Osteoarthritis (OA): Although OA is more common in older adults, it can occur in younger individuals, especially if there's a history of trauma, repetitive strain, or a family history of OA. The involvement of two fingers, particularly into the knuckles, could suggest an early onset or a secondary form of OA.

Rheumatoid Arthritis (RA): This autoimmune disorder often presents with symmetric joint pain and swelling, commonly affecting the hands. The patient's age and the specific involvement of the fingers into the knuckles are consistent with early RA.
Psoriatic Arthritis (PsA): PsA can cause joint pain and swelling, often accompanied by psoriatic skin lesions. The distribution of joint involvement can be asymmetric and may include the distal interphalangeal joints, which could fit the patient's symptoms.
Gout: Although gout typically affects the base of the big toe, it can involve any joint. The acute onset of intense pain and swelling in a few joints could suggest gout, especially if there are risk factors such as diet, alcohol use, or family history.

Septic Arthritis: This is a medical emergency that requires prompt diagnosis and treatment. Bacterial infection of a joint can cause severe pain, swelling, and systemic symptoms like fever. Missing this diagnosis could lead to joint destruction and significant morbidity.
Lyme Arthritis: Caused by the bacterium Borrelia burgdorferi, Lyme disease can lead to arthritis, particularly in the knees but potentially in any joint. Early recognition is crucial for effective treatment and prevention of long-term sequelae.

Sarcoid Arthritis: Sarcoidosis is a systemic disease that can cause arthritis, among other manifestations. Joint involvement is less common than pulmonary or skin manifestations but should be considered in the differential diagnosis of unexplained joint pain and swelling.
Hemochromatosis: This genetic disorder leads to iron overload and can cause arthritis, particularly in the second and third metacarpophalangeal joints, due to iron deposition in the joints. It's a rare cause of arthritis but important to diagnose due to its systemic implications.
Relapsing Polychondritis: A rare autoimmune disorder that can cause cartilage inflammation, leading to joint pain and swelling, among other symptoms. It's an important consideration in patients with unexplained, recurrent joint symptoms.