Beyond the Skin: Nail Clues to a Bone Disease.

Chronic recurrent multifocal osteomyelitis (CRMO) is a rare autoinflammatory bone disorder that predominantly affects children, and approximately 25% patients also present with an associated inflammatory condition. Most patients respond to nonsteroidal anti-inflammatory drugs, but refractory cases may need corticosteroids, bisphosphonate therapy, or disease-modifying antirheumatic drugs (DMARDs) like methotrexate, sulfasalazine, tumor necrosis factor-alpha (TNF-α) inhibitors, or even anti-interleukin-1 (anti-IL-1) blockers. We report the case of a previously healthy nine-year-old girl presenting with a four-week history of right hip pain and limping, associated with recent swelling and pain over the left sternoclavicular joint. There was no fever or systemic symptoms. Laboratory tests showed elevated inflammatory markers, with negative antinuclear antibody and HLA-B27. Multifocal inflammatory bone lesions involving the right femoral neck, left clavicle, left proximal tibia, and right pubic symphysis were identified on imaging, consistent with CRMO. Bone biopsy excluded malignancy. Physical examination showed dystrophic changes in all fingernails, with a history of nail pitting for one year, leading to the diagnosis of CRMO associated with psoriasis. Treatment with naproxen, topical calcitriol, and methotrexate resulted in complete clinical remission and resolution of nail dystrophy within eighteen months. This case highlights the importance of recognizing CRMO as part of the psoriatic disease spectrum in children presenting with multifocal bone pain and nail changes. As reported in the literature, CRMO is often associated with other inflammatory disorders, such as psoriasis, with an estimated prevalence of around 4%. Moreover, a thorough physical examination was essential in this case, allowing the identification of trachyonychia or twenty-nail dystrophy, a potential manifestation of conditions such as alopecia areata, lichen planus, or psoriasis, which may precede cutaneous lesions and, in 1-5% of patients, may be the only manifestation of the disease, making its diagnosis particularly challenging.