[MIM 313 200]

(X-linked spinal and bulbar muscular atrophy, bulbospinal muscular atrophy, SBMA)

Rare: 1/40 000 live male births. X-linked recessive  transmission of an unstable repeat of a CAG triplet (42 to 60) in the AR (androgen receptor) gene (Xq11-q12). Neurodegenerative disease of the lower motor neurons with signs of dysandrogenism.

Women carrying the gene are asymptomatic but discreete signs (cramps,  fasciculations, mild motor deficit) have been reported.

From a genetic point of view, a distinction is made between:

-  type 1[MIM 313,200]:        X-linked recessive transmission of an unstable recurrence of a GAC triplet (42 to 60) at the level of the AR (androgen receptor) gene (Xq11-q12)

-    type 2 [MIM 301 830]:        X-linked recessive transmission of a mutation of the UBA1 gene (Xq11.3)

-    type 3 [MIM 300 489]:        X-linked recessive transmission of a mutation of the ATP7A gene (Xq21.1)

Onset of the first clinical symptoms between 30 and 40 years of age: postural hand tremor (improved by alcohol intake or carrying of a load), muscle pain, progressive amyotrophy, muscle fatigue. Increased CPK blood levels (2 to 4 times the normal level). EMG: neurogenic signs and fasciculations. Occasional fading to repeated stimuli can be observed as in myasthenia.

Then, the bulbar signs appear: successively, speech difficulties (disorders of the articulation), spontaneous laryngospasms, dysphagia and progressive muscular atrophy with fasciculations of the muscles of the tongue and face. Gynecomastia (80 %, sometimes as early as adolescence), erectile dysfunction (50 %) and testicular atrophy appear due to resistance to the androgens and excess of testosterone or progesterone.

There is also a sensitive involvement with loss of the perception of the vibrations.

A few cases of conduction disorders similar to Brugada syndrome (see this term) have been described. Sometimes osteopenia, hypertriglyceridemia.

Pulmonary aspirations at the end of the evolution.

Diagnosis: presence of more than 35 repeats of the CAG triplet on the exon 1 of the AR gene.

Anesthetic implications:

risk of pulmonary aspiration in the perioperative period; careful use of succinylcholine (risk of hyperK+?)  and of non-depolarizing muscle relaxants (increased effect ?) in the presence of muscle atrophy. Monitoring of the curarization (if possible, check the baseline TOF response before administering any myorelaxant). Sugammadex has been used successfully. In the presence of ECG anomalies or a medical history suggestive of a Brugada syndrome are present, refer to this term.

References : 

-        Niesen AD, Sprung J, Prakash YS, Watson JC, Weingarten TN.
Case series: anesthetic management of patients with spinal and bulbar muscular atrophy (Kennedy’s disease).
Can J Anesth 2009; 56: 136-41.

-        Sperfeld AD, Hanemann CO, Ludolph AC, Kassubek J.
Laryngospasm: an underdiagnosed symptom of X-linked spinobulbar muscular atrophy.
Neurology 2005; 64:753–4

-        Takeuchi R, Hoshijima H, Doi K, Nagasaka H.
The use of sugammadex in a patient with Kennedy's disease under general anesthesia.
Saudi J Anaesth. 2014;8: 418–20 

-        Pradat P-F, Bernard E, Corcia P, Couratier P, Jublanc C, Querin G et al.
The French national protocol for Kennedy’s disease (SBMA): consensus diagnostic and management recommendations.
Orphanet J Rare Dis 2020; 15: 90

-        Benarroch L, Bonne G, Rivier F, Hamroun D.
The 2020 version of the gene table of neuromuscular disorders. 
Neuromusc Dis 2019 ; 29 : 980-1018 or http://www.musclegenetable.fr.

Updated: July 2021