The Diligent Lego Player with Talocalcaneal Callosities

A 7-year-old boy presented for his annual healthy visit. His mother drew attention to the child's left foot, where she had noticed a swelling for several months. The boy had neither pain nor discomfort. The mother stated that there was no pressure from new or uncomfortable shoes. The boy was without complaints and in otherwise excellent general condition on physical examination. The two non-tender lumps on the left lateral dorsal foot (Figure 1) were sized approximately 2 cm, had firm-elastic consistency on palpation, and were covered by rough, hyperpigmented skin. These lesions became more prominent during adduction and plantar flexion of the foot. Passive and active ankle mobility was unrestricted, with no signs of ligament or tendon instability. His gait was unremarkable, with the ability to walk on heels and toes. Ultasonography of the lesions (Figure 2) revealed only a diffuse thickening of the cutis in the lateral ankle area, with mixed echogenicity. The lesion did not extend to deeper tissues, had no connection to the joint space, and showed no bone destruction. Targeted history revealed that the boy was used to playing on the floor with his left foot flexed under his buttocks (Figure 3). The mother was advised to discourage this sitting position and adopted a watchful waiting approach. The boy no longer played for hours in this posture, and the callosities on the dorsal foot gradually faded.Figure 3Typical seating posture while playing on the floorView Large Image Figure ViewerDownload Hi-res image Download (PPT) Although talocalcaneal callosities should be a straightforward clinical diagnosis, they are often misinterpreted as other entities with similar appearances (eg, ganglion, exostosis, benign soft-tissue tumors). While the lumps had an appearance and location suggestive of exostosis or ganglion, a key finding, giving a hint toward the correct diagnosis, was the rough, hyperpigmented skin. This phenomenon typically occurs in children who spend hours sitting barefoot on the floor with their feet flexed under their buttocks, playing with Lego bricks or other toys. For this reason, Swiss orthopedist Hanspeter Huber coined the playful term "Lego player foot." (1Huber H. Der Lego-Spieler-Fuss.Swiss Medical Forum. 2014; 14: 915-916Google Scholar) The excessive keratinization results from pressure or rubbing at the exposed areas. The main pressure points are located above the talus head and anterior calcaneus process. Talar callosities have been well described outside the pediatric literature among adults seen in strict prayers ("prayer callosities") and people practicing intensive yoga rituals. (2Fosse N. Rast A.C. KAmmerman A. Sonderegger J. NAvarini A. Goldust M. et al.Pitfall prayer marks: recognition and appropriate treatment: a case report and review of the literature.Dermatol Ther. 2020; 33e13176Crossref PubMed Scopus (2) Google Scholar,3Verma S.B. Wollina U. Callosities of cross legged sitting: "yoga sign"--an under-recognized cultural cutaneous presentation.Ind J Dermatol. 2008; 47: 1212-1214Crossref Scopus (17) Google Scholar) Considering its pathomechanism, talar callosity may be frequently encountered in pediatric practice. (1Huber H. Der Lego-Spieler-Fuss.Swiss Medical Forum. 2014; 14: 915-916Google Scholar, 4Verbov J.L. Monk C.J. Talar callosity- a little-recognized common entity.Clin Exp Dermatol. 1991; 16: 118-120Crossref PubMed Google Scholar) The diagnosis is typically made clinically. The callosities are best seen during adduction and plantarflexion of the foot. A hint toward the correct diagnosis is the hyperpigmented keratotic skin over the lump, which is usually missing in the case of ganglion, exostosis, or other benign soft-tissue lesions. Ultrasonography can be a diagnostic aid, and biopsy is generally not indicated. (5Luna-Bastante L. Lopez Negrete E. Alonso Naranjo L. Roustan G. Alfageme F. Sonography of a case series of talar callosities.J Ultrasound. 2022; 25: 983-987Crossref PubMed Scopus (1) Google Scholar) Treatment is usually unnecessary, as playing on the floor decreases with age, so the keratinized pressure points disappear. (1Huber H. Der Lego-Spieler-Fuss.Swiss Medical Forum. 2014; 14: 915-916Google Scholar, 4Verbov J.L. Monk C.J. Talar callosity- a little-recognized common entity.Clin Exp Dermatol. 1991; 16: 118-120Crossref PubMed Google Scholar) In rare cases of pain or noticeable foot deformity, especially if persisting after appropriate intervention, osteochondroma should be considered. (6Keser S. Bayar A. Osteochondroma of the talar neck: a rare cause of callosity of the foot dorsum.J Am Podiatr Med Assoc. 2005; 95: 295-297Crossref PubMed Google Scholar) Excessive skin keratinization, characteristic location, and targeted history are helpful hints toward the correct clinical diagnosis. We aim to draw attention to these harmless changes and spread knowledge, which could prevent numerous misdiagnoses, unnecessary interventions, and parental concerns. Martina Minkov: Writing – review & editing, Writing – original draft, Project administration, Methodology, Formal analysis, Data curation. Milen Minkov: Writing – review & editing, Writing – original draft, Validation, Supervision, Methodology, Data curation, Conceptualization. Karoly Lakatos: Writing – review & editing, Visualization, Methodology, Investigation. We sincerely thank the parents for providing the pictures and the permission for their use.