[MIM 145 600]

(Koussef-Nichols syndrome)

Rare.  Autosomal dominant transmission of a mutation of gene RYR1 (19q13.2), that leads to a risk of malignant hyperthermia.

Clinical features:

-        phenotype resembling Noonan syndrome: high-arched palate, low-set ears, downslanting palpebral fissures, protuberant nose, enlarged upper lip, kyphoscoliosis, chest deformity; sometimes cardiac involvement

-        congenital myopathy (proximal weakness) (unspecific histology), formerly called Evans myopathy. Normal or elevated CPK levels.

-        cases of acute rhabdomyolysis in a context of viral infection have been described

Anesthetic implications:

avoid agents triggering malignant hyperthermia

References : 

-          Maharaj R, Osborne IJS. 
The King-Denborough syndrome in the paediatric patient. 
SAJAA 2007; 13: 27-30.

-          Benca J, Hogan K. 
Malignant hyperthermia, coexisting disorders, and enzymopathies: risks and management options.
Anesth Analg 2009; 109: 1049-53.

-        Joseph MR, Theroux MC, Mooney JJ, Falitz S, Brandom BW, Byler DL.
Intraoperative presentation of malignant hyperthermia (confirmed by RYR1 gene mutation, C7522C>T ; pR2508C) leads to diagnosis of King Denborough syndrome in a child with hypotonia and dysmorphic features.
A & A Case Reports 2017; 8 : 55-7

Updated June 2021