Ataxia telangiectasia is characterised by all of the following except –
**Core Concept**
Ataxia telangiectasia (AT) is a rare, autosomal recessive disorder characterized by progressive cerebellar ataxia, telangiectasias, and immunodeficiency. It is caused by mutations in the ATM gene, which plays a crucial role in the repair of DNA double-strand breaks.
**Why the Correct Answer is Right**
The correct answer is associated with the pathophysiology of AT, which involves the disruption of the ATM kinase function. This leads to impaired activation of checkpoint kinases, such as Chk2, and subsequent accumulation of DNA damage, particularly in lymphoid cells. As a result, AT patients are prone to lymphomas and other malignancies. The correct answer is also linked to the clinical manifestations of AT, including progressive ataxia, telangiectasias, and immunodeficiency.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because AT is not primarily characterized by peripheral neuropathy. While some patients may exhibit peripheral neuropathy, it is not a hallmark feature of the disorder.
**Option B:** This option is incorrect because AT is associated with telangiectasias, which are dilated blood vessels that appear as red spots on the skin and mucous membranes. However, telangiectasias are not a distinguishing feature of other diseases listed in this option.
**Option C:** This option is incorrect because AT is characterized by a distinct clinical triad of progressive cerebellar ataxia, telangiectasias, and immunodeficiency. While some patients may exhibit cognitive impairment, it is not a primary feature of the disorder.
**Clinical Pearl / High-Yield Fact**
Ataxia telangiectasia is a rare disorder characterized by a distinct clinical triad, and it is essential to consider this diagnosis in patients with progressive ataxia, telangiectasias, and immunodeficiency.
**Correct Answer: D.**