Rheumatoid Arthritis (RA): This is a common condition that often presents with symmetric hand stiffness, particularly in the morning, and can lead to deformities if not treated. The stiffness in RA is typically worse after periods of inactivity.

Osteoarthritis (OA): OA can cause hand stiffness, especially in the proximal interphalangeal and distal interphalangeal joints, and is often associated with bony enlargements and pain.
Tendinitis or Tenosynovitis: Inflammation of the tendons or their surrounding sheaths can cause stiffness, especially with specific movements or activities.
Dupuytren's Contracture: A condition characterized by thickening of the palmar fascia, leading to stiffness and eventual contracture of the fingers.

Ganglion Cysts: While not typically life-threatening, ganglion cysts can cause significant discomfort and stiffness, especially if they compress nerves.
Infections (e.g., Septic Arthritis): Infections within the hand or wrist can cause severe stiffness, pain, and swelling, and require urgent medical attention to prevent serious complications.
Neoplastic Conditions: Tumors, whether benign or malignant, can cause stiffness and other symptoms, and early diagnosis is crucial for effective treatment.

Scleroderma: A chronic autoimmune disease that can cause skin thickening and stiffness in the hands, among other symptoms.
Ehlers-Danlos Syndrome: A group of genetic disorders affecting connective tissue, which can lead to joint hypermobility and stiffness.
Psoriatic Arthritis: An inflammatory condition associated with psoriasis, which can cause hand stiffness, swelling, and pain, often accompanied by skin and nail changes.