Medical Laboratory Genetics Hub

🧬 Clinical vignettes to sharpen your medical genetic diagnostic skills - great for exam prep (such as ABMGG, ABGC) and continuing certification. 🩺

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The finding of a cherry red spot on the macula is a classic clinical sign associated with Tay-Sachs and other similar storage disorders. The family history of a similarly affected cousin supports a genetic disorder with a recessive inheritance pattern. 5/

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PATIENT VIGNETTE: Parents are concerned about their 8-month-old infant who, they report, was developing normally until 6 months of age when they noticed he began to startle easily to sounds. 1/

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This accumulation disrupts normal cellular function and manifests as a loss of motor skills, hypotonia, and neurological deterioration, which are symptoms described in the vignette. 4/

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This hereditary pattern is consistent with autosomal dominant inheritance seen in HNPP Environmental factors or sporadic conditions are less likely given the familial recurrence and characteristic clinical findings. 3/

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PATIENT VIGNETTE: A 32-year-old woman presents to the clinic with a history of recurrent numbness and weakness in her hands and feet that seems to occur after repetitive tasks or sustained positions. She mentions that she recently developed foot drop after a long hike. 1/

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pattern consistent with the patient's suspected diagnosis' is correct because it acknowledges the likelihood of a familial form of neuropathy, where the similar presentation in a direct relative (the father) implicates inheritance as a factor in the patient’s clinical picture. 2/

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🧬 NEW VIGNETTE QUESTION 🧬

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QUESTION: If the suspected diagnosis is confirmed confirmed, what is the pathophysiologic mechanism of the disease in this patient?

A. Dystrophin deficiency leading to muscle degeneration
B. Accumulation of glucocerebroside in lysosomes
C. 1/

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cases; gain of methylation at ICR1 on the maternal chromosome - approximately 5% of cases; paternal UPD(11) - approximately 20% of cases; loss of methylation at ICR2 on the maternal chromosome - approximately 50% of cases. 3/

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PATIENT VIGNETTE: A 6-month-old infant girl is brought to the pediatric clinic due to her parents' concerns about her rapidly increasing size compared to her older brother at the same age. 1/

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BWS is caused by a variety of molecular mechanisms involving a complex imprinted region at 11p15.5. Each answer choice represents a known molecular cause of BWS, accounting for the following proportion of cases (per GeneReviews): Maternal CDKN1C mutation - approximately 5% of 2/

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🧬 NEW VIGNETTE QUESTION 🧬

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QUESTION: The father's history of 'bad ankles' and 'clumsy hands' may be indicative of:

A. Unrelated somatic mutations
B. A sporadic neurological condition
C. An inherited pattern consistent with the patient's suspected diagnosis
D. 1/

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A muscle biopsy would not be informative in diagnosing PMP22-related disorders; a nerve biopsies were previously employed in cases of suspected PMP22-associated neuropathies, but are now less common, as less invasive molecular testing can readily confirm these diagnoses. 5/

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variants resulting in loss-of-function of PMP22, which are causative for HNPP in some cases; however, since the recurrent deletion is found in up to 90% of HNPP patients, a methodology that tests for deletions is more likely to confirm this suspected diagnosis. 4/