Rheumatoid Arthritis (RA): Subcutaneous nodules are a common extra-articular manifestation of RA, often found on the extremities and trunk. They are usually associated with more severe disease and can be a sign of active inflammation.

Gout: Tophi, which are deposits of monosodium urate crystals, can form subcutaneous nodules, typically on the extremities, in patients with chronic gout.
Sarcoidosis: This systemic granulomatous disease can cause subcutaneous nodules as part of its skin manifestations, which can appear on the trunk and extremities.
Lipoma: Benign tumors composed of fat tissue, lipomas can present as subcutaneous nodules anywhere on the body, including the extremities and trunk.

Neurofibromatosis Type 1 (NF1): While less common, NF1 can present with subcutaneous neurofibromas, which are a type of tumor that arises from nerve tissue. Missing this diagnosis could have significant implications for the patient and their family due to the genetic nature of the disease.
Subcutaneous Panniculitis-like T-cell Lymphoma (SPTCL): A rare and aggressive form of lymphoma that presents with subcutaneous nodules, often on the legs. Early diagnosis is crucial for treatment and prognosis.

Erythema Induratum (Bazin Disease): A rare form of panniculitis that presents with recurrent subcutaneous nodules, typically on the calves of young women. It is often associated with tuberculosis.
Nodular Vasculitis: Also known as erythema induratum, this condition involves inflammation of the blood vessels and can present with subcutaneous nodules, usually on the lower legs.
Subcutaneous Granuloma Annulare: A benign condition characterized by the formation of granulomas in the subcutaneous tissue, presenting as nodules, often on the extremities or trunk.