Insights Gained From an Ultrarare Case of Progressive Osseous Heteroplasia With Severe Complications.

Progressive osseous heteroplasia (POH) is an exceptionally rare genetic disorder characterized by progressive heterotopic ossification of cutaneous, subcutaneous, and deep connective tissues. Most cases are associated with paternally inherited inactivating mutations in the guanine nucleotide-binding protein, alpha-stimulating gene. However, the genetic basis remains undefined in a subset of patients, adding further complexity to its pathogenesis. With fewer than 100 documented cases worldwide, POH presents significant diagnostic and therapeutic challenges, compounded by its rarity and clinical heterogeneity. Typically manifesting in infancy with dermal ossification, the disorder progresses to involve deeper structures, leading to ankylosis, deformities, and profound functional limitations. Unlike other ossification disorders, such as fibrodysplasia ossificans progressiva and Albright's hereditary osteodystrophy, POH is characterized by intramembranous ossification and a distinct lack of skeletal malformations. We report the case of an adult male with unilateral POH, a particularly unusual presentation, further complicated by septic arthritis, progressing to shock and multiorgan dysfunction. The patient initially presented with severe hip pain and functional impairment. Imaging confirmed septic arthritis, and conservative management with medical therapy and long-term antibiotics was initiated. Despite these measures, his condition deteriorated, culminating in septic shock and organ failure. The absence of established guidelines for POH necessitated careful interdisciplinary deliberation. Surgical intervention, including debridement, proximal femoral osteotomy, and placement of an antibiotic-impregnated spacer, was performed. A second-stage total hip arthroplasty restored mobility and resolved systemic complications, resulting in significant functional recovery. This case underscores the significant challenges posed by ultra-rare diseases like POH, where clinical management is often hindered by the absence of evidence-based protocols or precedent. The reliance on individualized decision-making highlights the importance of careful documentation and reporting of such cases to guide future clinical practice. Furthermore, the complexity and unpredictability of POH underscore the need for collaborative research efforts aimed at developing robust diagnostic criteria, therapeutic strategies, and long-term management guidelines for this debilitating condition.