Bilateral, Asymmetric Proximal Focal Femoral Deficiency – A Rare Presentation

Bilateral asymmetric proximal femoral focal deficiency (PFFD) is an exceptionally rare condition where both femurs are affected to different degrees, clinically presenting with disproportionate extremity length discrepancy and potentially with other related musculoskeletal abnormalities. While bilateral presentation is uncommon, marked intra-individual asymmetry bridging the polar extremes of the classification spectrum is exceptionally rare. Managing these cases is uniquely challenging, requiring highly customized, independent strategies for each limb to achieve early independent ambulation and acceptable cosmesis. We report a case of a 5-year-old male presenting with bilateral, highly asymmetric PFFD (Aitken Class A on the right and Class D on the left). The case study presented here warrants documentation not only due to the inherent rarity but also to underscore the diagnostic pitfalls encountered in clinical practice. Unawareness of this rare pathology can lead to clinical and radiological diagnostic failure on the less severely affected side, compromising subsequent management. Ultimately, this case serves as a crucial reminder of the need for systematic bilateral evaluation in all suspected cases of lower extremity dysgenesis. Continuous, long-term follow-up remains essential to manage evolving complications and adapt interventions to the growing child. We also reviewed the potential embryological mechanisms underlying such severe phenotypic divergence within a single patient.