2025 – PAGE 257 – GENETICS & INHERITED DISEASES

AUTOSOMAL RECESSIVE DISORDERS

NOTE: You are about to move on to the autosomal recessive section. The autosomal recessive disorder mnemonic has some overlap with diseases that start with the letters “T” and “A” from the autosomal dominant mnemonic. Please ensure you have solidified in your mind that Tuberous Sclerosis, Achondroplasia, and Apert Syndrome are autosomal dominant disorders before moving on.

AUTOSOMAL RECESSIVE (AR) DISORDERS PEARLS

• Most inborn errors of metabolism (IEM) are due to autosomal recessive inheritance. Exceptions include Hunters (“X” marks the spot!) and Ornithine TranscarbamylaseDeficiency, both of which are X-linked.
• An AR disorder is ruled out if vertical transmission is noted in three successive generations.
• You are much more likely to be asked to identify a dominant disorder than a recessive disorder. Hopefully the mnemonic below will help you rule out certain diseases when it is clear that the patient has a dominant disorder based on the mode of inheritance.

AUTOSOMAL RECESSIVE MNEMONIC

This autosomal recessive mnemonic is strange but easy to remember: “PAT HAS WACK GAS, which made me HURL in the BACK SEAT of an AUTOmobile!” If you are unfamiliar with PAT, s/he is a unique Saturday Night Live character–Possibly male, possibly female, but definitely full of WACK GAS that would make you HURL in the BACK SEAT of an AUTOmobile!

• PAT: www.pbrlinks.com/AUTORECESSIVE1
• P = PHENYLKETONURIA (AKA PKU)
• A = ALPHA-1-ANTITRYPSIN DEFICIENCY
• T = TAY-SACHS DISEASE
• H & HURL = HURLER’S SYNDROME
• A = ATAXIA TELANGIECTASIA
• S = SICKLE CELL DISEASE and the THALASSEMIAS
• W = WILSONS DISEASE
• A = ALPERS SYNDROME(AKA Progressive Sclerosing Poliodystrophy): This is a progressive neurologic disease. Patients do not meet their milestones and are noted to have ataxia, cognitive deficits, and seizures. They also have liver disease. Patients die by 10 years of age.
  • MNEMONIC: The symptoms of ataxia and cognitive deficits are remarkably similar to how you would feel if you got ALTITUDE sickness in the Swiss ALPS!
• C = CYSTIC FIBROSIS
• K = KARTAGENER SYNDROME: Immotile Cilia & Sperm. Patients have lung issues and are infertile. “While playing KAR-TAG, the muscle man’s CELICA became immotile.”
• G = GALACTOSEMIA
• A = see “A” disorders above
• S = see “S” disorder above
• BACK SEAT = May help you remember that this mnemonic deals with recessive disorders.
• AUTOmobile = AUTOsomal recessive.