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?

Explanation

## 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 - **SCD triad**: dorsal column signs (vibration/proprioception loss) + corticospinal tract signs (UMN weakness) + peripheral neuropathy (absent reflexes) occurring together. - **Angular stomatitis (cheilitis)** is a cardinal mucosal sign of B12 deficiency; glossitis and angular cheilitis are pathognomonic nutritional clues. - **Vitamin B12 deficiency in India**: vegetarian diet, pernicious anemia, post-gastrectomy, tropical sprue, and Crohn's disease are common causes. - **IM cyanocobalamin 1000 µg weekly × 6 weeks, then monthly maintenance** is the standard Indian DOC; early treatment can reverse neurological deficits. - **Absent ankle reflex with UMN weakness** indicates combined dorsal column + corticospinal tract + peripheral nerve involvement, pathognomonic for SCD. - **Proprioception and vibration loss** (dorsal column signs) distinguish SCD from ALS, which spares sensation entirely. ## Mnemonics **SCD Clinical Triad** **DCP** = **D**orsal column signs (vibration, proprioception) + **C**orticospinal signs (UMN weakness) + **P**eripheral neuropathy (absent reflexes). All three present = SCD. **B12 Deficiency Mucosal Signs** **CHAP** = **C**heilitis (angular stomatitis) + **H**yperemia + **A**trophic glossitis + **P**allor. 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)_