A male patient presents with sensory loss and weakness of limbs for 3 months. He also has angular stomatitis. On examination, there is loss of proprioception, vibration sensations, UMN type of lower limb weakness, and absent ankle reflex. What is the most probable diagnosis?

Correct Answer: C. Subacute combined degeneration of cord

Subacute combined degeneration (SCD) of the spinal cord is a demyelinating disorder caused by vitamin B12 deficiency, classically presenting with the triad of dorsal column signs (loss of proprioception and vibration sense), corticospinal tract signs (UMN weakness), and peripheral neuropathy signs (absent ankle reflex). The angular stomatitis (cheilitis) is a key clinical clue pointing to B12 deficiency—it reflects glossitis and mucosal changes from nutritional deficiency. The 3-month subacute progression with mixed upper and lower motor neuron signs is pathognomonic. In India, B12 deficiency is common due to vegetarian diets, pernicious anemia, and malabsorption (post-gastrectomy, tropical sprue, Crohn's disease). The combination of dorsal column demyelination (vibration/proprioception loss) + corticospinal tract involvement (UMN weakness) + peripheral nerve involvement (absent reflexes) occurring simultaneously distinguishes SCD from other myelopathies. Early recognition and B12 replacement (IM cyanocobalamin 1000 µg weekly × 6 weeks, then monthly maintenance per Indian guidelines) can halt progression and reverse early neurological deficits.

Why the other options are wrong

A. Multiple sclerosis — MS typically presents with relapsing-remitting course, optic neuritis, internuclear ophthalmoplegia, or brainstem signs in younger patients. While MS can cause mixed motor signs, the absence of visual symptoms, acute relapses, and the presence of angular stomatitis makes it unlikely. MS does not cause nutritional deficiency signs like cheilitis. SCD's subacute progression over months with nutritional clues is distinct from MS. B. Extradural cord compression — Extradural compression (disc, tumor, abscess) typically presents with progressive myelopathy with pain, sensory level, and bladder involvement. The clinical picture here lacks a sensory level and shows mixed UMN/LMN signs without focal cord syndrome features. Angular stomatitis is not a feature of mechanical compression. Imaging (MRI spine) would show a mass; the nutritional history and mucosal signs point away from compression. D. Amyotrophic lateral sclerosis — ALS is a pure motor neuron disease affecting both upper and lower motor neurons, but it does NOT cause sensory loss or loss of proprioception/vibration sense. The presence of dorsal column signs (proprioception, vibration loss) excludes ALS. Angular stomatitis is not a feature of ALS. ALS typically spares sensation entirely, making the sensory component here diagnostic against ALS.

High-Yield Facts

Mnemonics

SCD Clinical Triad DCP = Dorsal column signs (vibration, proprioception) + Corticospinal signs (UMN weakness) + Peripheral neuropathy (absent reflexes). All three present = SCD. B12 Deficiency Mucosal Signs CHAP = Cheilitis (angular stomatitis) + Hyperemia + Atrophic glossitis + Pallor. Any mucosal sign in a myelopathy → think B12.

NBE Trap

NBE may pair "UMN weakness" with ALS to trap students who forget that ALS is a pure motor disease with preserved sensation. The sensory loss (proprioception, vibration) is the discriminator that excludes ALS and points to SCD.

Clinical Pearl

In Indian clinical practice, a vegetarian patient presenting with subacute myelopathy + glossitis should trigger immediate serum B12 and methylmalonic acid levels. Early IM B12 replacement can prevent irreversible spinal cord damage; delayed diagnosis leads to permanent paraplegia. This is a high-yield, reversible cause of myelopathy often missed in primary care.

_Reference: Harrison Ch. 368 (Nutritional and Metabolic Diseases of the Nervous System); Robbins Ch. 28 (Nervous System)_