11. A newborn presents with craniofacial abnormalities, severely reduced muscle tone, and seizures. Biochemical analysis reveals elevated very long chain fatty acids in serum. What is the most likely underlying cause?

1. A

   A. Mitochondrial inheritance

2. B

   B. Lysosomal storage disorder

3. C

   C. Peroxisomal biogenesis defect

4. D

   D. Simultaneously activate multiple tumor suppressor genes

Appeared in: INI-CET EXAM -2026

Explanation

• The defining clinical clue is the elevated level of very-long-chain fatty acids (VLCFAs) in the serum.
• Peroxisomes are the specific cellular organelles responsible for the beta-oxidation (breakdown) of VLCFAs.
• A defect in the formation (biogenesis) of peroxisomes leads to a failure of this metabolic process, causing toxic accumulation of VLCFAs.
• This accumulation disrupts normal development and function of the brain, liver, and kidneys, resulting in the constellation of symptoms described: craniofacial abnormalities, severe hypotonia, and seizures.
• This clinical picture is classic for Zellweger syndrome spectrum disorders, which are the most severe form of peroxisomal biogenesis defects.

Why Other Options Were Wrong

• Option A: Disorders of mitochondrial inheritance primarily disrupt cellular energy (ATP) production. While they can cause neurological symptoms like seizures and hypotonia, their hallmark biochemical finding is often lactic acidosis, not elevated VLCFAs.
• Option B: Lysosomal storage disorders result from defects in lysosomal enzymes, leading to the accumulation of other substrates like mucopolysaccharides or sphingolipids. They do not cause an accumulation of VLCFAs.
• Option D: This describes a mechanism related to cancer biology (oncogenesis), where the loss of control over cell growth leads to tumors. It is completely unrelated to a congenital metabolic disorder presenting in a newborn.

Related Visual

Clinical Relevance

• Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Inborn errors of metabolism, specifically peroxisomal disorders as background academic context rather than a clinical decision trigger.
• Early recognition of inborn errors of metabolism is critical. The symptoms in this question (hypotonia, seizures) are non-specific, but the combination with dysmorphic features should prompt a metabolic workup.
• Nurses play a key role in observing for these signs in the neonatal intensive care unit (NICU), ensuring that appropriate biochemical tests are collected, and providing supportive care.
• For families with an affected child, genetic counseling is essential to discuss the autosomal recessive inheritance pattern and the risk of recurrence in future pregnancies (25%).

How to Approach the Question

• First, analyze the patient's clinical presentation: a newborn with a cluster of severe symptoms including craniofacial abnormalities, poor muscle tone, and seizures.
• Next, identify the most specific and objective piece of data provided. In this case, it is the biochemical analysis showing 'elevated very long chain fatty acids (VLCFAs)'. This is the crucial diagnostic clue.
• Systematically evaluate each option by linking it to the key finding. Ask yourself, 'Which of these defects would cause VLCFAs to accumulate?'
• Recall or deduce the function of each cellular component. Peroxisomes are responsible for VLCFA metabolism. Therefore, a defect in peroxisomes (Option C) directly explains the lab result.
• Eliminate the other options. Mitochondrial defects affect energy (ATP) and cause lactic acidosis. Lysosomal defects involve other substrates. Tumor suppressor genes are related to cancer.
• Conclude that the peroxisomal biogenesis defect is the only option that cohesively explains the entire clinical and biochemical picture.

Concept Tested & Keywords

• Concept Tested: Inborn errors of metabolism, specifically peroxisomal disorders.
• Stem keywords: newborn, craniofacial abnormalities, reduced muscle tone, seizures, elevated very long chain fatty acids
• Lead-in keywords: most likely underlying cause
• Clinical cues: The combination of severe neurological symptoms in a newborn with the specific lab finding of elevated very long chain fatty acids (VLCFAs) is the key to the diagnosis.

Question ID

QxZeXCyuuXg2c_Pce9JPZu

Copy ID

Reference Book

E6 Pathology- ROBBINS & COTRAN PATHOLOGIC BASIS OF DISEASE 10TH Ed p. 1288-1290

E6 Nelson Textbook of Pediatrics(2024) — Volume 2 p. 232-234

E6 Medicine Harrison 22e Part 2 p. 1695-1697