**Question:** Which among the following is seen in antiphospholipid antibodies syndrome?

A. Thrombocytopenia
B. Atypical hemolytic uremic syndrome (aHUS)
C. Proteinuria
D. Skin rash

**Core Concept:** Antiphospholipid antibodies syndrome (APS) is an autoimmune disorder characterized by the production of antiphospholipid antibodies (aPL), which bind to phospholipids and proteins, leading to hypercoagulability and increased risk of thrombosis and recurrent pregnancy loss.

**Why the Correct Answer is Right:** Thrombocytopenia (decreased platelet count) is a common manifestation of antiphospholipid antibodies syndrome. APS can lead to microvascular thrombosis, affecting various organs and systems, resulting in thrombocytopenia.

**Why Each Wrong Option is Incorrect:**

B. Atypical hemolytic uremic syndrome (aHUS) is a thrombotic microangiopathy characterized by hemolytic anemia, thrombocytopenia, and acute kidney injury. While APS can share some clinical features with aHUS, it is not a correct answer as it is unrelated to antiphospholipid antibodies.

C. Proteinuria is a renal manifestation typically seen in conditions like lupus nephritis rather than APS. APS primarily causes thrombosis and thrombocytopenia.

D. Skin rash is not a specific feature of antiphospholipid antibodies syndrome and can be seen in various other autoimmune disorders and infections.

**Clinical Pearl:** Antiphospholipid antibodies syndrome is a clinical diagnosis requiring the presence of antiphospholipid antibodies and at least one clinical criterion (e.g., thrombosis, pregnancy loss). It is essential to consider APS when evaluating patients with thrombosis, recurrent pregnancy loss, or thrombocytopenia, especially in the context of a positive antiphospholipid antibody test (lupus anticoagulant, anticardiolipin antibodies, anti-beta-2 glycoprotein-1 antibodies).

**Correct Answer Explanation:** Antiphospholipid antibodies syndrome is a clinical diagnosis based on the presence of antiphospholipid antibodies and at least one clinical criterion (e.g., thrombosis, pregnancy loss, thrombocytopenia).

*Core Concept:* Antiphospholipid antibodies syndrome is a clinical diagnosis requiring the presence of antiphospholipid antibodies and at least one clinical criterion (e.g., thrombosis, pregnancy loss, thrombocytopenia). In this case, thrombocytopenia is a correct answer, as it is a common manifestation of antiphospholipid antibodies syndrome.

*Why the Wrong Options Are Incorrect:*

1. Proteinuria (Option C) is a renal manifestation typically observed in lupus nephritis. It is not a typical feature of antiphospholipid antibodies syndrome.
2. Skin rash (Option D) is not a specific feature of antiphospholipid antibodies syndrome and can be seen in various autoimmune disorders and infections.

*Clinical Pearl:* Antiphospholipid antibodies syndrome is a clinical