. It has been described in association with various dermatoses. We describe a patient presenting in association with psoriatic erythroderma.

A 27-year-old male presented with generalized erythema and scaling all over body for 1 month. He had started developing erythematous scaly plaques on trunk and limb 2 months back that later coalesced to involve the whole body. At presentation, he had generalized erythema over the body with fine silvery scales [Figure 1] and thickening of palms and soles. The nails were thickened and dystrophic with subungual hyperkeratosis.

Figure 1

Psoriatic lesions on abdomen

Investigations including a hemogram, liver and kidney function tests and serum electrolytes were normal. A chest X-ray and Ultrasonography (USG) abdomen were normal. A skin biopsy was taken and histopathology was consistent with psoriasis.

During the hospital stay, he developed pain and tenderness with swelling of distal phalanges of both hands involving multiple digits. Cutaneous examination revealed a fissure with a fibrotic band of constriction over distal interphalangeal joints [Figure 2]. The peripheral arterial pulses in both hands were normally palpable. He was started on antibiotics and a surgical release of fibrotic band was done under local anesthesia. He improved markedly over the next 2 weeks.

Figure 2

Constriction band around the finger

Discussion

Ainhum and pseudoainhum are characterized by the development of constricting bands around a digit or a limb that may lead to auto amputation. Ainhum is a disease of unknown etiology, common in middle aged African males accustomed to walking barefoot. Pseudoainhum occurs as a secondary event that leads to annular constriction of digits.[12] There are three main varieties of pseudoainhum:

Congenital bands caused by umbilical cord;[3]

Acquired constricting bands secondary to trauma, mechanical injury, infection and specific disease;

Factitial constriction by hair, threads and fiber, common in children and mentally retarded persons.

Diseases associated with pseudoainhum are divided into hereditary and nonhereditary groups. Hereditary causes include pachyonychia congenital and mutilating keratodermas like Mal de Meleda.[45] Nonhereditary disease includes vascular abnormalities (Raynauds disease, diabetes mellitus and linear scleroderma) systemic sclerosis, sensory changes (leprosy, tertiary syphilis and syringomyelia), ergot poisoning, spinal cord tumors, or scar formation (burn, frostbite and trauma). It is uncommonly reported with psoriasis.

Surgery is the mainstay of therapy with release of constricting bands by excision or by Z-plasty.[6] In late stage, amputation may be indicated. Impending amputation can sometime be aborted by oral retinoids.

There are three previous reports of pseudoainhum associated with psoriasis. The first case documents the acute development of psoriasis and pseudoainhum of the finger over a period of 1 week presenting with a constricting band around the middle phalanx of a single digit.[7] In the second case, multiple constriction bands over several digits developed over a period of several months in chronic psoriasis.[8] In both these reports the patient responded well with surgical excision of band and conservative treatment of psoriasis as is the case in our patient. In the third case, a 5-month-old girl of psoriasis with pseudoainhum was successfully treated with topical pimecrolimus and low-dose narrowband UVB phototherapy.[9]

Our report substantiates the association of psoriasis and pseudoainhum. Although it is a rare association, early diagnosis and intensive medical and surgical management may avoid progression and amputation of digits.