Systemic paediatrics: thrombocytopenia with absent radii: practice question

A Pediatrics question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Pediatrics · Systemic paediatrics: thrombocytopenia with absent radii

Sample item

A newborn has platelets of 20,000 per microlitre, bilateral absent radii and well-formed thumbs. Which diagnosis is most likely?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

A. TAR syndrome

In thrombocytopenia with absent radii (TAR) syndrome the radii are absent bilaterally but the thumbs are present, and thrombocytopenia is worst in infancy and improves with age. In Fanconi anaemia the radius and thumb are hypoplastic or absent, and marrow failure develops later in childhood. TAR is autosomal recessive.

Option by option

  • A. TAR syndrome (correct)

    Correct. Absent radii with present thumbs and neonatal thrombocytopenia define TAR syndrome.

  • B. Diamond-Blackfan anaemia

    Diamond-Blackfan anaemia causes red cell aplasia, not thrombocytopenia.

  • C. Holt-Oram syndrome

    Holt-Oram syndrome has upper limb defects with congenital heart disease but normal platelets.

  • D. Fanconi anaemia

    Fanconi anaemia usually has thumb abnormalities and progressive pancytopenia after infancy.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Pediatrics question

What is the answer to this Pediatrics question?

The best answer is A, TAR syndrome. In thrombocytopenia with absent radii (TAR) syndrome the radii are absent bilaterally but the thumbs are present, and thrombocytopenia is worst in infancy and improves with age.

Why is "Diamond-Blackfan anaemia" not the answer?

Diamond-Blackfan anaemia causes red cell aplasia, not thrombocytopenia.

Why is "Holt-Oram syndrome" not the answer?

Holt-Oram syndrome has upper limb defects with congenital heart disease but normal platelets.

Why is "Fanconi anaemia" not the answer?

Fanconi anaemia usually has thumb abnormalities and progressive pancytopenia after infancy.

What concept does this question test?

It tests Systemic paediatrics: thrombocytopenia with absent radii in Pediatrics. In Fanconi anaemia the radius and thumb are hypoplastic or absent, and marrow failure develops later in childhood. TAR is autosomal recessive.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Systemic paediatrics: thrombocytopenia with absent radii?

Memorise milestones and the vaccine schedule as tables and revise them often. Then use the flashcards and the other Pediatrics questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.