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Postaxial polydactyl (vestigial digit) in a military patient

© Author(s) (or their employer(s)) 2022. No commercial reuse. See rights and permissions. Published by BMJ. A 28yearold service person presented to a Defence Primary Healthcare Centre with a ‘wart’ that they have had since childhood. The lesion was on the lateral aspect of the left hand (nondominant) little finger distal interphalangeal joint (Figure 1). The lesion had been treated as a wart previously and excised around 10 years ago at a civilian General Practice (GP). It is unclear what technique was used to remove the lesion. Since then it had completely regrown in the same location. The patient came in seeking removal as they had done previously due to it catching on items in their daily life. Moreover, it was having an occupational impact through interfering with their job role, which was manual in nature. There was no significant dermatological history and no other lesions of note. As shown in Figure 1, the lesion was conical with a smooth epithelial base and a keratinised tip. It was connected by soft tissue with no deeper bony or muscular attachment. The general organised morphology and lack of the typical papilliform structures expected of a wart led to the differential of a vestigial digit. This was supported by the history of regrowth, a characteristic of the regenerative properties seen on the fingertips. Further investigations such as an Xray were not felt to be of value in the primary care management. The patient was referred to a consultant in plastic surgery who agreed with the diagnosis made. Their plan will be to surgically remove the appendage in secondary care. Polydactyly encompasses a wide range of congenital presentations from distinct morphological digits to vestigial appendages and generally occurs in the upper limbs. Its aetiology lies in the failure of the biochemical signalling pathways during embryological development. The most influential of these is the Sonic Hedgehog protein which acts down a concentration gradient to influence digit differentiation along with bone morphogenic proteins. 3 Polydactyly can present as an isolated issue or as part of a wider syndrome or disease pattern such as DiamondBlackfan and Fanconi anaemias, Ellisvan Creveld syndrome, the VACTERL (Vertebral defects, Anal atresia, Cardiac defects, Tracheoesophageal fistula, Renal anomalies and Limb abnormalities) association, trisomy 13 and trisomy 21. It can be picked up during routine foetal ultrasound or noticed in the first few weeks of life. As polydactyly highlights a failure of normal embryological development, it can serve as a sentinel indicator for further clinical investigation such as through ultrasound studies of the major body systems or genetic testing. The literature places the incidence at between 1.5 and 10.7 live births with men being up to twice as likely to be affected compared with women. Black populations have a higher incidence at 1 in 300, while white populations are around 1 in 3000. Though initially presenting with what had previously been treated as a wart, consideration of the history and morphology of the lesion led to the rare diagnosis of a postaxial digit in an adult. Medical officers are exposed to a large and varied population outside of medical centres through various tasks such as exercises, entry medicals and operations. Therefore, uncommon presentations are seen more readily due to the numbers involved. With the previous diagnosis of a wart and the occupational impact on the patient, this case highlights the benefits of considering differential diagnoses even with seemingly simple cases.