FISH Analysis - Charcot-Marie-Tooth Neuropathy Type 1A

Clinical Use

Use

FISH Analysis for Charcot-Marie-Tooth Neuropathy Type 1A (CMT1A) is a Fluorescence In Situ Hybridization test aimed at detecting duplications in the PMP22 gene. This duplicative genetic alteration is responsible for roughly 50% of CMT1A diagnoses. CMT1 refers to inherited neurological conditions primarily emerging in adolescence, leading to demyelinating peripheral neuropathy characterized by sensory loss and distal muscle atrophy. A regular screening via FISH will not identify other variants associated with CMT; hence, it's recommended to follow up with Chromosome Microarray Analysis for comprehensive diagnosis. Testing in minors for conditions like CMT1A is discouraged unless symptomatic and with a family history.

Special Instructions

Consideration for testing minors is advised against due to the late-onset nature of CMT1A. Testing is suggested for symptomatic individuals, particularly those with a family history of CMT. Sample collection must adhere strictly to specified guidelines, ensuring reliability and accuracy in results. Using the appropriate tube (Sodium Heparin) is critical; alternatives like lithium heparin are allowed but discouraged, while EDTA and plasma separator tubes are not acceptable for cytogenetic testing.

Limitations

The limitations of this FISH assay restrict it to identifying only duplications or deletions of the PMP22 gene without ruling out structural rearrangements or variants in other related genes. Consequently, results should be interpreted in a broader clinical context and possibly supplemented with additional testing, especially in patients with clinical indications for CMT.

Test Details