A 68 year old lady presents to you with left sided hearing impairment. She says that she cannot put the phone on her left ear because it hurts. You perform a physical exam and see that the pinna is not tender but she winces when you put the vibrating tuning fork to her left ear.

You perform a skull X-ray that shows skull bone to be of two different densities. You go on and do a complete lab work up.
CBC shows a white count of 9.2, Hb of 13.4, Platelet count of 389K. Differential count is normal. Sodium is 143, Potassium is 3.9, Chloride is 101, HCO3 is 25, BUN 20 and creatinine is 1.1. Albumin 4.1., Globulin 3.0, AST 38, ALT 20, ALP 349, GGT normal, Bilirubin 0.9mg%.

Q1. Which of the following tests would be most appropriate to detect the origin of the ALP at this point?

GGT (gamma glutamyl transferase)

Rectal examination

Heat lability of ALP

Bence Jones proteinuria

Auditory evoked potential

Answer to Q 1:  "Heat lability of ALP".
Explanation:
ALP (Alkaline phosphatase) comes chiefly from 3 sources - Liver, Bone and placenta. The ALP from bone is not stable in heat and gets burnt/denatured (Bone Burns). This is the method recommended by most labs to check the source of the ALP. In real life we just look at the GGT and see if it is elevated  and if it is elevated then we conclude that the associated rise in ALP is from the liver.

Once one sees that the ALP is from the bone one thinks of a few things

Mets, Osteomalacia or rickets, (Myeloma by itself does not raise the ALP), Fracture and a few not so common diseases. In this patient the Skull X-ray showed variegate bone which is the hallmark of Paget's disease. the most dreaded complication of this disease is osteosarcoma. The osteosarcoma arising in Paget's disease patients is much more nasty and aggressive compared to those arising de-novo. Thus the answer to the following question is Osteosarcoma. The objective of this question was to RECOGNIZE DISEASE PATTERNS and TO DERIVE CLUES FROM THE QUESTIONS themselves. (Deafness-because of temporal bone getting deformed and pressing on the 8th cranial nerve; Raised ALP, Variegate bone on skull Xray. The clue from Q 2 was osteosarcoma as a choice for an answer. Unfortunately a lot of people did not get this question right and I feel that it will be good to stress on pattern recognition)

Q2.  Of the following choices, what complication of this disease is most dreaded in these patients?

Osteosarcoma

Mesothelioma

Dementia

Pheochromocytoma

Acute leukemia