Systemic Lupus Erythematosus

Anti-dsDNA antibodies are highly specific (100%) for diagnosis of SLE. Its level correlates with lupus activity.

Explanation: Malar rash in SLE: Fixed erythema, flat or raised, sparing the nasolabial folds

Stem Breakdown:

Fever, arthritis, and a malar rash: These are classic symptoms of systemic lupus erythematosus (SLE), an autoimmune disease that can affect multiple organs.
Positive ANA and anti-dsDNA antibodies: These antibodies are highly specific for SLE, especially anti-dsDNA, which correlates with disease activity.
Option Analysis:

A) Rheumatoid arthritis: Rheumatoid arthritis primarily causes symmetric polyarthritis, particularly affecting the small joints of the hands and feet. It is not typically associated with a malar rash or positive anti-dsDNA antibodies.
B) Systemic lupus erythematosus (SLE): This is the correct diagnosis. Davidson and Harrison both emphasise that SLE is a systemic autoimmune disease characterised by a wide range of clinical features, including the malar (butterfly) rash, arthritis, renal involvement, and positive ANA and anti-dsDNA antibodies.
C) Dermatomyositis: Dermatomyositis is an inflammatory myopathy that causes muscle weakness and characteristic skin findings (e.g., heliotrope rash, Gottron’s papules), but it does not cause the malar rash or positive anti-dsDNA antibodies seen in SLE.
D) Sjögren’s syndrome: Sjögren’s syndrome is characterised by dry eyes and dry mouth due to autoimmune destruction of the salivary and lacrimal glands. It does not typically present with a malar rash or positive anti-dsDNA antibodies.

Ref: Davidson 23rd; P-992 , box : 24.10

Targets for antiphospholipid antibodies
 β2 -glycoprotein 1
 Protein C  Annexin V  Prothrombin (may result in haemorrhagic presentation)

Infections are the leading cause of death in patients with systemic lupus erythematosus (SLE), as noted by Davidson. The immunosuppressive therapies used to control lupus, such as corticosteroids and cytotoxic drugs, increase the risk of severe infections. Harrison adds that while renal failure was once a leading cause of mortality in SLE, advances in treatment have improved long-term outcomes, with cardiovascular complications and infections now being more common causes of death.

Answer: A
Explanation: The "butterfly" or malar rash is a hallmark feature of systemic lupus erythematosus (SLE), described in both Davidson and Harrison. This rash typically spares the nasolabial folds and is often triggered by sun exposure. SLE is a multisystem autoimmune disease, and skin manifestations like the malar rash are part of the diagnostic criteria.