Hypovitaminosis D in adolescents has become endemic and often goes unnoticed due to the absence of classic symptoms such as osteomalacia. There is no universally accepted normal vitamin D level; however, some authorities define deficiency as a serum 25-hydroxyvitamin D [25(OH)D] level < 12 ng/mL (<30 nmol/L) and insufficiency as 12 - <20 ng/mL (30 - <50 nmol/L) [1]. Due to lack of consensus, other authorities and laboratories still consider levels of 20 - 29 ng/mL (50 - 74 nmol/L) as insufficient [2][3].

Hypovitaminosis D is more prevalent among adolescents with excess weight, darker skin, limited sunlight exposure, restricted diets, or malabsorption disorders, but it is often overlooked in non-obese individuals [1]. Though more common in older adults, its incidence in adolescents is rising, partly due to decreased outdoor activity and increased nutritional demands during growth and puberty [2][4].

Common symptoms include musculoskeletal complaints; however, atypical neurological symptoms such as acral paresthesia have also been documented [5]. To our knowledge, head tingling has not previously been associated with vitamin D deficiency alone, independent of hypocalcemia. Common causes of head or scalp tingling include neurologic, metabolic, infectious, inflammatory, and psychiatric conditions, as well as deficiencies in vitamins B1, B6, B12, and E [1][6].

This report presents a rare case of severe vitamin D deficiency manifesting primarily as head tingling, sometimes accompanied by extremity tingling, in an adolescent male.

Vitamin D, particularly in its active form calcitriol [1,25(OH)₂D], is now recognized as a neurosteroid hormone involved in neurodevelopment, neurotransmission, and neuroprotection [7][8]. Vitamin D deficiency may disrupt neuronal excitability through altered calcium and chloride channel regulation, leading to peripheral neuropathy and central sensitization [5][7][8].

Vitamin D receptors are widely expressed in peripheral and central neural tissue, where vitamin D regulates neurotrophic factors such as nerve growth factor [9]. Deficiency may impair neuronal survival, growth, and repair, contributing to neuropathic symptoms, including tingling, via direct neuronal excitability or altered sensory processing [9][10]. Vitamin D also modulates inflammatory cytokines, and deficiency may promote neuroinflammation and worsen neuropathic symptoms [10][11]. Recent clinical guidelines recognize vitamin D deficiency’s wider implications, including neuromuscular symptoms like muscle weakness and pain that may indirectly contribute to neurologic complaints such as tingling [11].

This case highlights a rare presentation of severe hypovitaminosis D with normal serum calcium manifesting as head tingling in an adolescent, with complete resolution following vitamin D supplementation. While acral paresthesia and other neurological symptoms have been reported in vitamin D deficiency, head tingling in the absence of hypocalcemia has not been previously described [5][12]-[14]. Other potential tingling causes were thoroughly excluded through clinical evaluation and laboratory testing [1][6].

Unlike prior reports linking paresthesia to hypocalcemia in vitamin D deficiency [4][15], this patient had normal calcium levels, suggesting a direct neurologic effect of vitamin D deficiency. Previous clinical guidelines and trials have reported resolution of paresthesia after correcting vitamin D deficiency with calcium repletion, suggesting a causal role for calcium in those cases [11]. The absence of electrolyte abnormalities, including normal serum calcium, strengthens the hypothesis that vitamin D deficiency itself may contribute to neurologic symptoms rather than acting solely through secondary hypocalcemia. This observation broadens the clinical understanding of hypovitaminosis D and suggests that neurologic symptoms may be an underrecognized manifestation in adolescents.

Additionally, this case supports evidence that serum vitamin D levels below 30 ng/mL may not be optimal, as complete symptom resolution occurred only after levels exceeded this threshold [2][3].

Limitations include inherent constraints of a single-case report, which preclude definitive causal inference. While the temporal relationship between supplementation and symptom resolution is strong, it does not definitively prove causation, and a coincidental recovery cannot be entirely excluded. This case study did not extend beyond the maintenance phase to ensure that tingling did not recur. Further prolonged studies are needed to reinforce the direct correlation between vitamin D deficiency without hypocalcemia and head tingling.

Severe hypovitaminosis D may present with atypical neurological symptoms, including head tingling. The case highlights a direct neurologic effect of vitamin D deficiency rather than an effect of secondary hypocalcemia. It supports consideration of targeted vitamin D evaluation in adolescents presenting with unexplained sensory symptoms or known risk factors. Pediatric clinicians should consider vitamin D deficiency in the differential for unexplained paresthesia and aim at optimal levels above 30 ng/dL when supplementing vitamin D. Screening symptomatic or high-risk adolescents should be emphasized in pediatric practice, regardless of obesity or overweight status.

No funding or sponsorship was received for the publication of this case report. The authors would like to gratefully acknowledge the patient and his mother for their cooperation and agreement to publish this case.

Written informed consent was obtained from the patient’s parent for publication of this case report and any accompanying results.