Affected Gene: ABCB1
 Transmission: Autosomal, probably recessive
Mutation: Felis_catus_9.0 A2 g.93144355_93144356 delGA (antisense TC)
 OMIA Link: 001402-9685

Breeds Recommended for Testing: Balinese, Domestic Longhair, Domestic Mediumhair, Domestic Shorthair,  Maine Coon, Ragdoll, Russian Blue, Siamese, Turkish Angora

Symptoms:
Drug hypersensitivity increases the risk of adverse reactions to medications such as ivermectin and macrocyclic lactones due to impaired P-glycoprotein synthesis.
These drugs are commonly found in flea and tick treatments for cats and dogs (Mealey et al., 2023).
Clinical effects may be neurological, including: CNS depression, Ataxia, Seizures, Tremors, Hypersalivation, Vomiting, Mydriasis, Dyspnea. 
In severe cases, it can lead to coma, blindness, and death.
Other reported manifestations include:
Bone marrow suppression (neutropenia, thrombocytopenia), Gastrointestinal toxicity (Mealey et al., 2021)

References:
Mealey KL, Burke NS. Identification of a nonsense mutation in feline ABCB1. J Vet Pharmacol Ther. 2015 Oct;38(5):429-33. DOI: 10.1111/jvp.12212. PMID: 25660379.
Mealey, K.L., Owens, J.G., Freeman, E. Canine and feline P-glycoprotein deficiency: What we know and where we need to go. J Vet Pharmacol Ther, 46:1-16, 2023. DOI: 10.1111/jvp.13102. PMID: 36326478.
Mealey, K.L., Burke, N.S., Villarino, N.F., Court, M.H., Heusser, J.P. Application of eprinomectin-containing parasiticides at label doses causes neurological toxicosis in cats homozygous for ABCB11930_1931del TC. J Vet Pharmacol Ther, 47:226-230, 2024. DOI: 10.1111/jvp.13431. PMID: 38366723.